Change destination alpha handling. The blending method introduced in rev 1921 was not the correct way to do it. This way was suggested by hrydgard in October and I should have listened. A simple pixel shader as hrydgard suggested cannot be used because the alpha is not set if the pixel is discarded due to failing depth (after z texture) or alpha (result of tev stages) tests. There is a bit of a performance hit so there should be an option to disable the second render pass which sets the alpha because it is probably not needed most of the time.

git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@2662 8ced0084-cf51-0410-be5f-012b33b47a6e

Source/Plugins/Plugin_VideoOGL/Src/BPStructs.cpp

@@ -153,7 +153,7 @@ void BPWritten(int addr, int changes, int newval)
             PRIM_LOG("constalpha: alp=%d, en=%d\n", bpmem.dstalpha.alpha, bpmem.dstalpha.enable);
 			SETSTAT(stats.dstAlphaEnable, bpmem.dstalpha.enable);
 			SETSTAT_UINT(stats.dstAlpha, bpmem.dstalpha.alpha);
-			Renderer::SetBlendMode(false);
+            PixelShaderManager::SetDestAlpha(bpmem.dstalpha);
         }
         break;