- don't use uniforms related to fixed colormaps for other things.

The fixed colormap is a per-scene global setting that normally does not need to change ever during rendering of a scene so it's easily shoved aside into a static uniform buffer.
Having to change this buffer for inconsequential stuff should be avoided, especially when there's other uniforms that are just as good to hold these values.

src/gl/renderer/gl_renderer.cpp

@@ -565,7 +565,7 @@ void FGLRenderer::Draw2D(F2DDrawer *drawer)
 		{
 			if (!gl.legacyMode)
 			{
-				gl_RenderState.Set2DOverlayColor(cmd.mColor1);
+				gl_RenderState.SetFog(cmd.mColor1, 0);
 				gl_RenderState.SetFixedColormap(CM_PLAIN2D);
 			}
 			else if (cmd.mDesaturate > 0)

src/gl/renderer/gl_renderstate.cpp

@@ -221,25 +221,9 @@ bool FRenderState::ApplyShader()
 		activeShader->currentcliplinestate = 0;
 	}
 
-	if (mColormapState < -1)	// 2D operations
+	if (mColormapState == CM_PLAIN2D)	// 2D operations
 	{
-		if (mColormapState != CM_SPECIAL2D)
-		{
-			activeShader->muColormapStart.Set(m2DColors[0]);
-			activeShader->muFixedColormap.Set(4);
-		}
-		else
-		{
-			float startr = m2DColors[0].r / 255.f;
-			float startg = m2DColors[0].g / 255.f;
-			float startb = m2DColors[0].b / 255.f;
-			float ranger = m2DColors[1].r / 255.f - startr;
-			float rangeg = m2DColors[1].g / 255.f - startg;
-			float rangeb = m2DColors[1].b / 255.f - startb;
-			activeShader->muColormapStart.Set(startr, startg, startb, 0.f);
-			activeShader->muColormapRange.Set(ranger, rangeg, rangeb, 0.f);
-			activeShader->muFixedColormap.Set(1);
-		}
+		activeShader->muFixedColormap.Set(4);
 		activeShader->currentfixedcolormap = mColormapState;
 	}
 	else if (mColormapState != activeShader->currentfixedcolormap)

src/gl/renderer/gl_renderstate.h

@@ -112,7 +112,6 @@ class FRenderState
 	PalEntry mFogColor;
 	PalEntry mObjectColor;
 	PalEntry mObjectColor2;
-	PalEntry m2DColors[2];	// in the shader these will reuse the colormap ramp uniforms.
 	FStateVec4 mDynColor;
 	float mClipSplit[2];
 
@@ -402,11 +401,6 @@ public:
 		mObjectColor2 = pe;
 	}
 
-	void Set2DOverlayColor(PalEntry pe)
-	{
-		m2DColors[0] = pe;
-	}
-
 	void SetSpecular(float glossiness, float specularLevel)
 	{
 		mGlossiness = glossiness;

src/gl/scene/gl_sprite.cpp

@@ -266,12 +266,12 @@ void FDrawInfo::DrawSprite(GLSprite *sprite, int pass)
 			{
 				// If we get here we know that we have colored fog and no fixed colormap.
 				mDrawer->SetFog(sprite->foglevel, rel, &sprite->Colormap, additivefog);
-				gl_RenderState.SetFixedColormap(CM_FOGLAYER);
+				gl_RenderState.SetTextureMode(TM_FOGLAYER);
 				gl_RenderState.BlendEquation(GL_FUNC_ADD);
 				gl_RenderState.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 				gl_RenderState.Apply();
 				qd.Render(GL_TRIANGLE_STRIP);
-				gl_RenderState.SetFixedColormap(CM_DEFAULT);
+				gl_RenderState.SetTextureMode(TM_MODULATE);
 			}
 		}
 		else

src/gl_load/gl_interface.h

@@ -21,6 +21,7 @@ enum TexMode
 	TM_REDTOALPHA,		// (1, 1, 1, r)
 	TM_CLAMPY,			// (r, g, b, (t >= 0.0 && t <= 1.0)? a:0)
 	TM_INVERTOPAQUE,	// (1-r, 1-g, 1-b, 1)
+	TM_FOGLAYER,		// (renders a fog layer in the shape of the active texture)
 };
 
 enum ELightMethod

wadsrc/static/shaders/glsl/main.fp

@@ -89,6 +89,9 @@ vec4 getTexel(vec2 st)
 		case 6: // TM_OPAQUEINVERSE
 			texel = vec4(1.0-texel.r, 1.0-texel.b, 1.0-texel.g, 1.0);
 			break;
+			
+		case 7: //TM_FOGLAYER 
+			return texel;
 	}
 	if (uObjectColor2.a == 0.0) texel *= uObjectColor;
 	else texel *= mix(uObjectColor, uObjectColor2, glowdist.z);
@@ -428,7 +431,27 @@ void main()
 	if (frag.a <= uAlphaThreshold) discard;
 #endif
 
-	switch (uFixedColormap)
+	if (uTextureMode == 7)
+	{
+		float fogdist;
+		float fogfactor;
+		
+		//
+		// calculate fog factor
+		//
+		if (uFogEnabled == -1) 
+		{
+			fogdist = pixelpos.w;
+		}
+		else 
+		{
+			fogdist = max(16.0, distance(pixelpos.xyz, uCameraPos.xyz));
+		}
+		fogfactor = exp2 (uFogDensity * fogdist);
+		
+		frag = vec4(uFogColor.rgb, (1.0 - fogfactor) * frag.a * 0.75 * vColor.a);
+	}
+	else switch (uFixedColormap)
 	{
 		case 0:	// in-game rendering.
 		{
@@ -480,32 +503,15 @@ void main()
 			break;
 		}
 
-		case 3:	// fog layer
+		case 3:	// unused
 		{
-			float fogdist;
-			float fogfactor;
-			
-			//
-			// calculate fog factor
-			//
-			if (uFogEnabled == -1) 
-			{
-				fogdist = pixelpos.w;
-			}
-			else 
-			{
-				fogdist = max(16.0, distance(pixelpos.xyz, uCameraPos.xyz));
-			}
-			fogfactor = exp2 (uFogDensity * fogdist);
-			
-			frag = vec4(uFogColor.rgb, (1.0 - fogfactor) * frag.a * 0.75 * vColor.a);
 			break;
 		}
 		
 		case 4:	// simple 2D (reuses a uniform for the special colormap for the color overlay.)
 		{
 			frag = frag * ProcessLight(vColor);
-			frag.rgb = frag.rgb + uFixedColormapStart.rgb;
+			frag.rgb = frag.rgb + uFogColor.rgb;
 			break;
 		}