doom3-bfg/neo/renderer/OpenGL/RenderBackend_GL.cpp

/*
===========================================================================

Doom 3 BFG Edition GPL Source Code
Copyright (C) 1993-2012 id Software LLC, a ZeniMax Media company.
Copyright (C) 2013-2019 Robert Beckebans
Copyright (C) 2016-2017 Dustin Land

This file is part of the Doom 3 BFG Edition GPL Source Code ("Doom 3 BFG Edition Source Code").

Doom 3 BFG Edition Source Code is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Doom 3 BFG Edition Source Code is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Doom 3 BFG Edition Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the Doom 3 BFG Edition Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the Doom 3 BFG Edition Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.

===========================================================================
*/

#pragma hdrstop
#include "precompiled.h"

#include "../RenderCommon.h"
#include "../RenderBackend.h"
#include "../../framework/Common_local.h"

idCVar r_drawFlickerBox( "r_drawFlickerBox", "0", CVAR_RENDERER | CVAR_BOOL, "visual test for dropping frames" );
idCVar stereoRender_warp( "stereoRender_warp", "0", CVAR_RENDERER | CVAR_ARCHIVE | CVAR_BOOL, "use the optical warping renderprog instead of stereoDeGhost" );
idCVar stereoRender_warpStrength( "stereoRender_warpStrength", "1.45", CVAR_RENDERER | CVAR_ARCHIVE | CVAR_FLOAT, "amount of pre-distortion" );

idCVar stereoRender_warpCenterX( "stereoRender_warpCenterX", "0.5", CVAR_RENDERER | CVAR_FLOAT | CVAR_ARCHIVE, "center for left eye, right eye will be 1.0 - this" );
idCVar stereoRender_warpCenterY( "stereoRender_warpCenterY", "0.5", CVAR_RENDERER | CVAR_FLOAT | CVAR_ARCHIVE, "center for both eyes" );
idCVar stereoRender_warpParmZ( "stereoRender_warpParmZ", "0", CVAR_RENDERER | CVAR_FLOAT | CVAR_ARCHIVE, "development parm" );
idCVar stereoRender_warpParmW( "stereoRender_warpParmW", "0", CVAR_RENDERER | CVAR_FLOAT | CVAR_ARCHIVE, "development parm" );
idCVar stereoRender_warpTargetFraction( "stereoRender_warpTargetFraction", "1.0", CVAR_RENDERER | CVAR_FLOAT | CVAR_ARCHIVE, "fraction of half-width the through-lens view covers" );

idCVar r_showSwapBuffers( "r_showSwapBuffers", "0", CVAR_BOOL, "Show timings from GL_BlockingSwapBuffers" );
idCVar r_syncEveryFrame( "r_syncEveryFrame", "1", CVAR_BOOL, "Don't let the GPU buffer execution past swapbuffers" );

static int		swapIndex;		// 0 or 1 into renderSync
static GLsync	renderSync[2];

void GLimp_SwapBuffers();
void RB_SetMVP( const idRenderMatrix& mvp );

glContext_t glcontext;

/*
==================
GL_CheckErrors
==================
*/
// RB: added filename, line parms
bool GL_CheckErrors_( const char* filename, int line )
{
	int		err;
	char	s[64];
	int		i;

	if( r_ignoreGLErrors.GetBool() )
	{
		return false;
	}

	// check for up to 10 errors pending
	bool error = false;
	for( i = 0 ; i < 10 ; i++ )
	{
		err = glGetError();
		if( err == GL_NO_ERROR )
		{
			break;
		}

		error = true;
		switch( err )
		{
			case GL_INVALID_ENUM:
				strcpy( s, "GL_INVALID_ENUM" );
				break;
			case GL_INVALID_VALUE:
				strcpy( s, "GL_INVALID_VALUE" );
				break;
			case GL_INVALID_OPERATION:
				strcpy( s, "GL_INVALID_OPERATION" );
				break;
#if !defined(USE_GLES2) && !defined(USE_GLES3)
			case GL_STACK_OVERFLOW:
				strcpy( s, "GL_STACK_OVERFLOW" );
				break;
			case GL_STACK_UNDERFLOW:
				strcpy( s, "GL_STACK_UNDERFLOW" );
				break;
#endif
			case GL_OUT_OF_MEMORY:
				strcpy( s, "GL_OUT_OF_MEMORY" );
				break;
			default:
				idStr::snPrintf( s, sizeof( s ), "%i", err );
				break;
		}

		common->Printf( "caught OpenGL error: %s in file %s line %i\n", s, filename, line );
	}

	return error;
}






/*
========================
DebugCallback

For ARB_debug_output
========================
*/
// RB: added const to userParam
static void CALLBACK DebugCallback( unsigned int source, unsigned int type,
									unsigned int id, unsigned int severity, int length, const char* message, const void* userParam )
{
	// it probably isn't safe to do an idLib::Printf at this point

	// RB: printf should be thread safe on Linux
#if defined(_WIN32)
	OutputDebugString( message );
	OutputDebugString( "\n" );
#else
	printf( "%s\n", message );
#endif
	// RB end
}


/*
==================
R_CheckPortableExtensions
==================
*/
// RB: replaced QGL with GLEW
static void R_CheckPortableExtensions()
{
	glConfig.glVersion = atof( glConfig.version_string );
	const char* badVideoCard = idLocalization::GetString( "#str_06780" );
	if( glConfig.glVersion < 2.0f )
	{
		idLib::FatalError( "%s", badVideoCard );
	}

	if( idStr::Icmpn( glConfig.renderer_string, "ATI ", 4 ) == 0 || idStr::Icmpn( glConfig.renderer_string, "AMD ", 4 ) == 0 )
	{
		glConfig.vendor = VENDOR_AMD;
	}
	else if( idStr::Icmpn( glConfig.renderer_string, "NVIDIA", 6 ) == 0 )
	{
		glConfig.vendor = VENDOR_NVIDIA;
	}
	else if( idStr::Icmpn( glConfig.renderer_string, "Intel", 5 ) == 0 )
	{
		glConfig.vendor = VENDOR_INTEL;
	}

	// RB: Mesa support
	if( idStr::Icmpn( glConfig.renderer_string, "Mesa", 4 ) == 0 || idStr::Icmpn( glConfig.renderer_string, "X.org", 5 ) == 0 || idStr::Icmpn( glConfig.renderer_string, "Gallium", 7 ) == 0 ||
			strcmp( glConfig.vendor_string, "X.Org" ) == 0 ||
			idStr::Icmpn( glConfig.renderer_string, "llvmpipe", 8 ) == 0 )
	{
		if( glConfig.driverType == GLDRV_OPENGL32_CORE_PROFILE )
		{
			glConfig.driverType = GLDRV_OPENGL_MESA_CORE_PROFILE;
		}
		else
		{
			glConfig.driverType = GLDRV_OPENGL_MESA;
		}
	}
	// RB end

	// GL_ARB_multitexture
	if( glConfig.driverType != GLDRV_OPENGL3X )
	{
		glConfig.multitextureAvailable = true;
	}
	else
	{
		glConfig.multitextureAvailable = GLEW_ARB_multitexture != 0;
	}

	// GL_EXT_direct_state_access
	glConfig.directStateAccess = GLEW_EXT_direct_state_access != 0;


	// GL_ARB_texture_compression + GL_S3_s3tc
	// DRI drivers may have GL_ARB_texture_compression but no GL_EXT_texture_compression_s3tc
	if( glConfig.driverType == GLDRV_OPENGL_MESA_CORE_PROFILE )
	{
		glConfig.textureCompressionAvailable = true;
	}
	else
	{
		glConfig.textureCompressionAvailable = GLEW_ARB_texture_compression != 0 && GLEW_EXT_texture_compression_s3tc != 0;
	}
	// GL_EXT_texture_filter_anisotropic
	glConfig.anisotropicFilterAvailable = GLEW_EXT_texture_filter_anisotropic != 0;
	if( glConfig.anisotropicFilterAvailable )
	{
		glGetFloatv( GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &glConfig.maxTextureAnisotropy );
		common->Printf( "   maxTextureAnisotropy: %f\n", glConfig.maxTextureAnisotropy );
	}
	else
	{
		glConfig.maxTextureAnisotropy = 1;
	}

	// GL_EXT_texture_lod_bias
	// The actual extension is broken as specificed, storing the state in the texture unit instead
	// of the texture object.  The behavior in GL 1.4 is the behavior we use.
	glConfig.textureLODBiasAvailable = ( glConfig.glVersion >= 1.4 || GLEW_EXT_texture_lod_bias != 0 );
	if( glConfig.textureLODBiasAvailable )
	{
		common->Printf( "...using %s\n", "GL_EXT_texture_lod_bias" );
	}
	else
	{
		common->Printf( "X..%s not found\n", "GL_EXT_texture_lod_bias" );
	}

	// GL_ARB_seamless_cube_map
	glConfig.seamlessCubeMapAvailable = GLEW_ARB_seamless_cube_map != 0;
	r_useSeamlessCubeMap.SetModified();		// the CheckCvars() next frame will enable / disable it

	// GL_ARB_framebuffer_sRGB
	glConfig.sRGBFramebufferAvailable = GLEW_ARB_framebuffer_sRGB != 0;
	r_useSRGB.SetModified();		// the CheckCvars() next frame will enable / disable it

	// GL_ARB_vertex_buffer_object
	if( glConfig.driverType == GLDRV_OPENGL_MESA_CORE_PROFILE )
	{
		glConfig.vertexBufferObjectAvailable = true;
	}
	else
	{
		glConfig.vertexBufferObjectAvailable = GLEW_ARB_vertex_buffer_object != 0;
	}

	// GL_ARB_map_buffer_range, map a section of a buffer object's data store
	//if( glConfig.driverType == GLDRV_OPENGL_MESA_CORE_PROFILE )
	//{
	//    glConfig.mapBufferRangeAvailable = true;
	//}
	//else
	{
		glConfig.mapBufferRangeAvailable = GLEW_ARB_map_buffer_range != 0;
	}

	// GL_ARB_vertex_array_object
	//if( glConfig.driverType == GLDRV_OPENGL_MESA_CORE_PROFILE )
	//{
	//    glConfig.vertexArrayObjectAvailable = true;
	//}
	//else
	{
		glConfig.vertexArrayObjectAvailable = GLEW_ARB_vertex_array_object != 0;
	}

	// GL_ARB_draw_elements_base_vertex
	glConfig.drawElementsBaseVertexAvailable = GLEW_ARB_draw_elements_base_vertex != 0;

	// GL_ARB_vertex_program / GL_ARB_fragment_program
	glConfig.fragmentProgramAvailable = GLEW_ARB_fragment_program != 0;
	//if( glConfig.fragmentProgramAvailable )
	{
		glGetIntegerv( GL_MAX_TEXTURE_COORDS, ( GLint* )&glConfig.maxTextureCoords );
		glGetIntegerv( GL_MAX_TEXTURE_IMAGE_UNITS, ( GLint* )&glConfig.maxTextureImageUnits );
	}

	// GLSL, core in OpenGL > 2.0
	glConfig.glslAvailable = ( glConfig.glVersion >= 2.0f );

