diff --git a/src/gl/renderer/gl_renderer.cpp b/src/gl/renderer/gl_renderer.cpp
index 2f17ff99be..ae2ba21250 100644
--- a/src/gl/renderer/gl_renderer.cpp
+++ b/src/gl/renderer/gl_renderer.cpp
@@ -383,7 +383,7 @@ void FGLRenderer::DrawTexture(FTexture *img, DCanvas::DrawParms &parms)
 	glScissor(parms.lclip, btm - parms.dclip + space, parms.rclip - parms.lclip, parms.dclip - parms.uclip);
 	
 	gl_RenderState.SetColor(color);
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.Apply();
 
 	FFlatVertex *ptr = GLRenderer->mVBO->GetBuffer();
@@ -409,8 +409,6 @@ void FGLRenderer::DrawTexture(FTexture *img, DCanvas::DrawParms &parms)
 		GLRenderer->mVBO->RenderCurrent(ptr, GL_TRIANGLE_STRIP);
 	}
 
-	gl_RenderState.EnableAlphaTest(true);
-	
 	glScissor(0, 0, screen->GetWidth(), screen->GetHeight());
 	glDisable(GL_SCISSOR_TEST);
 	gl_RenderState.SetTextureMode(TM_MODULATE);
diff --git a/src/gl/renderer/gl_renderstate.cpp b/src/gl/renderer/gl_renderstate.cpp
index 27e4465c1e..9171708720 100644
--- a/src/gl/renderer/gl_renderstate.cpp
+++ b/src/gl/renderer/gl_renderstate.cpp
@@ -75,8 +75,6 @@ void FRenderState::Reset()
 	mSrcBlend = GL_SRC_ALPHA;
 	mDstBlend = GL_ONE_MINUS_SRC_ALPHA;
 	glSrcBlend = glDstBlend = -1;
-	glAlphaFunc = -1;
-	mAlphaFunc = GL_GEQUAL;
 	mAlphaThreshold = 0.5f;
 	mBlendEquation = GL_FUNC_ADD;
 	mObjectColor = 0xffffffff;
@@ -151,6 +149,7 @@ bool FRenderState::ApplyShader()
 	activeShader->muInterpolationFactor.Set(mInterpolationFactor);
 	activeShader->muClipHeightTop.Set(mClipHeightTop);
 	activeShader->muClipHeightBottom.Set(mClipHeightBottom);
+	activeShader->muAlphaThreshold.Set(mAlphaThreshold);
 
 	if (mGlowEnabled)
 	{
@@ -269,18 +268,6 @@ void FRenderState::Apply()
 			glDstBlend = mDstBlend;
 			glBlendFunc(mSrcBlend, mDstBlend);
 		}
-		if (mAlphaFunc != glAlphaFunc || mAlphaThreshold != glAlphaThreshold)
-		{
-			glAlphaFunc = mAlphaFunc;
-			glAlphaThreshold = mAlphaThreshold;
-			::glAlphaFunc(mAlphaFunc, mAlphaThreshold);
-		}
-		if (mAlphaTest != glAlphaTest)
-		{
-			glAlphaTest = mAlphaTest;
-			if (mAlphaTest) glEnable(GL_ALPHA_TEST);
-			else glDisable(GL_ALPHA_TEST);
-		}
 		if (mBlendEquation != glBlendEquation)
 		{
 			glBlendEquation = mBlendEquation;
diff --git a/src/gl/renderer/gl_renderstate.h b/src/gl/renderer/gl_renderstate.h
index d650e49b4d..d8168bca57 100644
--- a/src/gl/renderer/gl_renderstate.h
+++ b/src/gl/renderer/gl_renderstate.h
@@ -53,7 +53,6 @@ class FRenderState
 	int mNumLights[4];
 	float *mLightData;
 	int mSrcBlend, mDstBlend;
-	int mAlphaFunc;
 	float mAlphaThreshold;
 	bool mAlphaTest;
 	int mBlendEquation;
@@ -76,7 +75,6 @@ class FRenderState
 	int mColormapState;
 
 	int glSrcBlend, glDstBlend;
-	int glAlphaFunc;
 	float glAlphaThreshold;
 	bool glAlphaTest;
 	int glBlendEquation;
@@ -281,28 +279,8 @@ public:
 
