Resolved How to properly store all values to a compute buffer?

Hi,

I have followed the three eyed raytracer guide to ray tracing with the aim to trace the propagation of the rays. I therefore want to store the data of each ray. I am new to shaders and therefore my knowledge is lacking.

The problem I have is that I am unsure on how to store ALL my data into a RWStructuredBuffer. Should I use the SV_GroupIndex with the DispatchId somehow? The current solution is something I randomly found, it seems to work fine as I now can see the data of more rays than before (than by just using id.x or id.y), but I am unsure what I am actually doing here,

 uint index = id.x + id.y * 64;

. How should one go about this problem? As far as I have seen there are no 2D arrays in HLSL and moreover arrays cannot be sent via compute buffer as it is not a blittable type?

Edit: All I had to do was to multiply above with the amount the width specified in the dispatch call to get a correct result.

Code (HLSL):

1. [numthreads(64,1,1)]
2. void CSMain(uint3 id : SV_DispatchThreadID, int id2 : SV_GroupIndex)
3. {
4.     _Pixel = id.xy;
5.  
6.     uint index = id.x + id.y * 64;
7.  
8.     // Get the dimensions of the RenderTexture
9.     uint width, height;
10.     Result.GetDimensions(width, height);
11.  
12.     // Transform pixel to [-1,1] range
13.     float2 uv = float2((id.xy + _PixelOffset) / float2(width, height) * 2.0f - 1.0f);
14.  
15.     // Get a ray for the UVs
16.     Ray ray = CreateCameraRay(uv);
17.  
18.     RayData rayData;
19.     // Trace and shade the ray
20.     float3 result = float3(0, 0, 0);
21.     for (int i = 0; i < 8; i++)
22.     {
23.         RayHit hit = Trace(ray);
24.         result += ray.energy * Shade(ray, hit);
25.              
26.         if (!any(ray.energy))
27.             break;
28.      
29.         rayData.direction = ray.direction;
30.         rayData.energy = ray.energy;
31.         // we want total distance of one ray
32.         rayData.origin = ray.origin;
33.         rayData.distance += hit.distance;
34.      }
35.  
36.     _Rays[index] = rayData;
37.  
38.     Result[id.xy] = float4(result, 1);
39. }

Code (CSharp):

1.         // Set the target and dispatch the compute shader
2.         RayTracingShader.SetTexture(0, "Result", _target);
3.         int threadGroupsX = Mathf.CeilToInt(Screen.width / 64.0f);
4.         int threadGroupsY = Mathf.CeilToInt(Screen.height ); /// 8.0f
5.         RayTracingShader.Dispatch(0, threadGroupsX, threadGroupsY, 1);

Thanks in advance!