	// GL_ARB_uniform_buffer_object
	glConfig.uniformBufferAvailable = GLEW_ARB_uniform_buffer_object != 0;
	if( glConfig.uniformBufferAvailable )
	{
		glGetIntegerv( GL_UNIFORM_BUFFER_OFFSET_ALIGNMENT, ( GLint* )&glConfig.uniformBufferOffsetAlignment );
		if( glConfig.uniformBufferOffsetAlignment < 256 )
		{
			glConfig.uniformBufferOffsetAlignment = 256;
		}
	}
	// RB: make GPU skinning optional for weak OpenGL drivers
	glConfig.gpuSkinningAvailable = glConfig.uniformBufferAvailable && ( glConfig.driverType == GLDRV_OPENGL3X || glConfig.driverType == GLDRV_OPENGL32_CORE_PROFILE || glConfig.driverType == GLDRV_OPENGL32_COMPATIBILITY_PROFILE );

	// ATI_separate_stencil / OpenGL 2.0 separate stencil
	glConfig.twoSidedStencilAvailable = ( glConfig.glVersion >= 2.0f ) || GLEW_ATI_separate_stencil != 0;

	// GL_EXT_depth_bounds_test
	glConfig.depthBoundsTestAvailable = GLEW_EXT_depth_bounds_test != 0;

	// GL_ARB_sync
	glConfig.syncAvailable = GLEW_ARB_sync &&
							 // as of 5/24/2012 (driver version 15.26.12.64.2761) sync objects
							 // do not appear to work for the Intel HD 4000 graphics
							 ( glConfig.vendor != VENDOR_INTEL || r_skipIntelWorkarounds.GetBool() );

	// GL_ARB_occlusion_query
	glConfig.occlusionQueryAvailable = GLEW_ARB_occlusion_query != 0;

	// GL_ARB_timer_query
	glConfig.timerQueryAvailable = ( GLEW_ARB_timer_query != 0 || GLEW_EXT_timer_query != 0 ) && ( glConfig.vendor != VENDOR_INTEL || r_skipIntelWorkarounds.GetBool() ) && glConfig.driverType != GLDRV_OPENGL_MESA;

	// GREMEDY_string_marker
	glConfig.gremedyStringMarkerAvailable = GLEW_GREMEDY_string_marker != 0;
	if( glConfig.gremedyStringMarkerAvailable )
	{
		common->Printf( "...using %s\n", "GL_GREMEDY_string_marker" );
	}
	else
	{
		common->Printf( "X..%s not found\n", "GL_GREMEDY_string_marker" );
	}

	// KHR_debug
	glConfig.khronosDebugAvailable = GLEW_KHR_debug != 0;
	if( glConfig.khronosDebugAvailable )
	{
		common->Printf( "...using %s\n", "GLEW_KHR_debug" );
	}
	else
	{
		common->Printf( "X..%s not found\n", "GLEW_KHR_debug" );
	}

	// GL_ARB_framebuffer_object
	glConfig.framebufferObjectAvailable = GLEW_ARB_framebuffer_object != 0;
	if( glConfig.framebufferObjectAvailable )
	{
		glGetIntegerv( GL_MAX_RENDERBUFFER_SIZE, &glConfig.maxRenderbufferSize );
		glGetIntegerv( GL_MAX_COLOR_ATTACHMENTS, &glConfig.maxColorAttachments );

		common->Printf( "...using %s\n", "GL_ARB_framebuffer_object" );
	}
	else
	{
		common->Printf( "X..%s not found\n", "GL_ARB_framebuffer_object" );
	}

	// GL_EXT_framebuffer_blit
	glConfig.framebufferBlitAvailable = GLEW_EXT_framebuffer_blit != 0;
	if( glConfig.framebufferBlitAvailable )
	{
		common->Printf( "...using %s\n", "GL_EXT_framebuffer_blit" );
	}
	else
	{
		common->Printf( "X..%s not found\n", "GL_EXT_framebuffer_blit" );
	}

	// GL_ARB_debug_output
	glConfig.debugOutputAvailable = GLEW_ARB_debug_output != 0;
	if( glConfig.debugOutputAvailable )
	{
		if( r_debugContext.GetInteger() >= 1 )
		{
			glDebugMessageCallbackARB( ( GLDEBUGPROCARB ) DebugCallback, NULL );
		}
		if( r_debugContext.GetInteger() >= 2 )
		{
			// force everything to happen in the main thread instead of in a separate driver thread
			glEnable( GL_DEBUG_OUTPUT_SYNCHRONOUS_ARB );
		}
		if( r_debugContext.GetInteger() >= 3 )
		{
			// enable all the low priority messages
			glDebugMessageControlARB( GL_DONT_CARE,
									  GL_DONT_CARE,
									  GL_DEBUG_SEVERITY_LOW_ARB,
									  0, NULL, true );
		}
	}

	// GL_ARB_multitexture
	if( !glConfig.multitextureAvailable )
	{
		idLib::Error( "GL_ARB_multitexture not available" );
	}
	// GL_ARB_texture_compression + GL_EXT_texture_compression_s3tc
	if( !glConfig.textureCompressionAvailable )
	{
		idLib::Error( "GL_ARB_texture_compression or GL_EXT_texture_compression_s3tc not available" );
	}
	// GL_ARB_vertex_buffer_object
	if( !glConfig.vertexBufferObjectAvailable )
	{
		idLib::Error( "GL_ARB_vertex_buffer_object not available" );
	}
	// GL_ARB_map_buffer_range
	if( !glConfig.mapBufferRangeAvailable )
	{
		idLib::Error( "GL_ARB_map_buffer_range not available" );
	}
	// GL_ARB_vertex_array_object
	if( !glConfig.vertexArrayObjectAvailable )
	{
		idLib::Error( "GL_ARB_vertex_array_object not available" );
	}
	// GL_ARB_draw_elements_base_vertex
	if( !glConfig.drawElementsBaseVertexAvailable )
	{
		idLib::Error( "GL_ARB_draw_elements_base_vertex not available" );
	}
	// GL_ARB_vertex_program / GL_ARB_fragment_program
	//if( !glConfig.fragmentProgramAvailable )
	//{
	//	idLib::Warning( "GL_ARB_fragment_program not available" );
	//}
	// GLSL
	if( !glConfig.glslAvailable )
	{
		idLib::Error( "GLSL not available" );
	}
	// GL_ARB_uniform_buffer_object
	if( !glConfig.uniformBufferAvailable )
	{
		idLib::Error( "GL_ARB_uniform_buffer_object not available" );
	}
	// GL_EXT_stencil_two_side
	if( !glConfig.twoSidedStencilAvailable )
	{
		idLib::Error( "GL_ATI_separate_stencil not available" );
	}

	// generate one global Vertex Array Object (VAO)
	glGenVertexArrays( 1, &glConfig.global_vao );
	glBindVertexArray( glConfig.global_vao );
}
// RB end

idStr extensions_string;

/*
==================
R_InitOpenGL

This function is responsible for initializing a valid OpenGL subsystem
for rendering.  This is done by calling the system specific GLimp_Init,
which gives us a working OGL subsystem, then setting all necessary openGL
state, including images, vertex programs, and display lists.

Changes to the vertex cache size or smp state require a vid_restart.

If R_IsInitialized() is false, no rendering can take place, but
all renderSystem functions will still operate properly, notably the material
and model information functions.
==================
*/
void idRenderBackend::Init()
{
	common->Printf( "----- R_InitOpenGL -----\n" );

	if( tr.IsInitialized() )
	{
		common->FatalError( "R_InitOpenGL called while active" );
	}

	// DG: make sure SDL has setup video so getting supported modes in R_SetNewMode() works
	GLimp_PreInit();
	// DG end

	R_SetNewMode( true );

	// input and sound systems need to be tied to the new window
	Sys_InitInput();

	// get our config strings
	glConfig.vendor_string = ( const char* )glGetString( GL_VENDOR );
	glConfig.renderer_string = ( const char* )glGetString( GL_RENDERER );
	glConfig.version_string = ( const char* )glGetString( GL_VERSION );
	glConfig.shading_language_string = ( const char* )glGetString( GL_SHADING_LANGUAGE_VERSION );
	glConfig.extensions_string = ( const char* )glGetString( GL_EXTENSIONS );

	if( glConfig.extensions_string == NULL )
	{
		// As of OpenGL 3.2, glGetStringi is required to obtain the available extensions
		//glGetStringi = ( PFNGLGETSTRINGIPROC )GLimp_ExtensionPointer( "glGetStringi" );

		// Build the extensions string
		GLint numExtensions;
		glGetIntegerv( GL_NUM_EXTENSIONS, &numExtensions );
		extensions_string.Clear();
		for( int i = 0; i < numExtensions; i++ )
		{
			extensions_string.Append( ( const char* )glGetStringi( GL_EXTENSIONS, i ) );
			// the now deprecated glGetString method usaed to create a single string with each extension separated by a space
			if( i < numExtensions - 1 )
			{
				extensions_string.Append( ' ' );
			}
		}
		glConfig.extensions_string = extensions_string.c_str();
	}


	float glVersion = atof( glConfig.version_string );
	float glslVersion = atof( glConfig.shading_language_string );
	idLib::Printf( "OpenGL Version   : %3.1f\n", glVersion );
	idLib::Printf( "OpenGL Vendor    : %s\n", glConfig.vendor_string );
	idLib::Printf( "OpenGL Renderer  : %s\n", glConfig.renderer_string );
	idLib::Printf( "OpenGL GLSL      : %3.1f\n", glslVersion );
	idLib::Printf( "OpenGL Extensions: %s\n", glConfig.extensions_string );

	// OpenGL driver constants
	GLint temp;
	glGetIntegerv( GL_MAX_TEXTURE_SIZE, &temp );
	glConfig.maxTextureSize = temp;

	// stubbed or broken drivers may have reported 0...
	if( glConfig.maxTextureSize <= 0 )
	{
		glConfig.maxTextureSize = 256;
	}

	// recheck all the extensions (FIXME: this might be dangerous)
	R_CheckPortableExtensions();

	renderProgManager.Init();

	tr.SetInitialized();

	// allocate the vertex array range or vertex objects
	vertexCache.Init( glConfig.uniformBufferOffsetAlignment );

	// allocate the frame data, which may be more if smp is enabled
	R_InitFrameData();

	// Reset our gamma
	R_SetColorMappings();

	// RB: prepare ImGui system
	ImGui_Init();
}

void idRenderBackend::Shutdown()
{
	ImGui_Shutdown();

	GLimp_Shutdown();
}

/*
=============
idRenderBackend::DrawElementsWithCounters
=============
*/
void idRenderBackend::DrawElementsWithCounters( const drawSurf_t* surf )
{
	// get vertex buffer
	const vertCacheHandle_t vbHandle = surf->ambientCache;
	idVertexBuffer* vertexBuffer;
	if( vertexCache.CacheIsStatic( vbHandle ) )
	{
		vertexBuffer = &vertexCache.staticData.vertexBuffer;
	}
	else
	{
		const uint64 frameNum = ( int )( vbHandle >> VERTCACHE_FRAME_SHIFT ) & VERTCACHE_FRAME_MASK;
		if( frameNum != ( ( vertexCache.currentFrame - 1 ) & VERTCACHE_FRAME_MASK ) )
		{
			idLib::Warning( "RB_DrawElementsWithCounters, vertexBuffer == NULL" );
			return;
		}
		vertexBuffer = &vertexCache.frameData[vertexCache.drawListNum].vertexBuffer;
	}
	const int vertOffset = ( int )( vbHandle >> VERTCACHE_OFFSET_SHIFT ) & VERTCACHE_OFFSET_MASK;

