   textures and blending
  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.   