Compute shader: Property at kernel index is not set

Question

I am trying to follow this excellent Coding Adventure: https://www.youtube.com/watch?v=lctXaT9pxA0 in order to get a very simple mesh deformation on a mesh using a compute shader.

I'm getting an error that reads:

Compute shader (NewComputeShader): Property (vertices) at kernel index (0) is not set UnityEngine.ComputeShader:Dispatch(Int32, Int32, Int32, Int32) MoonShader:runShader() (at Assets/MoonShader.cs:27) MoonShader:Update() (at Assets/MoonShader.cs:15)

I'm calling runShader() in Update (maybe that's a terrible idea, but I don't think it's contributing to this specific problem yet).

Do I need to somehow pass my mesh's vertices into StructuredBuffer<float3> vertices;? If so, how am I supposed to do that?

This is the call to the compute shader in my .cs file.

void runShader() {
    int kernelHandle = computeShader.FindKernel("CSMain");
    computeShader.Dispatch(kernelHandle, 512, 1, 1); //this is the line it appears to be complaining about
}

This is my .compute file.

#pragma kernel CSMain
StructuredBuffer<float3> vertices;
RWStructuredBuffer<float> heights;
uint numVertices;
float testValue = 20;

[numthreads(512,1,1)]
void CSMain (uint id : SV_DispatchThreadID) {
    if(id >= numVertices) {

    } else {
        float3 vertexPosition = vertices[id];
        heights[id] = 1 + sin(vertexPosition.y * testValue) * 0.05;
    }
}

Link to repo if it's helpful: https://github.com/glenpierce/proceduralPlanets

Answer 1

You need "link" your StructuredBuffer to a ComputeBuffer that you initialize in the CS script. In your code, you've never specified a compute shader to write to, so the compiler is basically saying, "yo, there's nowhere to write this data to!"

In your .cs file, you should have:

void runShader() {
    
    int kernelHandle = computeShader.FindKernel("CSMain");
    //New Things here
    ComputeBuffer vertexBuffer = new ComputeBuffer(mesh.vertices.Length, sizeof(float) * 3); //make new compute buffer with specified size, and specified "stride"
    //stride is like the size of each element, in your case it would be 3 floats, since Vector3 is 3 floats.
    vertexBuffer.setData(mesh.vertices); //set data inside buffer

    computeShader.setBuffer(kernelHandle, "vertices", vertexBuffer); //Linking the compute shader and cs shader buffers


    computeShader.Dispatch(kernelHandle, 512, 1, 1);
}

I hope that helps!

I'd also recommend checking out these two ComputeShader guides, the OP walks you through his own personal project and explains things pretty well.

(Easy) https://www.reddit.com/r/Unity3D/comments/7pa6bq/drawing_mandelbrot_fractal_using_gpu_compute/

(Hard) https://www.reddit.com/r/Unity3D/comments/7ppldz/physics_simulation_on_gpu_with_compute_shader_in/