(Unity) How to bake data (Vector3 and Color32) onto render textures? - unity3d

Question

With the recent introduction of VFX Graph, attribute maps are being used to 'Set Position/Color from Map'.
In order to get an attribute map, one must bake position and color data into render textures. But there is no reference to how to do this that I could find or even on the Unity docs.
Any help on how to do this will be appreciated!

Answer 1

Most of the time you would want to use a Compute Shader to bake a list of points into your textures. I'd suggest you check these repositories for reference:
Bake Skinned Mesh Renderer Data into textures
https://github.com/keijiro/Smrvfx
Bake Kinect data into textures
https://github.com/roelkok/Kinect-VFX-Graph
Bake pointcloud data into texture:
https://github.com/keijiro/Pcx
Personally, I'm using these scripts which work for my purpose though I'm no expert in Compute Shaders:
public class FramePositionBaker
{
ComputeShader bakerShader;
RenderTexture VFXpositionMap;
RenderTexture inputPositionTexture;
private ComputeBuffer positionBuffer;
const int texSize = 256;
public FramePositionBaker(RenderTexture _VFXPositionMap)
{
inputPositionTexture = new RenderTexture(texSize, texSize, 0, RenderTextureFormat.ARGBFloat);
inputPositionTexture.enableRandomWrite = true;
inputPositionTexture.Create();
bakerShader = (ComputeShader)Resources.Load("FramePositionBaker");
if (bakerShader == null)
{
Debug.LogError("[FramePositionBaker] baking shader not found in any Resources folder");
}
VFXpositionMap = _VFXPositionMap;
}
public void BakeFrame(ref Vector3[] vertices)
{
int pointCount = vertices.Length;
positionBuffer = new ComputeBuffer(pointCount, 3 * sizeof(float));
positionBuffer.SetData(vertices);
//Debug.Log("Length " + vertices.Length);
bakerShader.SetInt("dim", texSize);
bakerShader.SetTexture(0, "PositionTexture", inputPositionTexture);
bakerShader.SetBuffer(0, "PositionBuffer", positionBuffer);
bakerShader.Dispatch(0, (texSize / 8) + 1, (texSize / 8) + 1, 1);
Graphics.CopyTexture(inputPositionTexture, VFXpositionMap);
positionBuffer.Dispose();
}
}
The compute shader:
// Each #kernel tells which function to compile; you can have many kernels
#pragma kernel CSMain
// Create a RenderTexture with enableRandomWrite flag and set it
// with cs.SetTexture
RWTexture2D<float4> PositionTexture;
uint dim;
Buffer<float3> PositionBuffer;
[numthreads(8,8,1)]
void CSMain (uint3 id : SV_DispatchThreadID)
{
// TODO: insert actual code here!
uint index = id.y * dim + id.x;
uint lastIndex = PositionBuffer.Length - 1;
// Trick for generating a pseudo-random number.
// Inspired by a similar trick in Keijiro's PCX repo (BakedPointCloud.cs).
// The points that are in excess because of the square texture, point randomly to a point in the texture.
// e.g. if (index > lastIndex) index = 0 generates excessive particles in the first position, resulting in a visible artifact.
//if (index > lastIndex) index = ( index * 132049U ) % lastIndex;
float3 pos;
if (index > lastIndex && lastIndex != 0) {
//pos = 0;
index = ( index * 132049U ) % lastIndex;
}
pos = PositionBuffer[index];
PositionTexture[id.xy] = float4 (pos.x, pos.y, pos.z, 1);
}