fixup: hack to cancel overbright on glow maps

Author: illwieckz

src/engine/renderer/glsl_source/lightMapping_fp.glsl

@@ -173,12 +173,26 @@ void main()
 		color.rgb += 0.7 * emission;
 	#endif
 
+	/* HACK: use sign to know if there is a light or not, and
+	then if it will receive overbright multiplication or not. */
+	if ( u_LightFactor > 0 )
+	{
+		color.rgb /= u_LightFactor;
+	}
+
 	#if defined(r_glowMapping)
 		// Blend glow map.
-		color.rgb += texture2D(u_GlowMap, texCoords).rgb;
-	#endif
+		vec3 glow = texture2D(u_GlowMap, texCoords).rgb;
+
+		/* HACK: use sign to know if there is a light or not, and
+		then if it will receive overbright multiplication or not. */
+		if ( u_LightFactor < 0 )
+		{
+			glow /= - u_LightFactor;
+		}
 
-	color.rgb /= u_LightFactor;
+		color.rgb += glow;
+	#endif
 
 	outputColor = color;
 

src/engine/renderer/tr_shade.cpp

@@ -576,13 +576,22 @@ void SetNormalScale( shaderStage_t *pStage, vec3_t normalScale )
 	normalScale[ 2 ] *= r_normalScale->value;
 }
 
-static float cancelLightFactor( shaderStage_t *pStage )
+static float cancelLightFactor( shaderStage_t *pStage, bool hack = false )
 {
 	// We should cancel overbrightBits if there is no light,
 	// and it's not using blendFunc dst_color.
 	bool blendFunc_dstColor = ( pStage->stateBits & GLS_SRCBLEND_BITS ) == GLS_SRCBLEND_DST_COLOR;
 
-	return ( pStage->shaderHasNoLight && !blendFunc_dstColor ) ? tr.mapLightFactor : 1.0f;
+	if ( hack )
+	{
+		/* HACK: use sign to know if there is a light or not, and
+		then if it will receive overbright multiplication or not. */
+		return ( pStage->shaderHasNoLight && !blendFunc_dstColor ) ? tr.mapLightFactor : - tr.mapLightFactor;
+	}
+	else
+	{
+		return ( pStage->shaderHasNoLight && !blendFunc_dstColor ) ? tr.mapLightFactor : 1.0f;
+	}
 }
 
 // *INDENT-ON*
@@ -1078,7 +1087,7 @@ static void Render_lightMapping( shaderStage_t *pStage )
 	gl_lightMappingShader->SetUniform_Time( backEnd.refdef.floatTime - backEnd.currentEntity->e.shaderTime );
 
 	// u_LightFactor
-	gl_lightMappingShader->SetUniform_LightFactor( cancelLightFactor( pStage ) );
+	gl_lightMappingShader->SetUniform_LightFactor( cancelLightFactor( pStage, true ) );
 
 	// u_ColorModulate
 	gl_lightMappingShader->SetUniform_ColorModulate( colorGen, alphaGen );