Allow/require renderers to enable alpha blending when needed. Fixes voxel shadow issues.

OpenRA.FileFormats/Graphics/IGraphicsDevice.cs

@@ -54,6 +54,9 @@ namespace OpenRA.FileFormats.Graphics
 
 		void EnableDepthBuffer();
 		void DisableDepthBuffer();
+
+		void EnableAlphaBlending();
+		void DisableAlphaBlending();
 	}
 
 	public interface IVertexBuffer<T>

OpenRA.Game/Graphics/LineRenderer.cs

@@ -34,6 +34,7 @@ namespace OpenRA.Graphics
 		{
 			if (nv > 0)
 			{
+				renderer.Device.EnableAlphaBlending();
 				shader.Render(() =>
 				{
 					var vb = renderer.GetTempVertexBuffer();
@@ -41,7 +42,7 @@ namespace OpenRA.Graphics
 					renderer.SetLineWidth(LineWidth * Game.viewport.Zoom);
 					renderer.DrawBatch(vb, 0, nv, PrimitiveType.LineList);
 				});
-
+				renderer.Device.DisableAlphaBlending();
 				nv = 0;
 			}
 		}

OpenRA.Game/Graphics/QuadRenderer.cs

@@ -31,12 +31,14 @@ namespace OpenRA.Graphics
 		{
 			if (nv > 0)
 			{
+				renderer.Device.EnableAlphaBlending();
 				shader.Render(() =>
 				{
 					var vb = renderer.GetTempVertexBuffer();
 					vb.SetData(vertices, nv);
 					renderer.DrawBatch(vb, 0, nv, PrimitiveType.QuadList);
 				});
+				renderer.Device.DisableAlphaBlending();
 
 				nv = 0;
 			}

OpenRA.Game/Graphics/SpriteRenderer.cs

@@ -33,12 +33,14 @@ namespace OpenRA.Graphics
 			if (nv > 0)
 			{
 				shader.SetTexture("DiffuseTexture", currentSheet.Texture);
+				renderer.Device.EnableAlphaBlending();
 				shader.Render(() =>
 				{
 					var vb = renderer.GetTempVertexBuffer();
 					vb.SetData(vertices, nv);
 					renderer.DrawBatch(vb, 0, nv, PrimitiveType.QuadList);
 				});
+				renderer.Device.DisableAlphaBlending();
 
 				nv = 0;
 				currentSheet = null;
@@ -99,7 +101,9 @@ namespace OpenRA.Graphics
 		public void DrawVertexBuffer(IVertexBuffer<Vertex> buffer, int start, int length, PrimitiveType type, Sheet sheet)
 		{
 			shader.SetTexture("DiffuseTexture", sheet.Texture);
+			renderer.Device.EnableAlphaBlending();
 			shader.Render(() => renderer.DrawBatch(buffer, start, length, type));
+			renderer.Device.DisableAlphaBlending();
 		}
 
 		public void SetPalette(ITexture palette)

OpenRA.Renderer.Gl/Shader.cs

@@ -104,7 +104,6 @@ namespace OpenRA.Renderer.Glsl
 					++nextTexUnit;
 				}
 			}
-
 		}
 
 		public void Render(Action a)
@@ -119,17 +118,9 @@ namespace OpenRA.Renderer.Glsl
 				Gl.glBindTexture(Gl.GL_TEXTURE_2D, ((Texture)kv.Value).ID);
 			}
 
-			/* configure blend state */
-			ErrorHandler.CheckGlError();
-			// TODO: Only enable alpha blending if we need it
-			Gl.glEnable(Gl.GL_BLEND);
-			ErrorHandler.CheckGlError();
-			Gl.glBlendFunc(Gl.GL_SRC_ALPHA, Gl.GL_ONE_MINUS_SRC_ALPHA);
 			ErrorHandler.CheckGlError();
 			a();
 			ErrorHandler.CheckGlError();
-			Gl.glDisable(Gl.GL_BLEND);
-			ErrorHandler.CheckGlError();
 		}
 
 		public void SetTexture(string name, ITexture t)