 	void AlphaFunc(int func, float thresh)
 	{
-		if (!gl_direct_state_change)
-		{
-			mAlphaFunc = func;
-			mAlphaThreshold = thresh;
-		}
-		else
-		{
-			::glAlphaFunc(func, thresh);
-		}
-	}
-
-	void EnableAlphaTest(bool on)
-	{
-		if (!gl_direct_state_change)
-		{
-			mAlphaTest = on;
-		}
-		else
-		{
-			if (on) glEnable(GL_ALPHA_TEST);
-			else glDisable(GL_ALPHA_TEST);
-		}
+		if (func == GL_GREATER) mAlphaThreshold = thresh;
+		else mAlphaThreshold = thresh - 0.001f;
 	}
 
 	void BlendEquation(int eq)
diff --git a/src/gl/scene/gl_decal.cpp b/src/gl/scene/gl_decal.cpp
index e6d5c144f2..98101c987a 100644
--- a/src/gl/scene/gl_decal.cpp
+++ b/src/gl/scene/gl_decal.cpp
@@ -333,7 +333,7 @@ void GLWall::DrawDecal(DBaseDecal *decal)
 
 
 	// If srcalpha is one it looks better with a higher alpha threshold
-	if (decal->RenderStyle.SrcAlpha == STYLEALPHA_One) gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_threshold);
+	if (decal->RenderStyle.SrcAlpha == STYLEALPHA_One) gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_sprite_threshold);
 	else gl_RenderState.AlphaFunc(GL_GREATER, 0.f);
 
 	gl_RenderState.Apply();
diff --git a/src/gl/scene/gl_flats.cpp b/src/gl/scene/gl_flats.cpp
index fb5da4fd20..91c7f1c7e0 100644
--- a/src/gl/scene/gl_flats.cpp
+++ b/src/gl/scene/gl_flats.cpp
@@ -424,7 +424,7 @@ void GLFlat::Draw(int pass)
 		if (renderstyle==STYLE_Add) gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE);
 		gl_SetColor(lightlevel, rel, Colormap, alpha);
 		gl_SetFog(lightlevel, rel, &Colormap, false);
-		gl_RenderState.AlphaFunc(GL_GEQUAL,gl_mask_threshold*(alpha));
+		gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_threshold);
 		if (!gltexture)	
 		{
 			gl_RenderState.EnableTexture(false);
diff --git a/src/gl/scene/gl_portal.cpp b/src/gl/scene/gl_portal.cpp
index 922269636f..0cc602967b 100644
--- a/src/gl/scene/gl_portal.cpp
+++ b/src/gl/scene/gl_portal.cpp
@@ -998,7 +998,7 @@ void GLHorizonPortal::DrawContents()
 	gltexture->Bind();
 
 	gl_SetPlaneTextureRotation(sp, gltexture);
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.BlendFunc(GL_ONE,GL_ZERO);
 	gl_RenderState.Apply();
 
diff --git a/src/gl/scene/gl_scene.cpp b/src/gl/scene/gl_scene.cpp
index bf11730aab..e6dc3098c0 100644
--- a/src/gl/scene/gl_scene.cpp
+++ b/src/gl/scene/gl_scene.cpp
@@ -345,7 +345,7 @@ void FGLRenderer::RenderScene(int recursion)
 	glDepthFunc(GL_LESS);
 
 
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 
 	glDisable(GL_POLYGON_OFFSET_FILL);	// just in case
 
@@ -374,8 +374,6 @@ void FGLRenderer::RenderScene(int recursion)
 	gl_drawinfo->drawlists[GLDL_LIGHTFOG].Draw(pass);
 