	// get index buffer
	const vertCacheHandle_t ibHandle = surf->indexCache;
	idIndexBuffer* indexBuffer;
	if( vertexCache.CacheIsStatic( ibHandle ) )
	{
		indexBuffer = &vertexCache.staticData.indexBuffer;
	}
	else
	{
		const uint64 frameNum = ( int )( ibHandle >> VERTCACHE_FRAME_SHIFT ) & VERTCACHE_FRAME_MASK;
		if( frameNum != ( ( vertexCache.currentFrame - 1 ) & VERTCACHE_FRAME_MASK ) )
		{
			idLib::Warning( "RB_DrawElementsWithCounters, indexBuffer == NULL" );
			return;
		}
		indexBuffer = &vertexCache.frameData[vertexCache.drawListNum].indexBuffer;
	}
	// RB: 64 bit fixes, changed int to GLintptr
	const GLintptr indexOffset = ( GLintptr )( ibHandle >> VERTCACHE_OFFSET_SHIFT ) & VERTCACHE_OFFSET_MASK;
	// RB end

	RENDERLOG_PRINTF( "Binding Buffers: %p:%i %p:%i\n", vertexBuffer, vertOffset, indexBuffer, indexOffset );

	if( surf->jointCache )
	{
		// DG: this happens all the time in the erebus1 map with blendlight.vfp,
		// so don't call assert (through verify) here until it's fixed (if fixable)
		// else the game crashes on linux when using debug builds

		// FIXME: fix this properly if possible?
		// RB: yes but it would require an additional blend light skinned shader
		//if( !verify( renderProgManager.ShaderUsesJoints() ) )
		if( !renderProgManager.ShaderUsesJoints() )
			// DG end
		{
			return;
		}
	}
	else
	{
		if( !verify( !renderProgManager.ShaderUsesJoints() || renderProgManager.ShaderHasOptionalSkinning() ) )
		{
			return;
		}
	}


	if( surf->jointCache )
	{
		idUniformBuffer jointBuffer;
		if( !vertexCache.GetJointBuffer( surf->jointCache, &jointBuffer ) )
		{
			idLib::Warning( "RB_DrawElementsWithCounters, jointBuffer == NULL" );
			return;
		}
		assert( ( jointBuffer.GetOffset() & ( glConfig.uniformBufferOffsetAlignment - 1 ) ) == 0 );

		// RB: 64 bit fixes, changed GLuint to GLintptr
		const GLintptr ubo = jointBuffer.GetAPIObject();
		// RB end

		glBindBufferRange( GL_UNIFORM_BUFFER, 0, ubo, jointBuffer.GetOffset(), jointBuffer.GetSize() );
	}

	renderProgManager.CommitUniforms( glStateBits );

	// RB: 64 bit fixes, changed GLuint to GLintptr
	if( currentIndexBuffer != ( GLintptr )indexBuffer->GetAPIObject() || !r_useStateCaching.GetBool() )
	{
		glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, ( GLintptr )indexBuffer->GetAPIObject() );
		currentIndexBuffer = ( GLintptr )indexBuffer->GetAPIObject();
	}

	if( ( vertexLayout != LAYOUT_DRAW_VERT ) || ( currentVertexBuffer != ( GLintptr )vertexBuffer->GetAPIObject() ) || !r_useStateCaching.GetBool() )
	{
		glBindBuffer( GL_ARRAY_BUFFER, ( GLintptr )vertexBuffer->GetAPIObject() );
		currentVertexBuffer = ( GLintptr )vertexBuffer->GetAPIObject();

		glEnableVertexAttribArray( PC_ATTRIB_INDEX_VERTEX );
		glEnableVertexAttribArray( PC_ATTRIB_INDEX_NORMAL );
		glEnableVertexAttribArray( PC_ATTRIB_INDEX_COLOR );
		glEnableVertexAttribArray( PC_ATTRIB_INDEX_COLOR2 );
		glEnableVertexAttribArray( PC_ATTRIB_INDEX_ST );
		glEnableVertexAttribArray( PC_ATTRIB_INDEX_TANGENT );

		glVertexAttribPointer( PC_ATTRIB_INDEX_VERTEX, 3, GL_FLOAT, GL_FALSE, sizeof( idDrawVert ), ( void* )( DRAWVERT_XYZ_OFFSET ) );
		glVertexAttribPointer( PC_ATTRIB_INDEX_NORMAL, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idDrawVert ), ( void* )( DRAWVERT_NORMAL_OFFSET ) );
		glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idDrawVert ), ( void* )( DRAWVERT_COLOR_OFFSET ) );
		glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR2, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idDrawVert ), ( void* )( DRAWVERT_COLOR2_OFFSET ) );
		glVertexAttribPointer( PC_ATTRIB_INDEX_ST, 2, GL_HALF_FLOAT, GL_TRUE, sizeof( idDrawVert ), ( void* )( DRAWVERT_ST_OFFSET ) );
		glVertexAttribPointer( PC_ATTRIB_INDEX_TANGENT, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idDrawVert ), ( void* )( DRAWVERT_TANGENT_OFFSET ) );

		vertexLayout = LAYOUT_DRAW_VERT;
	}
	// RB end

	glDrawElementsBaseVertex( GL_TRIANGLES,
							  r_singleTriangle.GetBool() ? 3 : surf->numIndexes,
							  GL_INDEX_TYPE,
							  ( triIndex_t* )indexOffset,
							  vertOffset / sizeof( idDrawVert ) );

	// RB: added stats
	pc.c_drawElements++;
	pc.c_drawIndexes += surf->numIndexes;
}

/*
=========================================================================================================

GL COMMANDS

=========================================================================================================
*/

/*
==================
idRenderBackend::GL_StartFrame
==================
*/
void idRenderBackend::GL_StartFrame()
{
	// If we have a stereo pixel format, this will draw to both
	// the back left and back right buffers, which will have a
	// performance penalty.
	glDrawBuffer( GL_BACK );
}

/*
==================
idRenderBackend::GL_EndFrame
==================
*/
void idRenderBackend::GL_EndFrame()
{
	// Fix for the steam overlay not showing up while in game without Shell/Debug/Console/Menu also rendering
	glColorMask( 1, 1, 1, 1 );

	glFlush();
}

/*
=============
GL_BlockingSwapBuffers

We want to exit this with the GPU idle, right at vsync
=============
*/
void idRenderBackend::GL_BlockingSwapBuffers()
{
	RENDERLOG_PRINTF( "***************** GL_BlockingSwapBuffers *****************\n\n\n" );

	const int beforeFinish = Sys_Milliseconds();

	if( !glConfig.syncAvailable )
	{
		glFinish();
	}

	const int beforeSwap = Sys_Milliseconds();
	if( r_showSwapBuffers.GetBool() && beforeSwap - beforeFinish > 1 )
	{
		common->Printf( "%i msec to glFinish\n", beforeSwap - beforeFinish );
	}

	GLimp_SwapBuffers();

	const int beforeFence = Sys_Milliseconds();
	if( r_showSwapBuffers.GetBool() && beforeFence - beforeSwap > 1 )
	{
		common->Printf( "%i msec to swapBuffers\n", beforeFence - beforeSwap );
	}

	if( glConfig.syncAvailable )
	{
		swapIndex ^= 1;

		if( glIsSync( renderSync[swapIndex] ) )
		{
			glDeleteSync( renderSync[swapIndex] );
		}
		// draw something tiny to ensure the sync is after the swap
		const int start = Sys_Milliseconds();
		glScissor( 0, 0, 1, 1 );
		glEnable( GL_SCISSOR_TEST );
		glClear( GL_COLOR_BUFFER_BIT );
		renderSync[swapIndex] = glFenceSync( GL_SYNC_GPU_COMMANDS_COMPLETE, 0 );
		const int end = Sys_Milliseconds();
		if( r_showSwapBuffers.GetBool() && end - start > 1 )
		{
			common->Printf( "%i msec to start fence\n", end - start );
		}

		GLsync	syncToWaitOn;
		if( r_syncEveryFrame.GetBool() )
		{
			syncToWaitOn = renderSync[swapIndex];
		}
		else
		{
			syncToWaitOn = renderSync[!swapIndex];
		}

		if( glIsSync( syncToWaitOn ) )
		{
			for( GLenum r = GL_TIMEOUT_EXPIRED; r == GL_TIMEOUT_EXPIRED; )
			{
				r = glClientWaitSync( syncToWaitOn, GL_SYNC_FLUSH_COMMANDS_BIT, 1000 * 1000 );
			}
		}
	}

	const int afterFence = Sys_Milliseconds();
	if( r_showSwapBuffers.GetBool() && afterFence - beforeFence > 1 )
	{
		common->Printf( "%i msec to wait on fence\n", afterFence - beforeFence );
	}

	const int64 exitBlockTime = Sys_Microseconds();

	static int64 prevBlockTime;
	if( r_showSwapBuffers.GetBool() && prevBlockTime )
	{
		const int delta = ( int )( exitBlockTime - prevBlockTime );
		common->Printf( "blockToBlock: %i\n", delta );
	}
	prevBlockTime = exitBlockTime;
}

/*
========================
GL_SetDefaultState

This should initialize all GL state that any part of the entire program
may touch, including the editor.
========================
*/
void idRenderBackend::GL_SetDefaultState()
{
	RENDERLOG_PRINTF( "--- GL_SetDefaultState ---\n" );

	glClearDepth( 1.0f );

	// make sure our GL state vector is set correctly
	memset( &glcontext.tmu, 0, sizeof( glcontext.tmu ) );
	currenttmu = 0;
	currentVertexBuffer = 0;
	currentIndexBuffer = 0;
	currentFramebuffer = 0;
	vertexLayout = LAYOUT_UNKNOWN;
	polyOfsScale = 0.0f;
	polyOfsBias = 0.0f;
	glStateBits = 0;

	hdrAverageLuminance = 0;
	hdrMaxLuminance = 0;
	hdrTime = 0;
	hdrKey = 0;

	GL_State( 0, true );

	// RB begin
	Framebuffer::Unbind();
	// RB end

#if 0
	// These are changed by GL_Cull
	glCullFace( GL_FRONT_AND_BACK );
	glEnable( GL_CULL_FACE );

	// These are changed by GL_State
	glColorMask( GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE );
	glBlendFunc( GL_ONE, GL_ZERO );
	glDepthMask( GL_TRUE );
	glDepthFunc( GL_LESS );
	glDisable( GL_STENCIL_TEST );
	glDisable( GL_POLYGON_OFFSET_FILL );
	glDisable( GL_POLYGON_OFFSET_LINE );
	glPolygonMode( GL_FRONT_AND_BACK, GL_FILL );
#endif

