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n0ob

Alpha blending with A32B32G32R32 not working?

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Hello! I'm trying to render a texture to a A32B32G32R32 texture, with alpha blending. In the shader I'm enabling alpha blending, and as a test set source and dest blends to Zero. However, the alpha state stuff is completely being ignored, and the original color is coming through. I've tried making the source texture also A32B32G32R32, with no luck. Shouldn't I be able to alpha blend with this format? Thanks!

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Pretty sure that's an optional feature for cards. If you look in your DirectX Caps Viewer, I think it's under Adapter Formats => D3DFMT_XXX => Texture Formats. This should give you a list of all the supported texture formats, and for each format, what's supported. If memory serves correctly, alpha-blending with floating point render targets is an optional feature, even in DX10 I think. Could be wrong though!

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Ahh, thanks a ton! I think it was the 'post pixel shader blending' flag, which was 'no' for the full-precision format, but 'yes' for half-precision. So, I switched over to half-precision and it's working! It didn't occur to me that my awesome card couldn't handle blending :-P Thanks a ton!

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The other one to be careful about is filtering. ISTR ATI/AMD said they wouldn't support filtering on FP32 textures unless they had to as they didn't see it as being used for anything other than look-up data that should be point-sampled anyway. Not sure if they're still holding that line though.

Jack

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