 
-	gl_RenderState.EnableAlphaTest(true);
-
 	// Part 2: masked geometry. This is set up so that only pixels with alpha>0.5 will show
 	if (!gl_texture) 
 	{
@@ -383,7 +381,7 @@ void FGLRenderer::RenderScene(int recursion)
 		gl_RenderState.SetTextureMode(TM_MASK);
 	}
 	if (pass == GLPASS_BASE) pass = GLPASS_BASE_MASKED;
-	gl_RenderState.AlphaFunc(GL_GEQUAL,gl_mask_threshold);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_threshold);
 	gl_drawinfo->drawlists[GLDL_MASKED].Sort();
 	gl_drawinfo->drawlists[GLDL_MASKED].Draw(pass);
 	gl_drawinfo->drawlists[GLDL_FOGMASKED].Sort();
@@ -440,10 +438,10 @@ void FGLRenderer::RenderScene(int recursion)
 		glDepthFunc(GL_LEQUAL);
 		if (gl_texture) 
 		{
-			gl_RenderState.EnableAlphaTest(false);
+			gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 			gl_drawinfo->drawlists[GLDL_LIGHT].Sort();
 			gl_drawinfo->drawlists[GLDL_LIGHT].Draw(GLPASS_TEXTURE);
-			gl_RenderState.EnableAlphaTest(true);
+			gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_threshold);
 			gl_drawinfo->drawlists[GLDL_LIGHTBRIGHT].Sort();
 			gl_drawinfo->drawlists[GLDL_LIGHTBRIGHT].Draw(GLPASS_TEXTURE);
 			gl_drawinfo->drawlists[GLDL_LIGHTMASKED].Sort();
@@ -495,10 +493,9 @@ void FGLRenderer::RenderScene(int recursion)
 	
 	glDepthMask(false);							// don't write to Z-buffer!
 	gl_RenderState.EnableFog(true);
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.BlendFunc(GL_ONE,GL_ZERO);
 	gl_drawinfo->DrawUnhandledMissingTextures();
-	gl_RenderState.EnableAlphaTest(true);
 	glDepthMask(true);
 
 	glPolygonOffset(0.0f, 0.0f);
@@ -523,8 +520,7 @@ void FGLRenderer::RenderTranslucent()
 	gl_RenderState.SetCameraPos(FIXED2FLOAT(viewx), FIXED2FLOAT(viewy), FIXED2FLOAT(viewz));
 
 	// final pass: translucent stuff
-	gl_RenderState.EnableAlphaTest(true);
-	gl_RenderState.AlphaFunc(GL_GEQUAL,gl_mask_sprite_threshold);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_sprite_threshold);
 	gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
 	gl_RenderState.EnableBrightmap(true);
@@ -534,7 +530,7 @@ void FGLRenderer::RenderTranslucent()
 
 	glDepthMask(true);
 
-	gl_RenderState.AlphaFunc(GL_GEQUAL,0.5f);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.5f);
 	RenderAll.Unclock();
 }
 
@@ -577,7 +573,7 @@ void FGLRenderer::DrawScene(bool toscreen)
 
 static void FillScreen()
 {
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.EnableTexture(false);
 	gl_RenderState.Apply();
 	FFlatVertex *ptr = GLRenderer->mVBO->GetBuffer();
@@ -756,7 +752,6 @@ void FGLRenderer::EndDrawScene(sector_t * viewsector)
 	gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 	gl_RenderState.ResetColor();
 	gl_RenderState.EnableTexture(true);
-	gl_RenderState.EnableAlphaTest(true);
 	glDisable(GL_SCISSOR_TEST);
 }
 
diff --git a/src/gl/scene/gl_skydome.cpp b/src/gl/scene/gl_skydome.cpp
index d2014c6542..240bf67620 100644
--- a/src/gl/scene/gl_skydome.cpp
+++ b/src/gl/scene/gl_skydome.cpp
@@ -472,7 +472,7 @@ void GLSkyPortal::DrawContents()
 
 	gl_RenderState.ResetColor();
 	gl_RenderState.EnableFog(false);
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
 	gl_MatrixStack.Push(gl_RenderState.mViewMatrix);
@@ -481,7 +481,6 @@ void GLSkyPortal::DrawContents()
 	if (origin->texture[0] && origin->texture[0]->tex->gl_info.bSkybox)
 	{
 		RenderBox(origin->skytexno1, origin->texture[0], origin->x_offset[0], origin->sky2);
-		gl_RenderState.EnableAlphaTest(true);
 	}
 	else
 	{
@@ -495,8 +494,7 @@ void GLSkyPortal::DrawContents()
 			gl_RenderState.SetTextureMode(TM_MODULATE);
 		}
 		
