add an attribute in the cpu-computing to pass something once to each vertex.
all things from cpu are read-only.
raycasting:
cast a ray into the computer to see if something touches a vertex. called raycasting.
post-processing:
ping-pong buffers.
have two buffers, apply one the destination becomes source, change destination; keep ping-ponging between them.
raw shader goes through shader-passes. you can make a shader and add it to an empty pass too., you need tDiffuse for that — that’s previous uv stuff.