	// These should never be changed
	// DG: deprecated in opengl 3.2 and not needed because we don't do fixed function pipeline
	// glShadeModel( GL_SMOOTH );
	// DG end
	glEnable( GL_DEPTH_TEST );
	glEnable( GL_BLEND );
	glEnable( GL_SCISSOR_TEST );
	glDrawBuffer( GL_BACK );
	glReadBuffer( GL_BACK );

	if( r_useScissor.GetBool() )
	{
		glScissor( 0, 0, renderSystem->GetWidth(), renderSystem->GetHeight() );
	}

	// RB: don't keep renderprogs that were enabled during level load
	renderProgManager.Unbind();
	// RB end
}

/*
====================
idRenderBackend::GL_State

This routine is responsible for setting the most commonly changed state
====================
*/
void idRenderBackend::GL_State( uint64 stateBits, bool forceGlState )
{
	uint64 diff = stateBits ^ glStateBits;

	if( !r_useStateCaching.GetBool() || forceGlState )
	{
		// make sure everything is set all the time, so we
		// can see if our delta checking is screwing up
		diff = 0xFFFFFFFFFFFFFFFF;
	}
	else if( diff == 0 )
	{
		return;
	}

	//
	// culling
	//
	if( diff & ( GLS_CULL_BITS ) )//| GLS_MIRROR_VIEW ) )
	{
		switch( stateBits & GLS_CULL_BITS )
		{
			case GLS_CULL_TWOSIDED:
				glDisable( GL_CULL_FACE );
				break;

			case GLS_CULL_BACKSIDED:
				glEnable( GL_CULL_FACE );
				if( viewDef != NULL && viewDef->isMirror )
				{
					stateBits |= GLS_MIRROR_VIEW;
					glCullFace( GL_FRONT );
				}
				else
				{
					glCullFace( GL_BACK );
				}
				break;

			case GLS_CULL_FRONTSIDED:
			default:
				glEnable( GL_CULL_FACE );
				if( viewDef != NULL && viewDef->isMirror )
				{
					stateBits |= GLS_MIRROR_VIEW;
					glCullFace( GL_BACK );
				}
				else
				{
					glCullFace( GL_FRONT );
				}
				break;
		}
	}

	//
	// check depthFunc bits
	//
	if( diff & GLS_DEPTHFUNC_BITS )
	{
		switch( stateBits & GLS_DEPTHFUNC_BITS )
		{
			case GLS_DEPTHFUNC_EQUAL:
				glDepthFunc( GL_EQUAL );
				break;
			case GLS_DEPTHFUNC_ALWAYS:
				glDepthFunc( GL_ALWAYS );
				break;
			case GLS_DEPTHFUNC_LESS:
				glDepthFunc( GL_LEQUAL );
				break;
			case GLS_DEPTHFUNC_GREATER:
				glDepthFunc( GL_GEQUAL );
				break;
		}
	}

	//
	// check blend bits
	//
	if( diff & ( GLS_SRCBLEND_BITS | GLS_DSTBLEND_BITS ) )
	{
		GLenum srcFactor = GL_ONE;
		GLenum dstFactor = GL_ZERO;

		switch( stateBits & GLS_SRCBLEND_BITS )
		{
			case GLS_SRCBLEND_ZERO:
				srcFactor = GL_ZERO;
				break;
			case GLS_SRCBLEND_ONE:
				srcFactor = GL_ONE;
				break;
			case GLS_SRCBLEND_DST_COLOR:
				srcFactor = GL_DST_COLOR;
				break;
			case GLS_SRCBLEND_ONE_MINUS_DST_COLOR:
				srcFactor = GL_ONE_MINUS_DST_COLOR;
				break;
			case GLS_SRCBLEND_SRC_ALPHA:
				srcFactor = GL_SRC_ALPHA;
				break;
			case GLS_SRCBLEND_ONE_MINUS_SRC_ALPHA:
				srcFactor = GL_ONE_MINUS_SRC_ALPHA;
				break;
			case GLS_SRCBLEND_DST_ALPHA:
				srcFactor = GL_DST_ALPHA;
				break;
			case GLS_SRCBLEND_ONE_MINUS_DST_ALPHA:
				srcFactor = GL_ONE_MINUS_DST_ALPHA;
				break;
			default:
				assert( !"GL_State: invalid src blend state bits\n" );
				break;
		}

		switch( stateBits & GLS_DSTBLEND_BITS )
		{
			case GLS_DSTBLEND_ZERO:
				dstFactor = GL_ZERO;
				break;
			case GLS_DSTBLEND_ONE:
				dstFactor = GL_ONE;
				break;
			case GLS_DSTBLEND_SRC_COLOR:
				dstFactor = GL_SRC_COLOR;
				break;
			case GLS_DSTBLEND_ONE_MINUS_SRC_COLOR:
				dstFactor = GL_ONE_MINUS_SRC_COLOR;
				break;
			case GLS_DSTBLEND_SRC_ALPHA:
				dstFactor = GL_SRC_ALPHA;
				break;
			case GLS_DSTBLEND_ONE_MINUS_SRC_ALPHA:
				dstFactor = GL_ONE_MINUS_SRC_ALPHA;
				break;
			case GLS_DSTBLEND_DST_ALPHA:
				dstFactor = GL_DST_ALPHA;
				break;
			case GLS_DSTBLEND_ONE_MINUS_DST_ALPHA:
				dstFactor = GL_ONE_MINUS_DST_ALPHA;
				break;
			default:
				assert( !"GL_State: invalid dst blend state bits\n" );
				break;
		}

		// Only actually update GL's blend func if blending is enabled.
		if( srcFactor == GL_ONE && dstFactor == GL_ZERO )
		{
			glDisable( GL_BLEND );
		}
		else
		{
			glEnable( GL_BLEND );
			glBlendFunc( srcFactor, dstFactor );
		}
	}

	//
	// check depthmask
	//
	if( diff & GLS_DEPTHMASK )
	{
		if( stateBits & GLS_DEPTHMASK )
		{
			glDepthMask( GL_FALSE );
		}
		else
		{
			glDepthMask( GL_TRUE );
		}
	}

	//
	// check colormask
	//
	if( diff & ( GLS_REDMASK | GLS_GREENMASK | GLS_BLUEMASK | GLS_ALPHAMASK ) )
	{
		GLboolean r = ( stateBits & GLS_REDMASK ) ? GL_FALSE : GL_TRUE;
		GLboolean g = ( stateBits & GLS_GREENMASK ) ? GL_FALSE : GL_TRUE;
		GLboolean b = ( stateBits & GLS_BLUEMASK ) ? GL_FALSE : GL_TRUE;
		GLboolean a = ( stateBits & GLS_ALPHAMASK ) ? GL_FALSE : GL_TRUE;
		glColorMask( r, g, b, a );
	}

	//
	// fill/line mode
	//
	if( diff & GLS_POLYMODE_LINE )
	{
		if( stateBits & GLS_POLYMODE_LINE )
		{
			glPolygonMode( GL_FRONT_AND_BACK, GL_LINE );
		}
		else
		{
			glPolygonMode( GL_FRONT_AND_BACK, GL_FILL );
		}
	}

	//
	// polygon offset
	//
	if( diff & GLS_POLYGON_OFFSET )
	{
		if( stateBits & GLS_POLYGON_OFFSET )
		{
			glPolygonOffset( polyOfsScale, polyOfsBias );
			glEnable( GL_POLYGON_OFFSET_FILL );
			glEnable( GL_POLYGON_OFFSET_LINE );
		}
		else
		{
			glDisable( GL_POLYGON_OFFSET_FILL );
			glDisable( GL_POLYGON_OFFSET_LINE );
		}
	}

	//
	// stencil
	//
	if( diff & ( GLS_STENCIL_FUNC_BITS | GLS_STENCIL_OP_BITS ) )
	{
		if( ( stateBits & ( GLS_STENCIL_FUNC_BITS | GLS_STENCIL_OP_BITS ) ) != 0 )
		{
			glEnable( GL_STENCIL_TEST );
		}
		else
		{
			glDisable( GL_STENCIL_TEST );
		}
	}
	if( diff & ( GLS_STENCIL_FUNC_BITS | GLS_STENCIL_FUNC_REF_BITS | GLS_STENCIL_FUNC_MASK_BITS ) )
	{
		GLuint ref = GLuint( ( stateBits & GLS_STENCIL_FUNC_REF_BITS ) >> GLS_STENCIL_FUNC_REF_SHIFT );
		GLuint mask = GLuint( ( stateBits & GLS_STENCIL_FUNC_MASK_BITS ) >> GLS_STENCIL_FUNC_MASK_SHIFT );
		GLenum func = 0;

		switch( stateBits & GLS_STENCIL_FUNC_BITS )
		{
			case GLS_STENCIL_FUNC_NEVER:
				func = GL_NEVER;
				break;
			case GLS_STENCIL_FUNC_LESS:
				func = GL_LESS;
				break;
			case GLS_STENCIL_FUNC_EQUAL:
				func = GL_EQUAL;
				break;
			case GLS_STENCIL_FUNC_LEQUAL:
				func = GL_LEQUAL;
				break;
			case GLS_STENCIL_FUNC_GREATER:
				func = GL_GREATER;
				break;
			case GLS_STENCIL_FUNC_NOTEQUAL:
				func = GL_NOTEQUAL;
				break;
			case GLS_STENCIL_FUNC_GEQUAL:
				func = GL_GEQUAL;
				break;
			case GLS_STENCIL_FUNC_ALWAYS:
				func = GL_ALWAYS;
				break;
		}
		glStencilFunc( func, ref, mask );
	}
	if( diff & ( GLS_STENCIL_OP_FAIL_BITS | GLS_STENCIL_OP_ZFAIL_BITS | GLS_STENCIL_OP_PASS_BITS ) )
	{
		GLenum sFail = 0;
		GLenum zFail = 0;
		GLenum pass = 0;