-		gl_RenderState.EnableAlphaTest(true);
-		gl_RenderState.AlphaFunc(GL_GEQUAL,0.05f);
+		gl_RenderState.AlphaFunc(GL_GEQUAL, 0.05f);
 		
 		if (origin->doublesky && origin->texture[1])
 		{
diff --git a/src/gl/scene/gl_sprite.cpp b/src/gl/scene/gl_sprite.cpp
index ab0586f586..c70422b323 100644
--- a/src/gl/scene/gl_sprite.cpp
+++ b/src/gl/scene/gl_sprite.cpp
@@ -137,11 +137,11 @@ void GLSprite::Draw(int pass)
 
 		if (hw_styleflags == STYLEHW_NoAlphaTest)
 		{
-			gl_RenderState.EnableAlphaTest(false);
+			gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 		}
 		else
 		{
-			gl_RenderState.AlphaFunc(GL_GEQUAL,trans*gl_mask_sprite_threshold);
+			gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_sprite_threshold);
 		}
 
 		if (RenderStyle.BlendOp == STYLEOP_Shadow)
@@ -165,7 +165,7 @@ void GLSprite::Draw(int pass)
 				minalpha*=factor;
 			}
 
-			gl_RenderState.AlphaFunc(GL_GEQUAL,minalpha*gl_mask_sprite_threshold);
+			gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_sprite_threshold);
 			gl_RenderState.SetColor(0.2f,0.2f,0.2f,fuzzalpha, Colormap.desaturation);
 			additivefog = true;
 		}
@@ -294,16 +294,6 @@ void GLSprite::Draw(int pass)
 		gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 		gl_RenderState.BlendEquation(GL_FUNC_ADD);
 		gl_RenderState.SetTextureMode(TM_MODULATE);
-
-		// [BB] Restore the alpha test after drawing a smooth particle.
-		if (hw_styleflags == STYLEHW_NoAlphaTest)
-		{
-			gl_RenderState.EnableAlphaTest(true);
-		}
-		else
-		{
-			gl_RenderState.AlphaFunc(GL_GEQUAL,gl_mask_sprite_threshold);
-		}
 	}
 
 	gl_RenderState.SetObjectColor(0xffffffff);
diff --git a/src/gl/scene/gl_walls_draw.cpp b/src/gl/scene/gl_walls_draw.cpp
index b932691de4..e28f6315c6 100644
--- a/src/gl/scene/gl_walls_draw.cpp
+++ b/src/gl/scene/gl_walls_draw.cpp
@@ -301,9 +301,8 @@ void GLWall::RenderFogBoundary()
 		int rel = rellight + getExtraLight();
 		gl_SetFog(lightlevel, rel, &Colormap, false);
 		gl_RenderState.SetEffect(EFF_FOGBOUNDARY);
-		gl_RenderState.EnableAlphaTest(false);
+		gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 		RenderWall(RWF_BLANK);
-		gl_RenderState.EnableAlphaTest(true);
 		gl_RenderState.SetEffect(EFF_NONE);
 	}
 }
@@ -349,7 +348,7 @@ void GLWall::RenderMirrorSurface()
 
 	// Restore the defaults for the translucent pass
 	gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-	gl_RenderState.AlphaFunc(GL_GEQUAL,0.5f*gl_mask_sprite_threshold);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_sprite_threshold);
 	glDepthFunc(GL_LESS);
 
 	// This is drawn in the translucent pass which is done after the decal pass
@@ -383,8 +382,8 @@ void GLWall::RenderTranslucentWall()
 	// and until that changes I won't fix this code for the new blending modes!
 	bool isadditive = RenderStyle == STYLE_Add;
 
-	if (!transparent) gl_RenderState.AlphaFunc(GL_GEQUAL,gl_mask_threshold*fabs(alpha));
-	else gl_RenderState.EnableAlphaTest(false);
+	if (!transparent) gl_RenderState.AlphaFunc(GL_GEQUAL, gl_mask_threshold);
+	else gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	if (isadditive) gl_RenderState.BlendFunc(GL_SRC_ALPHA,GL_ONE);
 
 	int extra;
@@ -408,7 +407,6 @@ void GLWall::RenderTranslucentWall()
 
