- add gl_dither for toggling dithered output on and off

# Conflicts:
#	src/gl/renderer/gl_stereo3d.cpp
#	wadsrc/static/menudef.txt

# Conflicts:
#	src/gl/renderer/gl_postprocess.cpp
#	src/gl/stereo3d/gl_interleaved3d.cpp
#	src/hwrenderer/postprocessing/hw_presentshader.h

src/gl/renderer/gl_postprocess.cpp

@@ -157,6 +157,8 @@ EXTERN_CVAR(Float, vid_contrast)
 EXTERN_CVAR(Float, vid_saturation)
 EXTERN_CVAR(Int, gl_satformula)
 
+CVAR(Bool, gl_dither, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG | CVAR_NOINITCALL)
+
 void FGLRenderer::RenderScreenQuad()
 {
 	mVBO->BindVBO();
@@ -900,6 +902,11 @@ void FGLRenderer::DrawPresentTexture(const GL_IRECT &box, bool applyGamma)
 		// It probably will eventually in desktop mode too, but the DWM doesn't seem to support that.
 		invgamma *= 2.2f;
 		mPresentShader->InvGamma.Set(invgamma);
+		mPresentShader->ColorScale.Set(static_cast<float>(gl_dither ? 1023.0f : 0.0f));
+	}
+	else
+	{
+		mPresentShader->ColorScale.Set(static_cast<float>(gl_dither ? 255.0f : 0.0f));
 	}
 	mPresentShader->Scale.Set(mScreenViewport.width / (float)mBuffers->GetWidth(), mScreenViewport.height / (float)mBuffers->GetHeight());
 	RenderScreenQuad();

src/gl/shaders/gl_presentshader.cpp

@@ -49,6 +49,7 @@ void FPresentShaderBase::Init(const char * vtx_shader_name, const char * program
 	Saturation.Init(mShader, "Saturation");
 	GrayFormula.Init(mShader, "GrayFormula");
 	Scale.Init(mShader, "UVScale");
+	ColorScale.Init(mShader, "ColorScale");
 }
 
 void FPresentShader::Bind()

src/gl/shaders/gl_presentshader.h

@@ -15,6 +15,7 @@ public:
 	FBufferedUniform1f Saturation;
 	FBufferedUniform1i GrayFormula;
 	FBufferedUniform2f Scale;
+	FBufferedUniform1f ColorScale;
 
 protected:
 	virtual void Init(const char * vtx_shader_name, const char * program_name);

src/gl/stereo3d/gl_interleaved3d.cpp

@@ -48,6 +48,7 @@ EXTERN_CVAR(Int, gl_satformula)
 EXTERN_CVAR(Bool, fullscreen)
 EXTERN_CVAR(Int, win_x) // screen pixel position of left of display window
 EXTERN_CVAR(Int, win_y) // screen pixel position of top of display window
+EXTERN_CVAR(Bool, gl_dither)
 
 namespace s3d {
 
@@ -112,6 +113,7 @@ static void prepareInterleavedPresent(FPresentStereoShaderBase& shader)
 		shader.Saturation.Set(clamp<float>(vid_saturation, -15.0f, 15.0f));
 		shader.GrayFormula.Set(static_cast<int>(gl_satformula));
 	}
+	shader.ColorScale.Set(static_cast<float>(gl_dither ? 255.0f : 0.0f));
 	shader.Scale.Set(
 		GLRenderer->mScreenViewport.width / (float)GLRenderer->mBuffers->GetWidth(),
 		GLRenderer->mScreenViewport.height / (float)GLRenderer->mBuffers->GetHeight());

wadsrc/static/language.enu

@@ -2769,6 +2769,7 @@ GLPREFMNU_LENS					= "Lens distortion effect";
 GLPREFMNU_SSAO					= "Ambient occlusion quality";
 GLPREFMNU_SSAO_PORTALS			= "Portals with AO";
 GLPREFMNU_FXAA					= "FXAA Quality";
+GLPREFMNU_DITHER				= "Dither output";
 GLPREFMNU_PALTONEMAPORDER		= "Tonemap Palette Order";
 GLPREFMNU_PALTONEMAPPOWER		= "Tonemap Palette Exponent";
 GLPREFMNU_SWLMBANDED			= "Banded SW Lightmode";

wadsrc/static/menudef.txt

@@ -2548,6 +2548,7 @@ OptionMenu "PostProcessMenu" protected
 	Option "$GLPREFMNU_SSAO",		 			gl_ssao,						"SSAOModes"
 	Slider "$GLPREFMNU_SSAO_PORTALS",			gl_ssao_portals,				0.0, 4.0, 1.0, 0
 	Option "$GLPREFMNU_FXAA",		 			gl_fxaa,						"FXAAQuality"
+	Option "$GLPREFMNU_DITHER",		 			gl_dither,						"OnOff"
 	Option "$GLPREFMNU_TONEMAP", 				gl_tonemap,						"TonemapModes"
 	StaticText " "
 	Slider "$GLPREFMNU_PALTONEMAPPOWER",		gl_paltonemap_powtable,			0.2, 3.0, 0.1, 1

wadsrc/static/shaders/glsl/present.fp

@@ -9,6 +9,7 @@ uniform float Brightness;
 uniform float Saturation;
 uniform int GrayFormula;
 uniform sampler2D DitherTexture;
+uniform float ColorScale;
 
 vec4 ApplyGamma(vec4 c)
 {
@@ -23,14 +24,16 @@ vec4 ApplyGamma(vec4 c)
 	return vec4(val, c.a);
 }
 
-vec4 Dither(vec4 c, float colorscale)
+vec4 Dither(vec4 c)
 {
+	if (ColorScale == 0.0)
+		return c;
 	vec2 texSize = vec2(textureSize(DitherTexture, 0));
 	float threshold = texture(DitherTexture, gl_FragCoord.xy / texSize).r;
-	return vec4(floor(c.rgb * colorscale + threshold) / colorscale, c.a);
+	return vec4(floor(c.rgb * ColorScale + threshold) / ColorScale, c.a);
 }
 
 void main()
 {
-	FragColor = Dither(ApplyGamma(texture(InputTexture, TexCoord)), 255.0);
+	FragColor = Dither(ApplyGamma(texture(InputTexture, TexCoord)));
 }