OpenRA.Renderer.Null/NullGraphicsDevice.cs

@@ -41,6 +41,9 @@ namespace OpenRA.Renderer.Null
 		public void EnableDepthBuffer() { }
 		public void DisableDepthBuffer() { }
 
+		public void EnableAlphaBlending() { }
+		public void DisableAlphaBlending() { }
+
 		public void Clear() { }
 		public void Present() { }
 

OpenRA.Renderer.SdlCommon/SdlGraphics.cs

@@ -148,6 +148,20 @@ namespace OpenRA.Renderer.SdlCommon
 			ErrorHandler.CheckGlError();
 		}
 
+		public void EnableAlphaBlending()
+		{
+			Gl.glEnable(Gl.GL_BLEND);
+			ErrorHandler.CheckGlError();
+			Gl.glBlendFunc(Gl.GL_SRC_ALPHA, Gl.GL_ONE_MINUS_SRC_ALPHA);
+			ErrorHandler.CheckGlError();
+		}
+
+		public void DisableAlphaBlending()
+		{
+			Gl.glDisable(Gl.GL_BLEND);
+			ErrorHandler.CheckGlError();
+		}
+
 		public void EnableScissor(int left, int top, int width, int height)
 		{
 			if (width < 0) width = 0;

cg/line.fx

@@ -30,7 +30,6 @@ float4 Simple_fp(VertexOut f) : COLOR0 {
 
 technique high_quality {
 	pass p0	{
-		BlendEnable = true;
 		DepthTestEnable = false;
 		//CullMode = None;
 		//FillMode = Wireframe;
@@ -44,7 +43,6 @@ technique high_quality {
 
 technique high_quality_cg21 {
 	pass p0	{
-		BlendEnable = true;
 		DepthTestEnable = false;
 		//CullMode = None;
 		//FillMode = Wireframe;

cg/rgba.fx

@@ -39,7 +39,6 @@ float4 Simple_fp(FragmentIn f) : COLOR0 {
 
 technique high_quality {
 	pass p0	{
-		BlendEnable = true;
 		DepthTestEnable = false;
 		CullFaceEnable = false;
 		VertexProgram = compile latest Simple_vp();
@@ -52,7 +51,6 @@ technique high_quality {
 
 technique high_quality_cg21 {
 	pass p0	{
-		BlendEnable = true;
 		DepthTestEnable = false;
 		CullFaceEnable = false;
 		VertexProgram = compile arbvp1 Simple_vp();

cg/shp.fx

@@ -55,7 +55,6 @@ float4 Palette_fp(VertexOut f) : COLOR0 {
 
 technique low_quality {
 	pass p0 {
-		BlendEnable = true;
 		DepthTestEnable = false;
 		CullFaceEnable = false;
 		VertexProgram = compile latest Simple_vp();
@@ -68,7 +67,6 @@ technique low_quality {
 
 technique low_quality_cg21 {
 	pass p0 {
-		BlendEnable = true;
 		DepthTestEnable = false;
 		CullFaceEnable = false;
 		VertexProgram = compile arbvp1 Simple_vp();

cg/vxl.fx

@@ -61,7 +61,6 @@ float4 Simple_fp(VertexOut f) : COLOR0 {
 
 technique high_quality {
 	pass p0 {
-		BlendEnable = true;
 		DepthTestEnable = true;
 		CullFaceEnable = false;
 		VertexProgram = compile latest Simple_vp();
@@ -74,7 +73,6 @@ technique high_quality {
 
 technique high_quality_cg21 {
 	pass p0 {
-		BlendEnable = true;
 		DepthTestEnable = true;
 		CullFaceEnable = false;
 		VertexProgram = compile arbvp1 Simple_vp();