 	// restore default settings
 	if (isadditive) gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-	if (transparent) gl_RenderState.EnableAlphaTest(true);
 
 	if (!gltexture)	
 	{
diff --git a/src/gl/scene/gl_weapon.cpp b/src/gl/scene/gl_weapon.cpp
index 219eaf1156..d0f2ab3708 100644
--- a/src/gl/scene/gl_weapon.cpp
+++ b/src/gl/scene/gl_weapon.cpp
@@ -151,7 +151,7 @@ void FGLRenderer::DrawPSprite (player_t * player,pspdef_t *psp,fixed_t sx, fixed
 
 	if (tex->GetTransparent() || OverrideShader != 0)
 	{
-		gl_RenderState.EnableAlphaTest(false);
+		gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	}
 	gl_RenderState.Apply();
 	FFlatVertex *ptr = GLRenderer->mVBO->GetBuffer();
@@ -164,10 +164,7 @@ void FGLRenderer::DrawPSprite (player_t * player,pspdef_t *psp,fixed_t sx, fixed
 	ptr->Set(x2, y2, 0, fU2, fV2);
 	ptr++;
 	GLRenderer->mVBO->RenderCurrent(ptr, GL_TRIANGLE_STRIP);
-	if (tex->GetTransparent() || OverrideShader != 0)
-	{
-		gl_RenderState.EnableAlphaTest(true);
-	}
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.5f);
 }
 
 //==========================================================================
diff --git a/src/gl/shaders/gl_shader.cpp b/src/gl/shaders/gl_shader.cpp
index 1dbdada246..4373955c22 100644
--- a/src/gl/shaders/gl_shader.cpp
+++ b/src/gl/shaders/gl_shader.cpp
@@ -203,6 +203,7 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 	muInterpolationFactor.Init(hShader, "uInterpolationFactor");
 	muClipHeightTop.Init(hShader, "uClipHeightTop");
 	muClipHeightBottom.Init(hShader, "uClipHeightBottom");
+	muAlphaThreshold.Init(hShader, "uAlphaThreshold");
 
 	timer_index = glGetUniformLocation(hShader, "timer");
 	lights_index = glGetUniformLocation(hShader, "lights");
diff --git a/src/gl/shaders/gl_shader.h b/src/gl/shaders/gl_shader.h
index 663d09122f..bed37cbb03 100644
--- a/src/gl/shaders/gl_shader.h
+++ b/src/gl/shaders/gl_shader.h
@@ -195,6 +195,7 @@ class FShader
 	FBufferedUniform1f muInterpolationFactor;
 	FBufferedUniform1f muClipHeightTop;
 	FBufferedUniform1f muClipHeightBottom;
+	FBufferedUniform1f muAlphaThreshold;
 	
 	int timer_index;
 	int lights_index;
diff --git a/src/gl/system/gl_framebuffer.cpp b/src/gl/system/gl_framebuffer.cpp
index e34eb5fce2..d3783fd425 100644
--- a/src/gl/system/gl_framebuffer.cpp
+++ b/src/gl/system/gl_framebuffer.cpp
@@ -150,7 +150,6 @@ void OpenGLFrameBuffer::InitializeState()
 	glEnable(GL_TEXTURE_2D);
 	glDisable(GL_LINE_SMOOTH);
 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-	glAlphaFunc(GL_GEQUAL,0.5f);
 	glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
 	glHint(GL_POLYGON_SMOOTH_HINT, GL_NICEST);
 
diff --git a/src/gl/system/gl_system.h b/src/gl/system/gl_system.h
index 8140904a28..8273960f9e 100644
--- a/src/gl/system/gl_system.h
+++ b/src/gl/system/gl_system.h
@@ -68,15 +68,13 @@
 
 //GL headers
 #include <GL/glew.h>
+//#include "gl_load.h"
 
 #if defined(__APPLE__)
 	#include <OpenGL/OpenGL.h>
 #elif defined(__unix__)
 	//#include <GL/glxew.h>
 #else // !__APPLE__ && !__unix__
-	#define DWORD WINDOWS_DWORD	// I don't want to depend on this throughout the GL code!
-	#include <GL/wglew.h>
-	#undef DWORD
 #endif
 
