Re: [Flightgear-devel] Functions to textures?

[Chris F. <ch...@ij...>]

> Somewhat inversely, I'm also wondering if a simple texture1D() lookup might not be faster than evaluating the light function e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d)) three times to get an (rgb)-triplet.

That depends a lot on the GPU, and how coherent the texture
coordinates are across a triangle. You also need enough ALU work
elsewhere in the shader to mask the latency of the texture lookup.

For the existing noise texture generation, take a look at
make3DNoiseImage in scene/material/TextureBuilder.cxx in the simgear
tree. This particular texture is filled CPU-side, but if you're more
comfortable expressing things in a shader, you/someone could rig up
some FBO wiring to quickly render a shader-defined function into a
texture.

-- Chris