Multi Pass Shaders

[torinmb]

Add ability to write to multiple buffers. This would allow post-processing + feedback loops.
We'd need to implement this feature in 3 different targets and also ensure it's turned off by default to support older versions.

[torinmb]

Potential helper library https://github.com/martinlaxenaire/three-multipass-post-processing. It's minimal, uses MIT license and is inspired by a blog post from a senior engineer from active theory that highlights optimizations for multipass

[torinmb]

from pete:

renderBufferA( () => {

  let c = enable2D() // really we want fragcoord?
  // let c = vec2("gl_FragCoord.xy", null, true);
  let val = readBufA(texCoord)
  color(val.x, val.y, val.z)
})

let s = getSpace()
let texCoord = vec2(s.x, s.y)
let val = readBufA(texCoord)
box(0.5, 0.5, 0.2+0.1*val)

[torinmb]

ToDo:

• Expose Sampler2D / Texture in JS
• implement separatePasses to extract passes from tree and return as separate dictionaries
• Figure out how to handle buffer initialization (should it be a setup function call where you can write your own SP shader that runs for 1 frame, or is it more helpful to be able to handle a single frame in the body of your buffer code? Eg. there's a boolean exposed )
• start to implement multiple buffers in targets

renderBufferA( () => {
  setupBuffer(() => {

  });
  color(val.x, val.y, val.z)
})

[PWhiddy]

Updated TODO

• Expose sampler2D/texture in js
• implement a multipass to GLSL func (prepends common tab to other passes and then runs them through sculptToGLSL
• Resolve the buffer initialization debacle
• implement targets

[torinmb]

Need an option to:

1. set RT wrap mode: between wrap, clear, hold, tile etc.
2. set min + mag filter using LinearFilter, or NearestFilter