		switch( stateBits & GLS_STENCIL_OP_FAIL_BITS )
		{
			case GLS_STENCIL_OP_FAIL_KEEP:
				sFail = GL_KEEP;
				break;
			case GLS_STENCIL_OP_FAIL_ZERO:
				sFail = GL_ZERO;
				break;
			case GLS_STENCIL_OP_FAIL_REPLACE:
				sFail = GL_REPLACE;
				break;
			case GLS_STENCIL_OP_FAIL_INCR:
				sFail = GL_INCR;
				break;
			case GLS_STENCIL_OP_FAIL_DECR:
				sFail = GL_DECR;
				break;
			case GLS_STENCIL_OP_FAIL_INVERT:
				sFail = GL_INVERT;
				break;
			case GLS_STENCIL_OP_FAIL_INCR_WRAP:
				sFail = GL_INCR_WRAP;
				break;
			case GLS_STENCIL_OP_FAIL_DECR_WRAP:
				sFail = GL_DECR_WRAP;
				break;
		}
		switch( stateBits & GLS_STENCIL_OP_ZFAIL_BITS )
		{
			case GLS_STENCIL_OP_ZFAIL_KEEP:
				zFail = GL_KEEP;
				break;
			case GLS_STENCIL_OP_ZFAIL_ZERO:
				zFail = GL_ZERO;
				break;
			case GLS_STENCIL_OP_ZFAIL_REPLACE:
				zFail = GL_REPLACE;
				break;
			case GLS_STENCIL_OP_ZFAIL_INCR:
				zFail = GL_INCR;
				break;
			case GLS_STENCIL_OP_ZFAIL_DECR:
				zFail = GL_DECR;
				break;
			case GLS_STENCIL_OP_ZFAIL_INVERT:
				zFail = GL_INVERT;
				break;
			case GLS_STENCIL_OP_ZFAIL_INCR_WRAP:
				zFail = GL_INCR_WRAP;
				break;
			case GLS_STENCIL_OP_ZFAIL_DECR_WRAP:
				zFail = GL_DECR_WRAP;
				break;
		}
		switch( stateBits & GLS_STENCIL_OP_PASS_BITS )
		{
			case GLS_STENCIL_OP_PASS_KEEP:
				pass = GL_KEEP;
				break;
			case GLS_STENCIL_OP_PASS_ZERO:
				pass = GL_ZERO;
				break;
			case GLS_STENCIL_OP_PASS_REPLACE:
				pass = GL_REPLACE;
				break;
			case GLS_STENCIL_OP_PASS_INCR:
				pass = GL_INCR;
				break;
			case GLS_STENCIL_OP_PASS_DECR:
				pass = GL_DECR;
				break;
			case GLS_STENCIL_OP_PASS_INVERT:
				pass = GL_INVERT;
				break;
			case GLS_STENCIL_OP_PASS_INCR_WRAP:
				pass = GL_INCR_WRAP;
				break;
			case GLS_STENCIL_OP_PASS_DECR_WRAP:
				pass = GL_DECR_WRAP;
				break;
		}
		glStencilOp( sFail, zFail, pass );
	}

	glStateBits = stateBits;
}

/*
====================
idRenderBackend::SelectTexture
====================
*/
void idRenderBackend::GL_SelectTexture( int unit )
{
	if( currenttmu == unit )
	{
		return;
	}

	if( unit < 0 || unit >= glConfig.maxTextureImageUnits )
	{
		common->Warning( "GL_SelectTexture: unit = %i", unit );
		return;
	}

	RENDERLOG_PRINTF( "GL_SelectTexture( %i );\n", unit );

	currenttmu = unit;
}



/*
====================
idRenderBackend::GL_Scissor
====================
*/
void idRenderBackend::GL_Scissor( int x /* left*/, int y /* bottom */, int w, int h )
{
	glScissor( x, y, w, h );
}

/*
====================
idRenderBackend::GL_Viewport
====================
*/
void idRenderBackend::GL_Viewport( int x /* left */, int y /* bottom */, int w, int h )
{
	glViewport( x, y, w, h );
}

/*
====================
idRenderBackend::GL_PolygonOffset
====================
*/
void idRenderBackend::GL_PolygonOffset( float scale, float bias )
{
	polyOfsScale = scale;
	polyOfsBias = bias;

	if( glStateBits & GLS_POLYGON_OFFSET )
	{
		glPolygonOffset( scale, bias );
	}
}

/*
========================
idRenderBackend::GL_DepthBoundsTest
========================
*/
void idRenderBackend::GL_DepthBoundsTest( const float zmin, const float zmax )
{
	if( !glConfig.depthBoundsTestAvailable || zmin > zmax )
	{
		return;
	}

	if( zmin == 0.0f && zmax == 0.0f )
	{
		glDisable( GL_DEPTH_BOUNDS_TEST_EXT );
	}
	else
	{
		glEnable( GL_DEPTH_BOUNDS_TEST_EXT );
		glDepthBoundsEXT( zmin, zmax );
	}
}

/*
====================
idRenderBackend::GL_Color
====================
*/
void idRenderBackend::GL_Color( float r, float g, float b, float a )
{
	float parm[4];
	parm[0] = idMath::ClampFloat( 0.0f, 1.0f, r );
	parm[1] = idMath::ClampFloat( 0.0f, 1.0f, g );
	parm[2] = idMath::ClampFloat( 0.0f, 1.0f, b );
	parm[3] = idMath::ClampFloat( 0.0f, 1.0f, a );
	renderProgManager.SetRenderParm( RENDERPARM_COLOR, parm );
}

/*
========================
idRenderBackend::GL_Clear
========================
*/
void idRenderBackend::GL_Clear( bool color, bool depth, bool stencil, byte stencilValue, float r, float g, float b, float a, bool clearHDR )
{
	int clearFlags = 0;
	if( color )
	{
		glClearColor( r, g, b, a );
		clearFlags |= GL_COLOR_BUFFER_BIT;
	}
	if( depth )
	{
		clearFlags |= GL_DEPTH_BUFFER_BIT;
	}
	if( stencil )
	{
		glClearStencil( stencilValue );
		clearFlags |= GL_STENCIL_BUFFER_BIT;
	}
	glClear( clearFlags );

	// RB begin
	if( r_useHDR.GetBool() && clearHDR && globalFramebuffers.hdrFBO != NULL )
	{
		bool isDefaultFramebufferActive = Framebuffer::IsDefaultFramebufferActive();

		globalFramebuffers.hdrFBO->Bind();
		glClear( clearFlags );

		if( isDefaultFramebufferActive )
		{
			Framebuffer::Unbind();
		}
	}
	// RB end
}


/*
=================
idRenderBackend::GL_GetCurrentState
=================
*/
uint64 idRenderBackend::GL_GetCurrentState() const
{
	return glStateBits;
}

/*
========================
idRenderBackend::GL_GetCurrentStateMinusStencil
========================
*/
uint64 idRenderBackend::GL_GetCurrentStateMinusStencil() const
{
	return GL_GetCurrentState() & ~( GLS_STENCIL_OP_BITS | GLS_STENCIL_FUNC_BITS | GLS_STENCIL_FUNC_REF_BITS | GLS_STENCIL_FUNC_MASK_BITS );
}


/*
=============
idRenderBackend::CheckCVars

See if some cvars that we watch have changed
=============
*/
void idRenderBackend::CheckCVars()
{
	// gamma stuff
	if( r_gamma.IsModified() || r_brightness.IsModified() )
	{
		r_gamma.ClearModified();
		r_brightness.ClearModified();
		R_SetColorMappings();
	}

	// filtering
	if( r_maxAnisotropicFiltering.IsModified() || r_useTrilinearFiltering.IsModified() || r_lodBias.IsModified() )
	{
		idLib::Printf( "Updating texture filter parameters.\n" );
		r_maxAnisotropicFiltering.ClearModified();
		r_useTrilinearFiltering.ClearModified();
		r_lodBias.ClearModified();

		for( int i = 0 ; i < globalImages->images.Num() ; i++ )
		{
			if( globalImages->images[i] )
			{
				globalImages->images[i]->Bind();
				globalImages->images[i]->SetTexParameters();
			}
		}
	}

	if( r_useSeamlessCubeMap.IsModified() )
	{
		r_useSeamlessCubeMap.ClearModified();
		if( glConfig.seamlessCubeMapAvailable )
		{
			if( r_useSeamlessCubeMap.GetBool() )
			{
				glEnable( GL_TEXTURE_CUBE_MAP_SEAMLESS );
			}
			else
			{
				glDisable( GL_TEXTURE_CUBE_MAP_SEAMLESS );
			}
		}
	}

	if( r_useSRGB.IsModified() )
	{
		r_useSRGB.ClearModified();
		if( glConfig.sRGBFramebufferAvailable )
		{
			if( r_useSRGB.GetBool() && r_useSRGB.GetInteger() != 3 )
			{
				glEnable( GL_FRAMEBUFFER_SRGB );
			}
			else
			{
				glDisable( GL_FRAMEBUFFER_SRGB );
			}
		}
	}

	if( r_antiAliasing.IsModified() )
	{
		switch( r_antiAliasing.GetInteger() )
		{
			case ANTI_ALIASING_MSAA_2X:
			case ANTI_ALIASING_MSAA_4X:
			case ANTI_ALIASING_MSAA_8X:
				if( r_antiAliasing.GetInteger() > 0 )
				{
					glEnable( GL_MULTISAMPLE );
				}
				break;

			default:
				glDisable( GL_MULTISAMPLE );
				break;
		}
	}

	if( r_usePBR.IsModified() ||
			r_useHDR.IsModified() ||
			r_useHalfLambertLighting.IsModified() ||
			r_pbrDebug.IsModified() )
	{
		bool needShaderReload = false;

		if( r_usePBR.GetBool() && r_useHalfLambertLighting.GetBool() )
		{
			r_useHalfLambertLighting.SetBool( false );

			needShaderReload = true;
		}

		needShaderReload |= r_useHDR.IsModified();
		needShaderReload |= r_pbrDebug.IsModified();

		r_usePBR.ClearModified();
		r_useHDR.ClearModified();
		r_useHalfLambertLighting.ClearModified();
		r_pbrDebug.ClearModified();

		renderProgManager.KillAllShaders();
		renderProgManager.LoadAllShaders();
	}

	// RB: turn off shadow mapping for OpenGL drivers that are too slow
	switch( glConfig.driverType )
	{
		case GLDRV_OPENGL_ES2:
		case GLDRV_OPENGL_ES3:
			//case GLDRV_OPENGL_MESA:
			r_useShadowMapping.SetInteger( 0 );
			break;

		default:
			break;
	}
	// RB end
}

/*
============================================================================

RENDER BACK END THREAD FUNCTIONS

============================================================================
*/

/*
=============
idRenderBackend::DrawFlickerBox
=============
*/
void idRenderBackend::DrawFlickerBox()
{
	if( !r_drawFlickerBox.GetBool() )
	{
		return;
	}
	if( tr.frameCount & 1 )
	{
		glClearColor( 1, 0, 0, 1 );
	}
	else
	{
		glClearColor( 0, 1, 0, 1 );
	}
	glScissor( 0, 0, 256, 256 );
	glClear( GL_COLOR_BUFFER_BIT );
}

/*
=============
idRenderBackend::SetBuffer
=============
*/
void idRenderBackend::SetBuffer( const void* data )
{
	// see which draw buffer we want to render the frame to

	const setBufferCommand_t* cmd = ( const setBufferCommand_t* )data;

	RENDERLOG_PRINTF( "---------- RB_SetBuffer ---------- to buffer # %d\n", cmd->buffer );

	GL_Scissor( 0, 0, tr.GetWidth(), tr.GetHeight() );

	// clear screen for debugging
	// automatically enable this with several other debug tools
	// that might leave unrendered portions of the screen
	if( r_clear.GetFloat() || idStr::Length( r_clear.GetString() ) != 1 || r_singleArea.GetBool() || r_showOverDraw.GetBool() )
	{
		float c[3];
		if( sscanf( r_clear.GetString(), "%f %f %f", &c[0], &c[1], &c[2] ) == 3 )
		{
			GL_Clear( true, false, false, 0, c[0], c[1], c[2], 1.0f, true );
		}
		else if( r_clear.GetInteger() == 2 )
		{
			GL_Clear( true, false, false, 0, 0.0f, 0.0f,  0.0f, 1.0f, true );
		}
		else if( r_showOverDraw.GetBool() )
		{
			GL_Clear( true, false, false, 0, 1.0f, 1.0f, 1.0f, 1.0f, true );
		}
		else
		{
			GL_Clear( true, false, false, 0, 0.4f, 0.0f, 0.25f, 1.0f, true );
		}
	}
}

