Remove redundant matrix multiplication in voxelization step

Author: Looooong

CHANGELOG.md

@@ -15,6 +15,7 @@
 
 - Improved cone tracing direction selection.
 - Removed cone tracing bias.
+- Removed redundant matrix multiplication in voxelization step.
 
 ### Fixed
 

Resources/VXGI/Compute/VoxelShader.compute

@@ -81,6 +81,8 @@ void CSRender(uint id : SV_DispatchThreadID)
 
   uint4 intColor = (uint4)round(color * RADIANCE_PRECISION);
 
+  position = min(position, Resolution - 1);
+
   InterlockedAdd(RadianceRG[position], intColor.r | intColor.g << 16);
   InterlockedAdd(RadianceBA[position], intColor.b | intColor.a << 16);
   InterlockedAdd(RadianceCount[position], 1);

Runtime/Stages/Voxelizer.cs

@@ -4,12 +4,10 @@
 public class Voxelizer : System.IDisposable {
   int _antiAliasing;
   int _resolution;
-  float _bound;
   Camera _camera;
   CommandBuffer _command;
   DrawingSettings _drawingSettings;
   FilteringSettings _filteringSettings;
-  Rect _rect;
   RenderTextureDescriptor _cameraDescriptor;
   ScriptableCullingParameters _cullingParameters;
   VXGI _vxgi;
@@ -18,7 +16,6 @@ public Voxelizer(VXGI vxgi) {
     _vxgi = vxgi;
 
     _command = new CommandBuffer { name = "VXGI.Voxelizer" };
-    _rect = new Rect(0f, 0f, 1f, 1f);
 
     CreateCamera();
     CreateCameraDescriptor();
@@ -51,17 +48,14 @@ public void Voxelize(ScriptableRenderContext renderContext, VXGIRenderer rendere
 
     UpdateCamera();
 
-    _camera.pixelRect = _rect;
-
     _command.BeginSample(_command.name);
 
     _command.GetTemporaryRT(ShaderIDs.Dummy, _cameraDescriptor);
     _command.SetRenderTarget(ShaderIDs.Dummy, RenderBufferLoadAction.DontCare, RenderBufferStoreAction.DontCare);
 
     _command.SetGlobalInt(ShaderIDs.Resolution, _resolution);
-    _command.SetGlobalMatrix(ShaderIDs.WorldToVoxel, _vxgi.worldToVoxel);
-    _command.SetGlobalMatrix(ShaderIDs.VoxelToProjection, GL.GetGPUProjectionMatrix(_camera.projectionMatrix, true) * _camera.worldToCameraMatrix * _vxgi.voxelToWorld);
     _command.SetRandomWriteTarget(1, _vxgi.voxelBuffer, false);
+    _command.SetViewProjectionMatrices(_camera.worldToCameraMatrix, _camera.projectionMatrix);
 
     _drawingSettings.perObjectData = renderer.RenderPipeline.PerObjectData;
 
@@ -87,7 +81,7 @@ void CreateCamera() {
     _camera = gameObject.AddComponent<Camera>();
     _camera.allowMSAA = true;
     _camera.orthographic = true;
-    _camera.nearClipPlane = 0f;
+    _camera.pixelRect = new Rect(0f, 0f, 1f, 1f);
   }
 
   void CreateCameraDescriptor() {
@@ -106,28 +100,20 @@ void CreateCameraSettings() {
     _filteringSettings = new FilteringSettings(RenderQueueRange.all);
   }
 
-  void ResizeCamera() {
-    _camera.farClipPlane = _bound;
-    _camera.orthographicSize = .5f * _camera.farClipPlane;
-  }
-
   void UpdateCamera() {
     if (_antiAliasing != (int)_vxgi.antiAliasing) {
       _antiAliasing = (int)_vxgi.antiAliasing;
       _cameraDescriptor.msaaSamples = _antiAliasing;
     }
 
-    if (_bound != _vxgi.bound) {
-      _bound = _vxgi.bound;
-      ResizeCamera();
-    }
-
     if (_resolution != (int)_vxgi.resolution) {
       _resolution = (int)_vxgi.resolution;
       _cameraDescriptor.height = _cameraDescriptor.width = _resolution;
     }
 
-    _camera.transform.position = _vxgi.voxelSpaceCenter - Vector3.forward * _camera.orthographicSize;
-    _camera.transform.LookAt(_vxgi.voxelSpaceCenter, Vector3.up);
+    _camera.farClipPlane = .5f * _vxgi.bound;
+    _camera.orthographicSize = .5f * _vxgi.bound;
+    _camera.nearClipPlane = -.5f * _vxgi.bound;
+    _camera.transform.position = _vxgi.voxelSpaceCenter;
   }
 }

Runtime/Utilities/ShaderIDs.cs

@@ -43,7 +43,6 @@ internal static class ShaderIDs {
   internal static readonly int Source = Shader.PropertyToID("Source");
   internal static readonly int Target = Shader.PropertyToID("Target");
   internal static readonly int VoxelBuffer = Shader.PropertyToID("VoxelBuffer");
-  internal static readonly int VoxelToProjection = Shader.PropertyToID("VoxelToProjection");
   internal static readonly int VoxelToWorld = Shader.PropertyToID("VoxelToWorld");
   internal static readonly int WorldToVoxel = Shader.PropertyToID("WorldToVoxel");
 }

