NUKE alphaAddOne bit in color modulate

There are no differences in my screenshot test suite as a result of
removing this. This alpha := 1 thing only existed in the `generic`
shader; its absence in lightMapping is further evidence suggesting it is
not needed.

Note: this would open opportunities for further
improvements/cleanup/simplification, due to e.g. the now unused spot in
the float color modulate array, but I'm about to NUKE a large part of
this code on the 0.56 branch so let's not touch it.

Author: slipher

src/engine/renderer/gl_shader.h

@@ -2738,7 +2738,6 @@ struct colorModulation_t {
 	float alphaGen = 0.0f;
 	float lightFactor = 1.0f;
 	bool useVertexLightFactor = false;
-	bool alphaAddOne = true;
 };
 
 static colorModulation_t ColorModulateColorGen(
@@ -2752,8 +2751,6 @@ static colorModulation_t ColorModulateColorGen(
 	switch ( colorGen )
 	{
 		case colorGen_t::CGEN_VERTEX:
-			colorModulation.alphaAddOne = false;
-
 			if ( vertexOverbright )
 			{
 				// vertexOverbright is only needed for non-lightmapped cases. When there is a
@@ -2768,7 +2765,6 @@ static colorModulation_t ColorModulateColorGen(
 			break;
 
 		case colorGen_t::CGEN_ONE_MINUS_VERTEX:
-			colorModulation.alphaAddOne = false;
 			colorModulation.colorGen = -1.0f;
 			break;
 
@@ -2785,12 +2781,10 @@ static colorModulation_t ColorModulateColorGen(
 	switch ( alphaGen )
 	{
 		case alphaGen_t::AGEN_VERTEX:
-			colorModulation.alphaAddOne = false;;
 			colorModulation.alphaGen = 1.0f;
 			break;
 
 		case alphaGen_t::AGEN_ONE_MINUS_VERTEX:
-			colorModulation.alphaAddOne = false;;
 			colorModulation.alphaGen = -1.0f;
 			break;
 
@@ -2827,7 +2821,7 @@ class u_ColorModulateColorGen_Float :
 		colorModulate_Float[ 0 ] = colorModulation.colorGen;
 		colorModulate_Float[ 1 ] = colorModulation.lightFactor;
 		colorModulate_Float[ 1 ] *= colorModulation.useVertexLightFactor ? -1.0f : 1.0f;
-		colorModulate_Float[ 2 ] = colorModulation.alphaAddOne;
+		colorModulate_Float[ 2 ] = {};
 		colorModulate_Float[ 3 ] = colorModulation.alphaGen;
 
 		this->SetValue( colorModulate_Float );
@@ -2859,7 +2853,6 @@ class u_ColorModulateColorGen_Uint :
 			COLOR_MINUS_ONE = 1,
 			ALPHA_ONE = 2,
 			ALPHA_MINUS_ONE = 3,
-			ALPHA_ADD_ONE = 4,
 			// <-- Insert new bits there.
 			IS_LIGHT_STYLE = 27,
 			LIGHTFACTOR_BIT0 = 28,
@@ -2879,8 +2872,6 @@ class u_ColorModulateColorGen_Uint :
 			<< Util::ordinal( ColorModulate_Bit::ALPHA_ONE );
 		colorModulate_Uint |= ( colorModulation.alphaGen == -1.0f )
 			<< Util::ordinal( ColorModulate_Bit::ALPHA_MINUS_ONE );
-		colorModulate_Uint |= colorModulation.alphaAddOne
-			<< Util::ordinal( ColorModulate_Bit::ALPHA_ADD_ONE );
 		colorModulate_Uint |= colorModulation.useVertexLightFactor
 			<< Util::ordinal( ColorModulate_Bit::IS_LIGHT_STYLE );
 		colorModulate_Uint |= uint32_t( colorModulation.lightFactor )

src/engine/renderer/glsl_source/common.glsl

@@ -68,8 +68,7 @@ colorMod << 0: color * 1
 colorMod << 1: color * ( -1 )
 colorMod << 2: alpha * 1
 colorMod << 3: alpha * ( -1 )
-colorMod << 4: alpha = 1
-colorMod << 5-26: available for future usage
+colorMod << 4-26: available for future usage
 colorMod << 27: color += lightFactor
 colorMod << 28-31: lightFactor
 
@@ -78,7 +77,6 @@ colorMod float format:
 colorMod[ 0 ]: color * f
 colorMod[ 1 ] absolute value: lightFactor
 colorMod[ 1 ] minus sign: color += lightFactor
-colorMod[ 2 ]: alpha = 1
 colorMod[ 3 ]: alpha * f */
 
 vec4 ColorModulateToColor( const in colorModulatePack colorMod )
@@ -101,7 +99,6 @@ vec4 ColorModulateToColor( const in colorModulatePack colorMod )
 
 struct ModBits_t
 {
-	bool alphaAddOne;
 	bool useVertexLightFactor;
 };
 
@@ -110,10 +107,8 @@ ModBits_t ColorModulateToBits( const in colorModulatePack colorMod )
 	ModBits_t modBits;
 
 #if defined(HAVE_EXT_gpu_shader4)
-	modBits.alphaAddOne = bool( ( colorMod >> 4u ) & 1u );
 	modBits.useVertexLightFactor = bool( ( colorMod >> 27u ) & 1u );
 #else
-	modBits.alphaAddOne = colorMod.b != 0;
 	modBits.useVertexLightFactor = colorMod.g < 0;
 #endif
 
@@ -159,9 +154,6 @@ void ColorModulateColor_lightFactor(
 	ModBits_t modBits = ColorModulateToBits( colorMod );
 	float lightFactor = ColorModulateToLightFactor( colorMod );
 
-	// This is used to skip vertex colours if the colorMod doesn't need them.
-	color.a = modBits.alphaAddOne ? 1.0 : color.a;
-
 	colorModulation.rgb += vec3( modBits.useVertexLightFactor ? lightFactor : 0 );
 
 	vec4 unpackedColor = UnpackColor( packedColor );