Automatic mipmap generation for floating point textures on nv40

OpenGL OpenGL: Advanced Coding
1

Hi,

I would like to use automatic mipmap generation on an nv40 for a floating point texture.
Currently I am crating this texture from a texture rectangle that was created with internal format GL_FLOAT_RGBA16_NV. I then create a new texture 2d of the same exact size of the rectangle and use an internal format of GL_FLOAT_RGBA16_NV or GL_RGBA_FLOAT16_ATI.
It would appear that when I enable the
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP_SGIS, GL_TRUE);
the copy texture command takes about 2-3 second to copy the image. With mipmap disabled, it only takes a fraction of a second.

I was wondering if

  1. mipmap generation is not implemented in hardware for 2d floating point textures on nv40
  2. if not, is there a problem copying from a rectangle to a 2d texture?

Thanks!

--fabio
2

If your texture dimensions are a power of 2 the mipmap generation should be done in hardware. If they are non power of 2, current drivers will fall back to software.