Runtime/VXGI.cs

@@ -188,7 +188,7 @@ void SetupShader(ScriptableRenderContext renderContext) {
 
   #region Messages
   void OnDrawGizmosSelected() {
-    Gizmos.color = new Color(0, 0, 1, .2f);
+    Gizmos.color = Color.green;
     Gizmos.DrawWireCube(voxelSpaceCenter, Vector3.one * bound);
   }
 

Shaders/Voxelization.shader

@@ -8,8 +8,8 @@ Shader "Hidden/VXGI/Voxelization"
       Tags { "LightMode"="Voxelization" }
 
       Cull Off
-      ZWrite Off
       ZTest Always
+      ZWrite Off
 
       HLSLPROGRAM
       #pragma require geometry
@@ -18,6 +18,7 @@ Shader "Hidden/VXGI/Voxelization"
       #pragma geometry geom
       #pragma fragment frag
       #pragma shader_feature _EMISSION
+      #pragma shader_feature_local _METALLICGLOSSMAP
 
       #include "UnityCG.cginc"
       #include "Packages/com.looooong.srp.vxgi/ShaderLibrary/Variables.cginc"
@@ -29,18 +30,14 @@ Shader "Hidden/VXGI/Voxelization"
 
       CBUFFER_START(UnityPerMaterial)
         half4 _Color;
+        half3 _EmissionColor;
         float4 _MainTex_ST;
         half _Metallic;
-        half3 _EmissionColor;
       CBUFFER_END
 
+      sampler2D _EmissionMap;
       sampler2D _MainTex;
       sampler2D _MetallicGlossMap;
-      sampler2D _EmissionMap;
-
-      // Map depth [0, 1] to Z coordinate [0, Resolution)
-      static float DepthResolution = Resolution * 0.99999999;
-      float4x4 VoxelToProjection;
 
       AppendStructuredBuffer<VoxelData> VoxelBuffer;
 
@@ -62,9 +59,14 @@ Shader "Hidden/VXGI/Voxelization"
       v2g vert(appdata_base v)
       {
         v2g o;
-        o.vertex = mul(WorldToVoxel, mul(unity_ObjectToWorld, v.vertex));
+        o.vertex = UnityObjectToClipPos(v.vertex);
         o.normal = UnityObjectToWorldNormal(v.normal);
         o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
+
+#ifdef UNITY_REVERSED_Z
+        o.vertex.z = mad(o.vertex.z, -2.0, 1.0);
+#endif
+
         return o;
       }
 
@@ -107,11 +109,15 @@ Shader "Hidden/VXGI/Voxelization"
         for (int j = 0; j < 3; j++) {
           g2f o;
 
-          o.position = mul(VoxelToProjection, float4(SwizzleAxis(i[j].vertex, axis), 1.0));
+          o.position = float4(SwizzleAxis(i[j].vertex, axis), 1.0);
 
-          #if defined(UNITY_REVERSED_Z)
-            o.position.z = 1.0 - o.position.z;
-          #endif
+#ifdef UNITY_UV_STARTS_AT_TOP
+          o.position.y = -o.position.y;
+#endif
+
+#ifdef UNITY_REVERSED_Z
+          o.position.z = mad(o.position.z, 0.5, 0.5);
+#endif
 
           o.normal = i[j].normal;
           o.axis = axis;
@@ -145,23 +151,25 @@ Shader "Hidden/VXGI/Voxelization"
 
       fixed frag(g2f i) : SV_TARGET
       {
-        #ifdef _METALLICGLOSSMAP
-          float metallic = tex2D(_MetallicGlossMap, i.uv).r;
-        #else
-          float metallic = _Metallic;
-        #endif
+#ifdef _METALLICGLOSSMAP
+        float metallic = tex2D(_MetallicGlossMap, i.uv).r;
+#else
+        float metallic = _Metallic;
+#endif
 
         i.normal = normalize(i.normal);
 
-        #ifdef _EMISSION
-          float3 emission = _EmissionColor * tex2Dlod(_EmissionMap, float4(i.uv, 0.0, 0.0));
-        #else
-          float3 emission = 0.0;
-        #endif
+#ifdef _EMISSION
+        float3 emission = _EmissionColor * tex2Dlod(_EmissionMap, float4(i.uv, 0.0, 0.0));
+#else
+        float3 emission = 0.0;
+#endif
+
+        float3 voxelPosition = float3(i.position.xy, i.position.z * Resolution);
 
         VoxelData d;
         d.Initialize();
-        d.SetPosition(RestoreAxis(float3(i.position.xy, i.position.z * DepthResolution), i.axis));
+        d.SetPosition(RestoreAxis(voxelPosition, i.axis));
         d.SetNormal(i.normal);
         d.SetColor(mad(-0.5, metallic, 1.0) * _Color * tex2Dlod(_MainTex, float4(i.uv, 0.0, 0.0)));
         d.SetEmission(emission + ShadeSH9(float4(i.normal, 1.0)));