Change Mesh colors in Compute Shader

Questions & Answers
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1

Hello everyone,

I have been working on a marching cube mesh generation game and would like to change the color of my mesh depending on the height of each vertex inside the mesh.
I could do it directly without compute shader but processing time was too long so I tried to move it to a compute shader.

Unfortunately I’m not so good with shaders so I’m now stuck …
For test pupose, I put all the vertiges of my mesh to blue and try to move it to red, I feel like once this base is done it will just be adding the scale and lerp the gradiant to get the colors I want.

If I run my shader now I get this error on each chunk:

ColorCompute.compute: Kernel at index (0) is invalid

And when clicking on the shader in my project folder I can see

array dimension must be literal scalar expression at kernel CSMain

Here is the script

public class ColorGenerator : MonoBehaviour
{
    //reference the marchingCube.compute shader that will be used later
    public ComputeShader ColorCompute;
    public Mesh ApplyColors(Mesh mesh, float chunkPositionY, Gradient heightGradient)
    {
        //Create the vertex count and assign the kernel id to an integer
        int vertexCount = mesh.vertexCount;
        int kernelID = ColorCompute.FindKernel("CSMain");
       // Create a compute buffer to hold vertex color data
        ComputeBuffer colorBuffer = new ComputeBuffer(vertexCount, sizeof(float) * 4, ComputeBufferType.Default);
        colorBuffer.SetData(mesh.colors);
        ColorCompute.SetBuffer(kernelID, "ColorBuffer", colorBuffer);
        // paramaters to calculate the color to apply
        ColorCompute.SetInt("numVertices", vertexCount);  // Pass the number of vertices
        // Dispatch the compute shader
        int threadGroups = Mathf.CeilToInt(vertexCount/ 256.0f);
        ColorCompute.SetInt("threadGroups", threadGroups);
        // Dispatch the compute shader
        ColorCompute.Dispatch(kernelID, threadGroups, 1, 1);
        // Get the modified vertex color data back from the compute buffer
        Color[] modifiedColors = new Color[vertexCount];
        colorBuffer.GetData(modifiedColors);
        // Update the mesh with the modified vertex colors
        mesh.colors = modifiedColors;
        return mesh;
    }
}

and the Shader

#pragma kernel CSMain
StructuredBuffer<float4> ColorBuffer;
uint numVertices;
uint threadGroups;
float4 modifiedColor;
[numthreads(threadGroups, 1, 1)]
void CSMain(uint3 id : SV_DispatchThreadID)
{
    float4 newColor[numVertices];
    // Evaluate the gradient at the computed position
    newColor[id.x].x = ColorBuffer[id.x].x + 1;
    newColor[id.x].y = ColorBuffer[id.x].y;
    newColor[id.x].z = ColorBuffer[id.x].z - 1;
    newColor[id.x].r = ColorBuffer[id.x].r;
    // Update the RGB channels of the vertex color
    ColorBuffer[id.x] = newColor;
}