Using surface shader with compute buffers

gistfile1.txt

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Custom/CS_GeneratedMesh_VertexID_Surf" 
{
	Properties 
	{
		_Color ("Color", Color) = (1,1,1,1)
		_MainTex ("Albedo (RGB)", 2D) = "white" {}
		_Glossiness("Smoothness", Range(0,1)) = 0.5
		_Metallic("Metallic", Range(0,1)) = 0.0

		_SpawnColAudioColMix("Spawn Col vs Audio Col Mix", Range(0,1)) = 1.0
		_TextureScaleX("TextureScale X", Range(0,1)) = 1.0
		_TextureScaleY("TextureScale Y", Range(0,1)) = 1.0

		_SimSpeed("Sim Speed", float) = 1

		_GeneratedMesh_VertexCount("_Generated Mesh Vertex Count", int) = 24 // 24 for unity default cube
		_GeneratedMesh_BaseScaler("Generated Mesh Base Scaler", Range(0,10)) = 1.0
		_GeneratedMesh_YScaler("Generated Mesh Y Scaler", Range(0,1)) = 1.0

		_SpawnColorScaler("Spawn Color Scaler", Range(0,4)) = 1.0
		_LiveAudioColorScaler("Live Audio Scaler", Range(0,4)) = 1.0
		_FinalColorScaler("Final Color Scaler", Range(0,4)) = 1.0
	}
	SubShader 
	{
		Tags { "RenderType"="Opaque" }
		LOD 200
		
		//Cull Off

		CGPROGRAM
		// Physically based Standard lighting model, and enable shadows on all light types
		//#pragma surface surf Standard fullforwardshadows vertex:vert
		#pragma surface surf Standard addshadow vertex:vert	
		//#pragma multi_compile_instancing

		#pragma target 5.0

		#include "UnityCG.cginc"

		#ifdef SHADER_API_D3D11		

		StructuredBuffer<float4> _Positions;
		StructuredBuffer<float4> _Colors;
		StructuredBuffer<float4> _Velocities;
		StructuredBuffer<float4> _ForwardVectors;
		StructuredBuffer<float4> _UpVectors;
		StructuredBuffer<uint> _ParticlesToSpawnIDs; // bad name, should be ToDraw

		#endif


		sampler2D _MainTex;
		half _SpawnColAudioColMix;
		half _TextureScaleX;
		half _TextureScaleY;

		half _SimSpeed;
				
		int _GeneratedMesh_VertexCount;
		half _GeneratedMesh_BaseScaler;

		half _SpawnColorScaler;
		half _LiveAudioColorScaler;
		half _FinalColorScaler;
		half _GeneratedMesh_YScaler;

		// struct for vertex input data
		struct appdata_id
		{
			float4 vertex : POSITION;
			float3 normal : NORMAL;
			float4 texcoord : TEXCOORD0;
			uint id : SV_VertexID;
		};

		struct Input 
		{
			float2 uv_MainTex;
			float4 col;
		};


		void vert(inout appdata_id v, out Input o)
		{
			float3 vertexPos = v.vertex.xyz;

			UNITY_INITIALIZE_OUTPUT(Input, o);

			
			
			#ifdef SHADER_API_D3D11		

			// setup base data 
			int meshID = v.id / _GeneratedMesh_VertexCount;
			uint particleID = _ParticlesToSpawnIDs[(uint)meshID];
			float4 posData = _Positions[particleID];
			float4 colData = _Colors[particleID];
			float4 velData = _Velocities[particleID];			
			float4 upVecData = _UpVectors[particleID];			
			float3 particleWorldPos = posData.xyz;
			float speed = length(velData.xyz);

			// calcualte particle life and scale
			float lifeRemaining = max(0, posData.w);
			float maxLife = upVecData.w;
			float lifeRatio = min((lifeRemaining / maxLife), 1);
			float spriteScale = lifeRatio * velData.w;
			
			// calculate particle color			
			float2 audioColUV = float2(_TextureScaleX, _TextureScaleY * (1.0 - lifeRatio)); //+ IN.idOffset));
			float lifeColScaler = 1.0; //max((lifeRatio + 0.17), 0.5);
			float4 audioCol = lifeColScaler * tex2Dlod(_MainTex, float4(audioColUV, 0, 0));
			float4 spawnedCol = colData;
			//float4 mixedCol = lerp(spawnedCol * _SpawnColorScaler, audioCol * _LiveAudioColorScaler, _SpawnColAudioColMix);
			float4 mixedCol = spawnedCol * _SpawnColorScaler +  pow((0.50 + audioCol * _LiveAudioColorScaler), 2) * _SpawnColAudioColMix;
			o.col = mixedCol;

			// calculate particle rotaiton
			float3 normedVel = normalize(velData).xyz;			
			float3 pDir = normedVel;
			//pDir = float3(0, 0, 1);
			float3 upDir = upVecData.xyz; //float3(0, 1, 0);	
			//upDir = float3(0, 1, 0);
			// tried, got this from http://stackoverflow.com/questions/18558910/direction-vector-to-rotation-matrix
			float3 xAxis = normalize(cross(upDir, pDir));
			float3 yAxis = normalize(cross(pDir, xAxis));
			matrix forwardRotMat = matrix(	xAxis.x, yAxis.x, pDir.x, 0,
											xAxis.y, yAxis.y, pDir.y, 0,
											xAxis.z, yAxis.z, pDir.z, 0,
											0, 0, 0, 1);




			// speed boost scale
			vertexPos.y *= _GeneratedMesh_YScaler;
			vertexPos.z *= pow(1.0 + abs(0.5*speed) * abs(0.5*_SimSpeed), 2);

			

			// set particle scale
			// apply base mesh scaling
			vertexPos *= _GeneratedMesh_BaseScaler; // scale
			vertexPos *= spriteScale;
			// set particle world pos
			//vertexPos = particleWorldPos + mul(UNITY_MATRIX_VP, mul(forwardRotMat, vertexPos)) ;
			//vertexPos = particleWorldPos + vertexPos;
			//vertexPos += particleWorldPos;

			vertexPos = mul(forwardRotMat, vertexPos);
			vertexPos += particleWorldPos ;

			v.normal = mul(forwardRotMat, v.normal);

			#endif

			//v.vertex.xyz = mul( transpose(UNITY_MATRIX_VP), vertexPos);
			v.vertex.xyz = vertexPos;
		}

		half _Glossiness;
		half _Metallic;
		fixed4 _Color;

		// Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
		// See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
		// #pragma instancing_options assumeuniformscaling
		UNITY_INSTANCING_BUFFER_START(Props)
			// put more per-instance properties here
		UNITY_INSTANCING_BUFFER_END(Props)

		void surf (Input IN, inout SurfaceOutputStandard o) 
		{
			// Albedo comes from a texture tinted by color
			fixed4 c = IN.col; //tex2D (_MainTex, IN.uv_MainTex) * _Color;
			//c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
						
			o.Albedo = c.rgb * _FinalColorScaler;
			// Metallic and smoothness come from slider variables
			o.Metallic = _Metallic;
			o.Smoothness = _Glossiness;
			o.Alpha = c.a;

			
		}
		ENDCG
	}
	FallBack "Diffuse"
}