/*
==============================================================================================

STENCIL SHADOW RENDERING

==============================================================================================
*/

/*
=====================
idRenderBackend::DrawStencilShadowPass
=====================
*/
extern idCVar r_useStencilShadowPreload;

void idRenderBackend::DrawStencilShadowPass( const drawSurf_t* drawSurf, const bool renderZPass )
{
	if( renderZPass )
	{
		// Z-pass
		glStencilOpSeparate( GL_FRONT, GL_KEEP, GL_KEEP, GL_INCR );
		glStencilOpSeparate( GL_BACK, GL_KEEP, GL_KEEP, GL_DECR );
	}
	else if( r_useStencilShadowPreload.GetBool() )
	{
		// preload + Z-pass
		glStencilOpSeparate( GL_FRONT, GL_KEEP, GL_DECR, GL_DECR );
		glStencilOpSeparate( GL_BACK, GL_KEEP, GL_INCR, GL_INCR );
	}
	else
	{
		// Z-fail (Carmack's Reverse)
		glStencilOpSeparate( GL_FRONT, GL_KEEP, GL_DECR, GL_KEEP );
		glStencilOpSeparate( GL_BACK, GL_KEEP, GL_INCR, GL_KEEP );
	}

	// get vertex buffer
	const vertCacheHandle_t vbHandle = drawSurf->shadowCache;
	idVertexBuffer* vertexBuffer;
	if( vertexCache.CacheIsStatic( vbHandle ) )
	{
		vertexBuffer = &vertexCache.staticData.vertexBuffer;
	}
	else
	{
		const uint64 frameNum = ( int )( vbHandle >> VERTCACHE_FRAME_SHIFT ) & VERTCACHE_FRAME_MASK;
		if( frameNum != ( ( vertexCache.currentFrame - 1 ) & VERTCACHE_FRAME_MASK ) )
		{
			idLib::Warning( "DrawStencilShadowPass, vertexBuffer == NULL" );
			return;
		}
		vertexBuffer = &vertexCache.frameData[ vertexCache.drawListNum ].vertexBuffer;
	}
	const int vertOffset = ( int )( vbHandle >> VERTCACHE_OFFSET_SHIFT ) & VERTCACHE_OFFSET_MASK;

	// get index buffer
	const vertCacheHandle_t ibHandle = drawSurf->indexCache;
	idIndexBuffer* indexBuffer;
	if( vertexCache.CacheIsStatic( ibHandle ) )
	{
		indexBuffer = &vertexCache.staticData.indexBuffer;
	}
	else
	{
		const uint64 frameNum = ( int )( ibHandle >> VERTCACHE_FRAME_SHIFT ) & VERTCACHE_FRAME_MASK;
		if( frameNum != ( ( vertexCache.currentFrame - 1 ) & VERTCACHE_FRAME_MASK ) )
		{
			idLib::Warning( "DrawStencilShadowPass, indexBuffer == NULL" );
			return;
		}
		indexBuffer = &vertexCache.frameData[ vertexCache.drawListNum ].indexBuffer;
	}
	const uint64 indexOffset = ( int )( ibHandle >> VERTCACHE_OFFSET_SHIFT ) & VERTCACHE_OFFSET_MASK;

	RENDERLOG_PRINTF( "Binding Buffers: %p %p\n", vertexBuffer, indexBuffer );

	// RB: 64 bit fixes, changed GLuint to GLintptr
	if( currentIndexBuffer != ( GLintptr )indexBuffer->GetAPIObject() || !r_useStateCaching.GetBool() )
	{
		glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, ( GLintptr )indexBuffer->GetAPIObject() );
		currentIndexBuffer = ( GLintptr )indexBuffer->GetAPIObject();
	}

	if( drawSurf->jointCache )
	{
		assert( renderProgManager.ShaderUsesJoints() );

		idUniformBuffer jointBuffer;
		if( !vertexCache.GetJointBuffer( drawSurf->jointCache, &jointBuffer ) )
		{
			idLib::Warning( "DrawStencilShadowPass, jointBuffer == NULL" );
			return;
		}
		assert( ( jointBuffer.GetOffset() & ( glConfig.uniformBufferOffsetAlignment - 1 ) ) == 0 );

		const GLintptr ubo = jointBuffer.GetAPIObject();
		glBindBufferRange( GL_UNIFORM_BUFFER, 0, ubo, jointBuffer.GetOffset(), jointBuffer.GetSize() );

		if( ( vertexLayout != LAYOUT_DRAW_SHADOW_VERT_SKINNED ) || ( currentVertexBuffer != ( GLintptr )vertexBuffer->GetAPIObject() ) || !r_useStateCaching.GetBool() )
		{
			glBindBuffer( GL_ARRAY_BUFFER, ( GLintptr )vertexBuffer->GetAPIObject() );
			currentVertexBuffer = ( GLintptr )vertexBuffer->GetAPIObject();

			glEnableVertexAttribArray( PC_ATTRIB_INDEX_VERTEX );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_NORMAL );
			glEnableVertexAttribArray( PC_ATTRIB_INDEX_COLOR );
			glEnableVertexAttribArray( PC_ATTRIB_INDEX_COLOR2 );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_ST );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_TANGENT );

#if defined(USE_GLES2) || defined(USE_GLES3)
			glVertexAttribPointer( PC_ATTRIB_INDEX_VERTEX, 4, GL_FLOAT, GL_FALSE, sizeof( idShadowVertSkinned ), ( void* )( vertOffset + SHADOWVERTSKINNED_XYZW_OFFSET ) );
			glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idShadowVertSkinned ), ( void* )( vertOffset + SHADOWVERTSKINNED_COLOR_OFFSET ) );
			glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR2, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idShadowVertSkinned ), ( void* )( vertOffset + SHADOWVERTSKINNED_COLOR2_OFFSET ) );
#else
			glVertexAttribPointer( PC_ATTRIB_INDEX_VERTEX, 4, GL_FLOAT, GL_FALSE, sizeof( idShadowVertSkinned ), ( void* )( SHADOWVERTSKINNED_XYZW_OFFSET ) );
			glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idShadowVertSkinned ), ( void* )( SHADOWVERTSKINNED_COLOR_OFFSET ) );
			glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR2, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idShadowVertSkinned ), ( void* )( SHADOWVERTSKINNED_COLOR2_OFFSET ) );
#endif

			vertexLayout = LAYOUT_DRAW_SHADOW_VERT_SKINNED;
		}

	}
	else
	{
		if( ( vertexLayout != LAYOUT_DRAW_SHADOW_VERT ) || ( currentVertexBuffer != ( GLintptr )vertexBuffer->GetAPIObject() ) || !r_useStateCaching.GetBool() )
		{
			glBindBuffer( GL_ARRAY_BUFFER, ( GLintptr )vertexBuffer->GetAPIObject() );
			currentVertexBuffer = ( GLintptr )vertexBuffer->GetAPIObject();

			glEnableVertexAttribArray( PC_ATTRIB_INDEX_VERTEX );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_NORMAL );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_COLOR );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_COLOR2 );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_ST );
			glDisableVertexAttribArray( PC_ATTRIB_INDEX_TANGENT );

#if defined(USE_GLES2) || defined(USE_GLES3)
			glVertexAttribPointer( PC_ATTRIB_INDEX_VERTEX, 4, GL_FLOAT, GL_FALSE, sizeof( idShadowVert ), ( void* )( vertOffset + SHADOWVERT_XYZW_OFFSET ) );
#else
			glVertexAttribPointer( PC_ATTRIB_INDEX_VERTEX, 4, GL_FLOAT, GL_FALSE, sizeof( idShadowVert ), ( void* )( SHADOWVERT_XYZW_OFFSET ) );
#endif

			vertexLayout = LAYOUT_DRAW_SHADOW_VERT;
		}
	}
	// RB end

	renderProgManager.CommitUniforms( glStateBits );

	if( drawSurf->jointCache )
	{
#if defined(USE_GLES3) //defined(USE_GLES2)
		glDrawElements( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset );
#else
		glDrawElementsBaseVertex( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset, vertOffset / sizeof( idShadowVertSkinned ) );
#endif
	}
	else
	{
#if defined(USE_GLES3)
		glDrawElements( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset );
#else
		glDrawElementsBaseVertex( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset, vertOffset / sizeof( idShadowVert ) );
#endif
	}

	// RB: added stats
	pc.c_shadowElements++;
	pc.c_shadowIndexes += drawSurf->numIndexes;
	// RB end

	if( !renderZPass && r_useStencilShadowPreload.GetBool() )
	{
		// render again with Z-pass
		glStencilOpSeparate( GL_FRONT, GL_KEEP, GL_KEEP, GL_INCR );
		glStencilOpSeparate( GL_BACK, GL_KEEP, GL_KEEP, GL_DECR );

		if( drawSurf->jointCache )
		{
#if defined(USE_GLES3)
			glDrawElements( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset );
#else
			glDrawElementsBaseVertex( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset, vertOffset / sizeof( idShadowVertSkinned ) );
#endif
		}
		else
		{
#if defined(USE_GLES3)
			glDrawElements( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset );
#else
			glDrawElementsBaseVertex( GL_TRIANGLES, r_singleTriangle.GetBool() ? 3 : drawSurf->numIndexes, GL_INDEX_TYPE, ( triIndex_t* )indexOffset, vertOffset / sizeof( idShadowVert ) );
#endif
		}

		// RB: added stats
		pc.c_shadowElements++;
		pc.c_shadowIndexes += drawSurf->numIndexes;
		// RB end
	}
}


/*
=============
idRenderBackend::idRenderBackend
=============
*/
idRenderBackend::idRenderBackend()
{
	memset( glcontext.tmu, 0, sizeof( glcontext.tmu ) );
	memset( glcontext.stencilOperations, 0, sizeof( glcontext.stencilOperations ) );
}

/*
=============
idRenderBackend::~idRenderBackend
=============
*/
idRenderBackend::~idRenderBackend()
{

}

/*
====================
R_MakeStereoRenderImage
====================
*/
static void R_MakeStereoRenderImage( idImage* image )
{
	idImageOpts	opts;
	opts.width = renderSystem->GetWidth();
	opts.height = renderSystem->GetHeight();
	opts.numLevels = 1;
	opts.format = FMT_RGBA8;
	image->AllocImage( opts, TF_LINEAR, TR_CLAMP );
}

/*
====================
idRenderBackend::StereoRenderExecuteBackEndCommands

Renders the draw list twice, with slight modifications for left eye / right eye
====================
*/
void idRenderBackend::StereoRenderExecuteBackEndCommands( const emptyCommand_t* const allCmds )
{
	uint64 backEndStartTime = Sys_Microseconds();

	// If we are in a monoscopic context, this draws to the only buffer, and is
	// the same as GL_BACK.  In a quad-buffer stereo context, this is necessary
	// to prevent GL from forcing the rendering to go to both BACK_LEFT and
	// BACK_RIGHT at a performance penalty.
	// To allow stereo deghost processing, the views have to be copied to separate
	// textures anyway, so there isn't any benefit to rendering to BACK_RIGHT for
	// that eye.
	glDrawBuffer( GL_BACK_LEFT );

	// create the stereoRenderImage if we haven't already
	static idImage* stereoRenderImages[2];
	for( int i = 0; i < 2; i++ )
	{
		if( stereoRenderImages[i] == NULL )
		{
			stereoRenderImages[i] = globalImages->ImageFromFunction( va( "_stereoRender%i", i ), R_MakeStereoRenderImage );
		}

		// resize the stereo render image if the main window has changed size
		if( stereoRenderImages[i]->GetUploadWidth() != renderSystem->GetWidth() ||
				stereoRenderImages[i]->GetUploadHeight() != renderSystem->GetHeight() )
		{
			stereoRenderImages[i]->Resize( renderSystem->GetWidth(), renderSystem->GetHeight() );
		}
	}

	// In stereoRender mode, the front end has generated two RC_DRAW_VIEW commands
	// with slightly different origins for each eye.

