Resolved How to draw triangles using StructuredBuffers and Graphics.DrawProceduralNow?

I am very new to writing shaders and attempting to draw an arbitrary set of triangles from rapidly updated procedural data. I want to use the shader like this:

Code (CSharp):

1. void Render()
2. {
3.       // set whatever buffer data is needed
4.       _triangleMaterial.SetPass(0);
5.       Graphics.DrawProceduralNow(MeshTopology.Triangles, _triangleCount * 3);
6. }

I'm struggling to create the shader. Instead of modifying a mesh, I'd like to write the data to structured buffers. For each triangle I want to pass three vertex positions, three vertex normals, three vertex colors, and three vertex uvs.

Code (CSharp):

1. StructuredBuffer<float3> positionsBuffer;
2. StructuredBuffer<float3> normalsBuffer;
3. StructuredBuffer<float2> uvsBuffer;
4. StructuredBuffer<float4> colorsBuffer;

What do I need to do within the shader to make it work?

 

I got it to work. I forgot I needed to add the script specifically to the Camera GO instead of an empty GO.

Spoiler: TriangleTest.cs

Code (CSharp):

1.  
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.Rendering;
6. public class TrianglesTest : MonoBehaviour
7. {
8.  
9.     // Vertices Buffer
10.     ComputeBuffer _verticesBuffer;
11.  
12.     static readonly int verticesBuffer = Shader.PropertyToID("verticesBuffer");
13.  
14.     public Vector4[] vertices;
15.     public Material triangleMaterial;
16.  
17.     void Awake()
18.     {
19.         RenderPipelineManager.endFrameRendering += (arg1, arg2) => Render();
20.     }
21.  
22.     void OnPostRender()
23.     {
24.         Render();
25.     }
26.  
27.  
28.     void OnDrawGizmos()
29.     {
30.         Render();
31.     }
32.  
33.  
34.     void CopyFromCpuToGpu()
35.     {
36.         if (_verticesBuffer == null || _verticesBuffer.count != vertices.Length)
37.         {
38.             if (_verticesBuffer != null)
39.             {
40.                 _verticesBuffer.Release();
41.                 _verticesBuffer = null;
42.             }
43.  
44.             _verticesBuffer = new ComputeBuffer(vertices.Length, 4*4);
45.             triangleMaterial.SetBuffer(verticesBuffer, _verticesBuffer);
46.         }
47.  
48.         _verticesBuffer.SetData(vertices, 0, 0, vertices.Length);
49.     }
50.  
51.     internal void Render()
52.     {
53.         CopyFromCpuToGpu();
54.         triangleMaterial.SetPass(0);
55.         Graphics.DrawProceduralNow(MeshTopology.Triangles, vertices.Length);
56.     }
57. }

Spoiler: TriangleShader.shader

Code (CSharp):

1. Shader "BurstDrawTrianglesShader" {
2.     Properties
3.     {
4.     }
5.     SubShader
6.     {
7.         Tags {"RenderType" = "Opaque" "IgnoreProjector" = "True" "RenderPipeline" = "UniversalPipeline" "ShaderModel"="2.0"}
8.         Cull Off
9.  
10.         Pass
11.         {
12.             Name "Unlit"
13.  
14.             HLSLPROGRAM
15.             #pragma exclude_renderers gles gles3 glcore
16.             #pragma target 4.5
17.  
18.             #pragma vertex vert
19.             #pragma fragment frag
20.  
21.  
22.             #include "UnityCG.cginc"
23.  
24.             uniform StructuredBuffer<float4> verticesBuffer;
25.  
26.             struct vtf
27.             {
28.                 float4 vertex : SV_POSITION;
29.                    float4 color : TEXCOORD0;
30.             };
31.  
32.             // color packed into float4.w (1 byte per RGBA channel)
33.             float4 unpack(float i)
34.             {
35.                 return float4(i / 262144.0, i / 4096.0, i / 64.0, i) % 64.0 / 63;
36.             }
37.  
38.             vtf vert(uint vid : SV_VertexID)
39.             {
40.                 vtf output;
41.                 float4 pos = verticesBuffer[vid];
42.                 output.vertex = mul(UNITY_MATRIX_VP, float4(pos.xyz, 1));
43.                 output.color = unpack(pos.w);
44.                 return output;
45.             }
46.  
47.             half4 frag(vtf input) : SV_Target
48.             {
49.                 return input.color;
50.             }
51.             ENDHLSL
52.         }
53.     }
54.     SubShader
55.     {
56.         Pass
57.         {
58.             CGPROGRAM
59.  
60.             #pragma vertex vert
61.             #pragma fragment frag
62.             #pragma multi_compile_fwdbase nolightmap nodirlightmap nodynlightmap novertexlight
63.             #pragma target 4.5
64.  
65.             #include "UnityCG.cginc"
66.  
67.             StructuredBuffer<float4> verticesBuffer;
68.  
69.             struct v2f
70.             {
71.                 float4 pos : SV_POSITION;
72.                 float4 color : TEXCOORD0;
73.             };
74.  
75.             float4 unpack(float i)
76.             {
77.                 return float4(i / 262144.0, i / 4096.0, i / 64.0, i) % 64.0 / 63;
78.             }
79.  
80.             v2f vert(uint vid : SV_VertexID)
81.             {
82.                 v2f o;
83.                 float4 pos = verticesBuffer[vid];
84.                 o.pos = mul(UNITY_MATRIX_VP, float4(pos.xyz, 1));
85.                 o.color = unpack(pos.w);
86.                 return o;
87.             }
88.  
89.             fixed4 frag(v2f i) : SV_Target
90.             {
91.                 return i.color;
92.             }
93.  
94.             ENDCG
95.         }
96.     }
97. }