 #ifdef _WIN32
diff --git a/src/gl/system/gl_wipe.cpp b/src/gl/system/gl_wipe.cpp
index e4627fd353..12e7c9e02d 100644
--- a/src/gl/system/gl_wipe.cpp
+++ b/src/gl/system/gl_wipe.cpp
@@ -280,7 +280,7 @@ bool OpenGLFrameBuffer::Wiper_Crossfade::Run(int ticks, OpenGLFrameBuffer *fb)
 	float vb = fb->GetHeight() / FHardwareTexture::GetTexDimension(fb->GetHeight());
 
 	gl_RenderState.SetTextureMode(TM_OPAQUE);
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.ResetColor();
 	gl_RenderState.Apply();
 	fb->wipestartscreen->Bind(0);
@@ -302,7 +302,7 @@ bool OpenGLFrameBuffer::Wiper_Crossfade::Run(int ticks, OpenGLFrameBuffer *fb)
 	gl_RenderState.SetColorAlpha(0xffffff, clamp(Clock/32.f, 0.f, 1.f));
 	gl_RenderState.Apply();
 	GLRenderer->mVBO->RenderArray(GL_TRIANGLE_STRIP, offset, count);
-	gl_RenderState.EnableAlphaTest(true);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.5f);
 	gl_RenderState.SetTextureMode(TM_MODULATE);
 
 	return Clock >= 32;
@@ -490,7 +490,7 @@ bool OpenGLFrameBuffer::Wiper_Burn::Run(int ticks, OpenGLFrameBuffer *fb)
 
 	// Put the initial screen back to the buffer.
 	gl_RenderState.SetTextureMode(TM_OPAQUE);
-	gl_RenderState.EnableAlphaTest(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
 	gl_RenderState.ResetColor();
 	gl_RenderState.Apply();
 	fb->wipestartscreen->Bind(0);
diff --git a/wadsrc/static/shaders/glsl/main.fp b/wadsrc/static/shaders/glsl/main.fp
index 5655493bdd..30a815b3cc 100644
--- a/wadsrc/static/shaders/glsl/main.fp
+++ b/wadsrc/static/shaders/glsl/main.fp
@@ -223,6 +223,12 @@ void main()
 #endif
 
 	vec4 frag = ProcessTexel();
+	
+#ifndef NO_DISCARD
+	// alpha testing
+	if (frag.a <= uAlphaThreshold) discard;
+#endif
+
 
 	switch (uFixedColormap)
 	{
diff --git a/wadsrc/static/shaders/glsl/main.vp b/wadsrc/static/shaders/glsl/main.vp
index 58ca931fb2..7a434ccbe3 100644
--- a/wadsrc/static/shaders/glsl/main.vp
+++ b/wadsrc/static/shaders/glsl/main.vp
@@ -52,8 +52,8 @@ void main()
 	
 	#ifdef SPHEREMAP
 		vec3 u = normalize(eyeCoordPos.xyz);
-		vec3 n = normalize(TextureMatrix * vec4(tc.x, 0.0, tc.y, 0.0);	// use texture matrix and coordinates for our normal. Since this is only used on walls, the normal's y coordinate is always 0.
-		vec3 r = reflect(u, n);
+		vec4 n = normalize(TextureMatrix * vec4(tc.x, 0.0, tc.y, 0.0));	// use texture matrix and coordinates for our normal. Since this is only used on walls, the normal's y coordinate is always 0.
+		vec3 r = reflect(u, n.xyz);
 		float m = 2.0 * sqrt( r.x*r.x + r.y*r.y + (r.z+1.0)*(r.z+1.0) );
 		vec2 sst = vec2(r.x/m + 0.5,  r.y/m + 0.5);
 		gl_TexCoord[0].xy = sst;
diff --git a/wadsrc/static/shaders/glsl/shaderdefs.i b/wadsrc/static/shaders/glsl/shaderdefs.i
index 867e9a7096..56e6965b21 100644
--- a/wadsrc/static/shaders/glsl/shaderdefs.i
+++ b/wadsrc/static/shaders/glsl/shaderdefs.i
@@ -4,6 +4,7 @@ uniform vec4 uCameraPos;
 uniform float uClipHeightTop, uClipHeightBottom;
 
 uniform int uTextureMode;
+uniform float uAlphaThreshold;
 
 // colors
 uniform vec4 uObjectColor;
@@ -34,8 +35,7 @@ uniform int uFogEnabled;
 // dynamic lights
 uniform ivec4 uLightRange;
 
-
-// redefine the matrix names to what they actually represent.
+// matrices
 uniform mat4 ProjectionMatrix;
 uniform mat4 ViewMatrix;
 uniform mat4 ModelMatrix;