	// TODO: only do the copy after the final view has been rendered, not mirror subviews?

	// Render the 3D draw views from the screen origin so all the screen relative
	// texture mapping works properly, then copy the portion we are going to use
	// off to a texture.
	bool foundEye[2] = { false, false };

	for( int stereoEye = 1; stereoEye >= -1; stereoEye -= 2 )
	{
		// set up the target texture we will draw to
		const int targetEye = ( stereoEye == 1 ) ? 1 : 0;

		// Set the back end into a known default state to fix any stale render state issues
		GL_SetDefaultState();

		renderProgManager.Unbind();
		renderProgManager.ZeroUniforms();

		for( const emptyCommand_t* cmds = allCmds; cmds != NULL; cmds = ( const emptyCommand_t* )cmds->next )
		{
			switch( cmds->commandId )
			{
				case RC_NOP:
					break;
				case RC_DRAW_VIEW_GUI:
				case RC_DRAW_VIEW_3D:
				{
					const drawSurfsCommand_t* const dsc = ( const drawSurfsCommand_t* )cmds;
					const viewDef_t&			eyeViewDef = *dsc->viewDef;

					if( eyeViewDef.renderView.viewEyeBuffer && eyeViewDef.renderView.viewEyeBuffer != stereoEye )
					{
						// this is the render view for the other eye
						continue;
					}

					foundEye[ targetEye ] = true;
					DrawView( dsc, stereoEye );
					if( cmds->commandId == RC_DRAW_VIEW_GUI )
					{
					}
				}
				break;
				case RC_SET_BUFFER:
					SetBuffer( cmds );
					break;
				case RC_COPY_RENDER:
					CopyRender( cmds );
					break;
				case RC_POST_PROCESS:
				{
					postProcessCommand_t* cmd = ( postProcessCommand_t* )cmds;
					if( cmd->viewDef->renderView.viewEyeBuffer != stereoEye )
					{
						break;
					}
					PostProcess( cmds );
				}
				break;
				default:
					common->Error( "RB_ExecuteBackEndCommands: bad commandId" );
					break;
			}
		}

		// copy to the target
		stereoRenderImages[ targetEye ]->CopyFramebuffer( 0, 0, renderSystem->GetWidth(), renderSystem->GetHeight() );
	}

	// perform the final compositing / warping / deghosting to the actual framebuffer(s)
	assert( foundEye[0] && foundEye[1] );

	GL_SetDefaultState();

	RB_SetMVP( renderMatrix_identity );

	// If we are in quad-buffer pixel format but testing another 3D mode,
	// make sure we draw to both eyes.  This is likely to be sub-optimal
	// performance on most cards and drivers, but it is better than getting
	// a confusing, half-ghosted view.
	if( renderSystem->GetStereo3DMode() != STEREO3D_QUAD_BUFFER )
	{
		glDrawBuffer( GL_BACK );
	}

	GL_State( GLS_DEPTHFUNC_ALWAYS | GLS_CULL_TWOSIDED );

	// We just want to do a quad pass - so make sure we disable any texgen and
	// set the texture matrix to the identity so we don't get anomalies from
	// any stale uniform data being present from a previous draw call
	const float texS[4] = { 1.0f, 0.0f, 0.0f, 0.0f };
	const float texT[4] = { 0.0f, 1.0f, 0.0f, 0.0f };
	renderProgManager.SetRenderParm( RENDERPARM_TEXTUREMATRIX_S, texS );
	renderProgManager.SetRenderParm( RENDERPARM_TEXTUREMATRIX_T, texT );

	// disable any texgen
	const float texGenEnabled[4] = { 0.0f, 0.0f, 0.0f, 0.0f };
	renderProgManager.SetRenderParm( RENDERPARM_TEXGEN_0_ENABLED, texGenEnabled );

	renderProgManager.BindShader_Texture();
	GL_Color( 1, 1, 1, 1 );

	switch( renderSystem->GetStereo3DMode() )
	{
		case STEREO3D_QUAD_BUFFER:
			glDrawBuffer( GL_BACK_RIGHT );
			GL_SelectTexture( 0 );
			stereoRenderImages[1]->Bind();
			GL_SelectTexture( 1 );
			stereoRenderImages[0]->Bind();
			DrawElementsWithCounters( &unitSquareSurface );

			glDrawBuffer( GL_BACK_LEFT );
			GL_SelectTexture( 1 );
			stereoRenderImages[1]->Bind();
			GL_SelectTexture( 0 );
			stereoRenderImages[0]->Bind();
			DrawElementsWithCounters( &unitSquareSurface );
			break;

		case STEREO3D_HDMI_720:
			// HDMI 720P 3D
			GL_SelectTexture( 0 );
			stereoRenderImages[1]->Bind();
			GL_SelectTexture( 1 );
			stereoRenderImages[0]->Bind();
			GL_ViewportAndScissor( 0, 0, 1280, 720 );
			DrawElementsWithCounters( &unitSquareSurface );

			GL_SelectTexture( 0 );
			stereoRenderImages[0]->Bind();
			GL_SelectTexture( 1 );
			stereoRenderImages[1]->Bind();
			GL_ViewportAndScissor( 0, 750, 1280, 720 );
			DrawElementsWithCounters( &unitSquareSurface );

			// force the HDMI 720P 3D guard band to a constant color
			glScissor( 0, 720, 1280, 30 );
			glClear( GL_COLOR_BUFFER_BIT );
			break;

		default:
		case STEREO3D_SIDE_BY_SIDE:
			if( stereoRender_warp.GetBool() )
			{
				// this is the Rift warp
				// renderSystem->GetWidth() / GetHeight() have returned equal values (640 for initial Rift)
				// and we are going to warp them onto a symetric square region of each half of the screen

				renderProgManager.BindShader_StereoWarp();

				// clear the entire screen to black
				// we could be smart and only clear the areas we aren't going to draw on, but
				// clears are fast...
				glScissor( 0, 0, glConfig.nativeScreenWidth, glConfig.nativeScreenHeight );
				glClearColor( 0, 0, 0, 0 );
				glClear( GL_COLOR_BUFFER_BIT );

				// the size of the box that will get the warped pixels
				// With the 7" displays, this will be less than half the screen width
				const int pixelDimensions = ( glConfig.nativeScreenWidth >> 1 ) * stereoRender_warpTargetFraction.GetFloat();

				// Always scissor to the half-screen boundary, but the viewports
				// might cross that boundary if the lenses can be adjusted closer
				// together.
				glViewport( ( glConfig.nativeScreenWidth >> 1 ) - pixelDimensions,
							( glConfig.nativeScreenHeight >> 1 ) - ( pixelDimensions >> 1 ),
							pixelDimensions, pixelDimensions );
				glScissor( 0, 0, glConfig.nativeScreenWidth >> 1, glConfig.nativeScreenHeight );

				idVec4	color( stereoRender_warpCenterX.GetFloat(), stereoRender_warpCenterY.GetFloat(), stereoRender_warpParmZ.GetFloat(), stereoRender_warpParmW.GetFloat() );
				// don't use GL_Color(), because we don't want to clamp
				renderProgManager.SetRenderParm( RENDERPARM_COLOR, color.ToFloatPtr() );

				GL_SelectTexture( 0 );
				stereoRenderImages[0]->Bind();
				glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER );
				glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER );
				DrawElementsWithCounters( &unitSquareSurface );

				idVec4	color2( stereoRender_warpCenterX.GetFloat(), stereoRender_warpCenterY.GetFloat(), stereoRender_warpParmZ.GetFloat(), stereoRender_warpParmW.GetFloat() );
				// don't use GL_Color(), because we don't want to clamp
				renderProgManager.SetRenderParm( RENDERPARM_COLOR, color2.ToFloatPtr() );

				glViewport( ( glConfig.nativeScreenWidth >> 1 ),
							( glConfig.nativeScreenHeight >> 1 ) - ( pixelDimensions >> 1 ),
							pixelDimensions, pixelDimensions );
				glScissor( glConfig.nativeScreenWidth >> 1, 0, glConfig.nativeScreenWidth >> 1, glConfig.nativeScreenHeight );

				GL_SelectTexture( 0 );
				stereoRenderImages[1]->Bind();
				glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER );
				glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER );
				DrawElementsWithCounters( &unitSquareSurface );
				break;
			}

		// a non-warped side-by-side-uncompressed (dual input cable) is rendered
		// just like STEREO3D_SIDE_BY_SIDE_COMPRESSED, so fall through.
		case STEREO3D_SIDE_BY_SIDE_COMPRESSED:
			GL_SelectTexture( 0 );
			stereoRenderImages[0]->Bind();
			GL_SelectTexture( 1 );
			stereoRenderImages[1]->Bind();
			GL_ViewportAndScissor( 0, 0, renderSystem->GetWidth(), renderSystem->GetHeight() );
			DrawElementsWithCounters( &unitSquareSurface );

			GL_SelectTexture( 0 );
			stereoRenderImages[1]->Bind();
			GL_SelectTexture( 1 );
			stereoRenderImages[0]->Bind();
			GL_ViewportAndScissor( renderSystem->GetWidth(), 0, renderSystem->GetWidth(), renderSystem->GetHeight() );
			DrawElementsWithCounters( &unitSquareSurface );
			break;

		case STEREO3D_TOP_AND_BOTTOM_COMPRESSED:
			GL_SelectTexture( 1 );
			stereoRenderImages[0]->Bind();
			GL_SelectTexture( 0 );
			stereoRenderImages[1]->Bind();
			GL_ViewportAndScissor( 0, 0, renderSystem->GetWidth(), renderSystem->GetHeight() );
			DrawElementsWithCounters( &unitSquareSurface );

