Re: [PyOpenGL-Users] Suspiciously slow script

[Greg E. <gre...@ca...>]

Mike C. Fletcher wrote:
> it looks like on
> your driver the linear bitmap sampler is doing something non-optimal
> when it's sampling a (large) texture down across a large scale
> difference.

I would expect this to be slow using any driver. When there
is a large scale reduction, each pixel on the screen projects
onto a big block of texels in the texture. Doing linear
sampling on that requires scanning all of those texels and
averaging them together.

Using mipmaps, on the other hand, it's never necessary to
average more than four texels (or possibly eight, if you're
also interpolating between mipmap levels) for each screen
pixel.

Moral: Mipmaps are good. Use them!

-- 
Greg