Illuminate materials with no backface culling from both sides

This might need adaptions in some materials, but is probably the right thing
to do.

planet/Graphics.ocg/LightShader.glsl

@@ -4,6 +4,7 @@
 #ifdef HAVE_LIGHT
 uniform sampler2D lightTex;
 #endif
+uniform float cullMode; // 0 if backface culling is enabled, 1 if it is disabled
 
 // uncomment the following lines for debugging light directions:
 // yellow: light up, blue: light down, turqoise: light right, pink: light left
@@ -55,9 +56,9 @@ slice(texture+5)
 
 slice(light)
 {
-	float light = 2.0 * lightBright * max(dot(normal, lightDir), 0.0);
+	float light = 2.0 * lightBright * max(max(dot(normal, lightDir), 0.0), cullMode * max(dot(vec3(-normal.xy, normal.z), lightDir), 0.0));
 #ifdef HAVE_2PX
-	float light2 = 2.0 * lightBright * max(dot(normal2, lightDir), 0.0);
+	float light2 = 2.0 * lightBright * max(max(dot(normal2, lightDir), 0.0), cullMode * max(dot(vec3(-normal2.xy, normal2.z), lightDir), 0.0));
 #endif
 }
 

src/graphics/C4DrawGL.cpp

@@ -399,6 +399,8 @@ void CStdGL::SetupMultiBlt(C4ShaderCall& call, const C4BltTransform* pTransform,
 		call.SetUniformMatrix2x3fv(C4SSU_AmbientTransform, 1, ambientTransform);
 	}
 
+	call.SetUniform1f(C4SSU_CullMode, 0.0f);
+
 	// Apply zoom and transform
 	glPushMatrix();
 	glTranslatef(ZoomX, ZoomY, 0.0f);
@@ -580,6 +582,7 @@ bool CStdGL::CreateSpriteShader(C4Shader& shader, const char* name, int ssc, C4G
 	uniformNames[C4SSU_AmbientTransform] = "ambientTransform";
 	uniformNames[C4SSU_AmbientBrightness] = "ambientBrightness";
 	uniformNames[C4SSU_Bones] = "bones";
+	uniformNames[C4SSU_CullMode] = "cullMode";
 	uniformNames[C4SSU_Count] = NULL;
 
 	// Clear previous content

src/graphics/C4DrawGL.h

@@ -70,6 +70,7 @@ enum C4SS_Uniforms
 	C4SSU_AmbientBrightness, // C4SSC_LIGHT
 
 	C4SSU_Bones, // for meshes
+	C4SSU_CullMode, // for meshes
 
 	C4SSU_Count
 };

src/graphics/C4DrawMeshGL.cpp

@@ -415,7 +415,7 @@ namespace
 		return true;
 	}
 
-	void SetStandardUniforms(C4ShaderCall& call, DWORD dwModClr, DWORD dwPlayerColor, DWORD dwBlitMode, const C4FoWRegion* pFoW, const C4Rect& clipRect, const C4Rect& outRect)
+	void SetStandardUniforms(C4ShaderCall& call, DWORD dwModClr, DWORD dwPlayerColor, DWORD dwBlitMode, bool cullFace, const C4FoWRegion* pFoW, const C4Rect& clipRect, const C4Rect& outRect)
 	{
 		// Draw transform
 		const float fMod[4] = {
@@ -434,6 +434,9 @@ namespace
 		};
 		call.SetUniform3fv(C4SSU_OverlayClr, 1, fPlrClr);
 
+		// Backface culling flag
+		call.SetUniform1f(C4SSU_CullMode, cullFace ? 0.0f : 1.0f);
+
 		// Dynamic light
 		if(pFoW != NULL)
 		{
@@ -582,10 +585,12 @@ namespace
 
 			// Upload the current bone transformation matrixes (if there are any)
 			if (!bones.empty())
+			{
 				if (pGL->Workarounds.LowMaxVertexUniformCount)
 					glUniformMatrix3x4fv(shader->GetUniform(C4SSU_Bones), bones.size(), GL_FALSE, &bones[0].m[0][0]);
 				else
 					glUniformMatrix4x3fv(shader->GetUniform(C4SSU_Bones), bones.size(), GL_TRUE, &bones[0].m[0][0]);
+			}
 
 			// Bind the vertex data of the mesh
 #define VERTEX_OFFSET(field) reinterpret_cast<const uint8_t *>(offsetof(StdMeshVertex, field))
@@ -665,7 +670,7 @@ namespace
 			}
 
 			// Set uniforms and instance parameters
-			SetStandardUniforms(call, dwModClr, dwPlayerColor, dwBlitMode, pFoW, clipRect, outRect);
+			SetStandardUniforms(call, dwModClr, dwPlayerColor, dwBlitMode, pass.CullHardware != StdMeshMaterialPass::CH_None, pFoW, clipRect, outRect);
 			for(unsigned int i = 0; i < pass.Program->Parameters.size(); ++i)
 			{
 				const int uniform = pass.Program->Parameters[i].UniformIndex;

src/lib/StdMeshMaterial.cpp

@@ -863,6 +863,7 @@ bool StdMeshMaterialProgram::CompileShader(StdMeshMaterialLoader& loader, C4Shad
 	uniformNames[C4SSU_AmbientTransform] = "ambientTransform";
 	uniformNames[C4SSU_AmbientBrightness] = "ambientBrightness";
 	uniformNames[C4SSU_Bones] = "bones";
+	uniformNames[C4SSU_CullMode] = "cullMode";
 	for (unsigned int i = 0; i < ParameterNames.size(); ++i)
 		uniformNames[C4SSU_Count + i] = ParameterNames[i].getData();
 	uniformNames[C4SSU_Count + ParameterNames.size()] = NULL;