Stateful Randomness in Shaders
I often find myself needing good random numbers in shaders, but this gets messy when you want to generate a bunch of different ones for each pixel. To get around this, I’m using a genuinely awful hack in DaeForth.
Implementation
:m rand-given-seed (| seed |)
[ seed seed 1141 * sin ]
[ 12.9898 78.233 ]
dot sin 43758.5453 * fract
;
@float global =pixel-seed
real-position /rand-given-seed \+ =pixel-seed
:m seed .7 rand-given-seed ;
:m gen-seed
seed =>cur-seed
cur-seed rand-given-seed =>next-seed
[ next-seed ] &seed def-macro
cur-seed
;
:m next-random gen-seed pixel-seed * store rand-given-seed ;
Each time you call next-random it generates a new, high-quality random number for the given pixel. Importantly, it does so with low overhead at runtime!
Example
For instance, this generates two random colors and then mixes them randomly (for a total of 7...