			GL_SelectTexture( 1 );
			stereoRenderImages[1]->Bind();
			GL_SelectTexture( 0 );
			stereoRenderImages[0]->Bind();
			GL_ViewportAndScissor( 0, renderSystem->GetHeight(), renderSystem->GetWidth(), renderSystem->GetHeight() );
			DrawElementsWithCounters( &unitSquareSurface );
			break;

		case STEREO3D_INTERLACED:
			// every other scanline
			GL_SelectTexture( 0 );
			stereoRenderImages[0]->Bind();
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );

			GL_SelectTexture( 1 );
			stereoRenderImages[1]->Bind();
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );

			GL_ViewportAndScissor( 0, 0, renderSystem->GetWidth(), renderSystem->GetHeight() * 2 );
			renderProgManager.BindShader_StereoInterlace();
			DrawElementsWithCounters( &unitSquareSurface );

			GL_SelectTexture( 0 );
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

			GL_SelectTexture( 1 );
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
			glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

			break;
	}

	// debug tool
	DrawFlickerBox();

	// make sure the drawing is actually started
	glFlush();

	// we may choose to sync to the swapbuffers before the next frame

	// stop rendering on this thread
	uint64 backEndFinishTime = Sys_Microseconds();
	pc.totalMicroSec = backEndFinishTime - backEndStartTime;
}

/*
==============================================================================================

IMGUI RENDERING

==============================================================================================
*/
#include "../../libs/imgui/imgui.h"

int          g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
int          g_AttribLocationTex = 0, g_AttribLocationProjMtx = 0;
int          g_AttribLocationPosition = 0, g_AttribLocationUV = 0, g_AttribLocationColor = 0;
unsigned int g_VboHandle = 0, g_VaoHandle = 0, g_ElementsHandle = 0;

void idRenderBackend::ImGui_Init()
{
#if 1
	const GLchar* vertex_shader =
		"#version 330\n"
		"uniform mat4 ProjMtx;\n"
		"in vec2 Position;\n"
		"in vec2 UV;\n"
		"in vec4 Color;\n"
		"out vec2 Frag_UV;\n"
		"out vec4 Frag_Color;\n"
		"void main()\n"
		"{\n"
		"	Frag_UV = UV;\n"
		"	Frag_Color = Color;\n"
		"	gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
		"}\n";

	const GLchar* fragment_shader =
		"#version 330\n"
		"uniform sampler2D Texture;\n"
		"in vec2 Frag_UV;\n"
		"in vec4 Frag_Color;\n"
		"out vec4 Out_Color;\n"
		"void main()\n"
		"{\n"
		"	Out_Color = Frag_Color * texture( Texture, Frag_UV.st);\n"
		"}\n";

	g_ShaderHandle = glCreateProgram();
	g_VertHandle = glCreateShader( GL_VERTEX_SHADER );
	g_FragHandle = glCreateShader( GL_FRAGMENT_SHADER );
	glShaderSource( g_VertHandle, 1, &vertex_shader, 0 );
	glShaderSource( g_FragHandle, 1, &fragment_shader, 0 );
	glCompileShader( g_VertHandle );
	glCompileShader( g_FragHandle );
	glAttachShader( g_ShaderHandle, g_VertHandle );
	glAttachShader( g_ShaderHandle, g_FragHandle );
	glLinkProgram( g_ShaderHandle );

	g_AttribLocationTex = glGetUniformLocation( g_ShaderHandle, "Texture" );
	g_AttribLocationProjMtx = glGetUniformLocation( g_ShaderHandle, "ProjMtx" );
	g_AttribLocationPosition = glGetAttribLocation( g_ShaderHandle, "Position" );
	g_AttribLocationUV = glGetAttribLocation( g_ShaderHandle, "UV" );
	g_AttribLocationColor = glGetAttribLocation( g_ShaderHandle, "Color" );

	glGenBuffers( 1, &g_VboHandle );
	glGenBuffers( 1, &g_ElementsHandle );

	glGenVertexArrays( 1, &g_VaoHandle );
	glBindVertexArray( g_VaoHandle );
	glBindBuffer( GL_ARRAY_BUFFER, g_VboHandle );
	glEnableVertexAttribArray( g_AttribLocationPosition );
	glEnableVertexAttribArray( g_AttribLocationUV );
	glEnableVertexAttribArray( g_AttribLocationColor );

#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
	glVertexAttribPointer( g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof( ImDrawVert ), ( GLvoid* )OFFSETOF( ImDrawVert, pos ) );
	glVertexAttribPointer( g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof( ImDrawVert ), ( GLvoid* )OFFSETOF( ImDrawVert, uv ) );
	glVertexAttribPointer( g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( ImDrawVert ), ( GLvoid* )OFFSETOF( ImDrawVert, col ) );
#undef OFFSETOF
	glBindVertexArray( 0 );
	glBindBuffer( GL_ARRAY_BUFFER, 0 );
#endif
}

void idRenderBackend::ImGui_Shutdown()
{
	if( g_VaoHandle )
	{
		glDeleteVertexArrays( 1, &g_VaoHandle );
	}
	if( g_VboHandle )
	{
		glDeleteBuffers( 1, &g_VboHandle );
	}
	if( g_ElementsHandle )
	{
		glDeleteBuffers( 1, &g_ElementsHandle );
	}
	g_VaoHandle = g_VboHandle = g_ElementsHandle = 0;

	glDetachShader( g_ShaderHandle, g_VertHandle );
	glDeleteShader( g_VertHandle );
	g_VertHandle = 0;

	glDetachShader( g_ShaderHandle, g_FragHandle );
	glDeleteShader( g_FragHandle );
	g_FragHandle = 0;

	glDeleteProgram( g_ShaderHandle );
	g_ShaderHandle = 0;

	//ImGui::GetIO().Fonts->TexID = 0;
}

// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
// If text or lines are blurry when integrating ImGui in your engine:
// - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
void idRenderBackend::ImGui_RenderDrawLists( ImDrawData* draw_data )
{
	// Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
	GLint last_program, last_texture, polygon_mode[2];
	glGetIntegerv( GL_CURRENT_PROGRAM, &last_program );
	glGetIntegerv( GL_TEXTURE_BINDING_2D, &last_texture );
	glGetIntegerv( GL_POLYGON_MODE, polygon_mode );
	glEnable( GL_BLEND );
	glBlendEquation( GL_FUNC_ADD );
	glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
	glDisable( GL_CULL_FACE );
	glDisable( GL_DEPTH_TEST );
	glEnable( GL_SCISSOR_TEST );
	glActiveTexture( GL_TEXTURE0 );

	glPolygonMode( GL_FRONT_AND_BACK, GL_FILL );

	// Setup orthographic projection matrix
	const float width = ImGui::GetIO().DisplaySize.x;
	const float height = ImGui::GetIO().DisplaySize.y;
	const float ortho_projection[4][4] =
	{
		{ 2.0f / width,	0.0f,			0.0f,		0.0f },
		{ 0.0f,			2.0f / -height,	0.0f,		0.0f },
		{ 0.0f,			0.0f,			-1.0f,		0.0f },
		{ -1.0f,		1.0f,			0.0f,		1.0f },
	};

	glUseProgram( g_ShaderHandle );
	glUniform1i( g_AttribLocationTex, 0 );
	glUniformMatrix4fv( g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0] );
	glBindVertexArray( g_VaoHandle );

#if 0
	glDisableVertexAttribArray( PC_ATTRIB_INDEX_VERTEX );
	glDisableVertexAttribArray( PC_ATTRIB_INDEX_NORMAL );
	glDisableVertexAttribArray( PC_ATTRIB_INDEX_COLOR );
	glDisableVertexAttribArray( PC_ATTRIB_INDEX_COLOR2 );
	glDisableVertexAttribArray( PC_ATTRIB_INDEX_ST );
	glDisableVertexAttribArray( PC_ATTRIB_INDEX_TANGENT );

	//glVertexAttribPointer( PC_ATTRIB_INDEX_VERTEX, 4, GL_FLOAT, GL_FALSE, sizeof( idShadowVertSkinned ), ( void* )( SHADOWVERTSKINNED_XYZW_OFFSET ) );
	//glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idShadowVertSkinned ), ( void* )( SHADOWVERTSKINNED_COLOR_OFFSET ) );
	//glVertexAttribPointer( PC_ATTRIB_INDEX_COLOR2, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( idShadowVertSkinned ), ( void* )( SHADOWVERTSKINNED_COLOR2_OFFSET ) );

	glEnableVertexAttribArray( g_AttribLocationPosition );
	glEnableVertexAttribArray( g_AttribLocationUV );
	glEnableVertexAttribArray( g_AttribLocationColor );

#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
	glVertexAttribPointer( g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof( ImDrawVert ), ( GLvoid* )OFFSETOF( ImDrawVert, pos ) );
	glVertexAttribPointer( g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof( ImDrawVert ), ( GLvoid* )OFFSETOF( ImDrawVert, uv ) );
	glVertexAttribPointer( g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof( ImDrawVert ), ( GLvoid* )OFFSETOF( ImDrawVert, col ) );
#undef OFFSETOF

#endif
	tr.backend.vertexLayout = LAYOUT_DRAW_IMGUI_VERT;

	for( int n = 0; n < draw_data->CmdListsCount; n++ )
	{
		const ImDrawList* cmd_list = draw_data->CmdLists[n];
		const ImDrawIdx* idx_buffer_offset = 0;

		glBindBuffer( GL_ARRAY_BUFFER, g_VboHandle );
		glBufferData( GL_ARRAY_BUFFER, ( GLsizeiptr )cmd_list->VtxBuffer.size() * sizeof( ImDrawVert ), ( GLvoid* )&cmd_list->VtxBuffer.front(), GL_STREAM_DRAW );

		glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, g_ElementsHandle );
		glBufferData( GL_ELEMENT_ARRAY_BUFFER, ( GLsizeiptr )cmd_list->IdxBuffer.size() * sizeof( ImDrawIdx ), ( GLvoid* )&cmd_list->IdxBuffer.front(), GL_STREAM_DRAW );

		for( const ImDrawCmd* pcmd = cmd_list->CmdBuffer.begin(); pcmd != cmd_list->CmdBuffer.end(); pcmd++ )
		{
			if( pcmd->UserCallback )
			{
				pcmd->UserCallback( cmd_list, pcmd );
			}
			else
			{
				glBindTexture( GL_TEXTURE_2D, ( GLuint )( intptr_t )pcmd->TextureId );
				glScissor( ( int )pcmd->ClipRect.x, ( int )( height - pcmd->ClipRect.w ), ( int )( pcmd->ClipRect.z - pcmd->ClipRect.x ), ( int )( pcmd->ClipRect.w - pcmd->ClipRect.y ) );
				glDrawElements( GL_TRIANGLES, ( GLsizei )pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer_offset );
			}
			idx_buffer_offset += pcmd->ElemCount;
		}
	}

	// Restore modified state
	//glPolygonMode( polygon_mode[0], polygon_mode[1] );
	glBindVertexArray( glConfig.global_vao );

	glBindBuffer( GL_ARRAY_BUFFER, 0 );
	glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, 0 );
	glUseProgram( last_program );
	glDisable( GL_SCISSOR_TEST );
	glBindTexture( GL_TEXTURE_2D, last_texture );

	renderProgManager.Unbind();
}