I've decided to change the src/dst blending operation to reverse subtract for an effect that I am doing. It appears that the result is not clamped to 0. It looks like it wraps passed the negatives and up to full color. Am I mistaken, or should it clamp to 0 when reverse subtracting? I've also decided to up the accuracy of my render-to texture. The texture is a normal map that gets generated during the scene. It is used to environment map an object. Before, I used D3DFMT_A8R8G8B8. The reflections work very well with D3DFMT_A16B16G16R16F. But a weird problem occurs with D3DFMT_A32B32G32R32F and D3DFMT_A16B16G16R16. My blending messes up. I have alphablending enabled, srcblend = srcalpha, destblend = one. When the latter 2 textures are used, it looks like alpha blending gets disabled. What kind of limitatios do I need to worry about when using different texture formats? Do I need to worry about anything special when I render to them? Thanks for any help.