Merge pull request #815 from Unity-Technologies/minor-comment/code-on-decal

minor comment/code on decal

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Decal/DecalProjectorComponent.cs

     [ExecuteInEditMode]
     public class DecalProjectorComponent : MonoBehaviour
     {
-        private static readonly int m_WorldToDecal = Shader.PropertyToID("_WorldToDecal");
-        private static readonly int m_DecalToWorldR = Shader.PropertyToID("_DecalToWorldR");
-
         public Material m_Material = null;
         private Material m_OldMaterial = null;
         public const int kInvalidIndex = -1;

ScriptableRenderPipeline/HDRenderPipeline/HDRP/ShaderPass/ShaderPassDBuffer.hlsl

 VaryingsMeshType Transform(AttributesMesh input)
 {
     VaryingsMeshType output;
-	
+
 	UNITY_SETUP_INSTANCE_ID(input)
 	UNITY_TRANSFER_INSTANCE_ID(input, output);
 
 
 	output.positionWS = decalRotation[0];
     output.normalWS = decalRotation[1];
-    output.tangentWS = float4(decalRotation[2], 0); 
+    output.tangentWS = float4(decalRotation[2], 0.0);
 
     return output;
 }
 }
 
 void Frag(  PackedVaryingsToPS packedInput,
-            OUTPUT_DBUFFER(outDBuffer)            
+            OUTPUT_DBUFFER(outDBuffer)
-{	
-
+{
-	float d = LOAD_TEXTURE2D(_MainDepthTexture, posInput.positionSS).x;
-	UpdatePositionInput(d, UNITY_MATRIX_I_VP, UNITY_MATRIX_VP, posInput);
+	float depth = LOAD_TEXTURE2D(_MainDepthTexture, posInput.positionSS).x;
+	UpdatePositionInput(depth, UNITY_MATRIX_I_VP, UNITY_MATRIX_VP, posInput);
+    // Transform from world space to decal space (DS) to clip the decal.
+    // For this we must use absolute position.
+    // There is no lose of precision here as it doesn't involve the camera matrix
-	float3 positionDS = mul(UNITY_MATRIX_I_M, float4(positionWS, 1.0f)).xyz;
-	positionDS = positionDS * float3(1.0f, -1.0f, 1.0f) + float3(0.5f, 0.0f, 0.5f);
-	clip(positionDS < 0 ? -1 : 1);
-	clip(positionDS > 1 ? -1 : 1);
+	float3 positionDS = mul(UNITY_MATRIX_I_M, float4(positionWS, 1.0)).xyz;
+	positionDS = positionDS * float3(1.0, -1.0, 1.0) + float3(0.5, 0.0f, 0.5);
+	clip(positionDS);       // clip negative value
+	clip(1.0 - positionDS); // Clip value above one
 
     DecalSurfaceData surfaceData;
 	float3x3 decalToWorld;