Merge pull request #888 from Unity-Technologies/LW-ScreenSpaceShadows-WPositionReconstruction

Lw screen space shadows w position reconstruction

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightConstantBuffer.cs

         public static int _ShadowOffset2;
         public static int _ShadowOffset3;
         public static int _ShadowmapSize;
-        public static int _FrustumCorners;
     }
 }

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipeline.cs

             ShadowConstantBuffer._ShadowOffset2 = Shader.PropertyToID("_ShadowOffset2");
             ShadowConstantBuffer._ShadowOffset3 = Shader.PropertyToID("_ShadowOffset3");
             ShadowConstantBuffer._ShadowmapSize = Shader.PropertyToID("_ShadowmapSize");
-            ShadowConstantBuffer._FrustumCorners = Shader.PropertyToID("_FrustumCorners");
 
             m_ShadowMapRTID = Shader.PropertyToID("_ShadowMap");
             m_ScreenSpaceShadowMapRTID = Shader.PropertyToID("_ScreenSpaceShadowMap");
             cmd.SetGlobalVector(ShadowConstantBuffer._ShadowOffset2, new Vector4(-invHalfShadowResolution, invHalfShadowResolution, 0.0f, 0.0f));
             cmd.SetGlobalVector(ShadowConstantBuffer._ShadowOffset3, new Vector4(invHalfShadowResolution, invHalfShadowResolution, 0.0f, 0.0f));
             cmd.SetGlobalVector(ShadowConstantBuffer._ShadowmapSize, new Vector4(invShadowResolution, invShadowResolution, m_Asset.ShadowAtlasResolution, m_Asset.ShadowAtlasResolution));
-            cmd.SetGlobalVectorArray(ShadowConstantBuffer._FrustumCorners, LightweightUtils.GetFarPlaneCorners(m_CurrCamera));
         }
 
         private void SetShaderKeywords(CommandBuffer cmd, ref LightData lightData, List<VisibleLight> visibleLights)

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipelineUtils.cs

             // Remaining light types don't support cookies
         }
 
-        public static Vector4[] GetFarPlaneCorners(Camera camera)
-        {
-            Vector4[] corners = new Vector4[4];
-
-            float farH   = 2.0f * Mathf.Tan(camera.fieldOfView * 0.5f * Mathf.Deg2Rad) * camera.farClipPlane;
-            float farW   = farH * camera.aspect;
-            
-            Vector3 fc    = Vector3.forward * camera.farClipPlane;
-            Vector3 up    = Vector3.up; 
-            Vector3 right = Vector3.right; 
-
-            corners[0] = fc - (up * farH / 2) - (right * farW / 2);
-            corners[1] = fc + (up * farH / 2) - (right * farW / 2);
-            corners[2] = fc + (up * farH / 2) + (right * farW / 2);
-            corners[3] = fc - (up * farH / 2) + (right * farW / 2);
-
-            return corners;
-        }
-
         public static bool IsSupportedShadowType(LightType lightType)
         {
             return lightType == LightType.Directional || lightType == LightType.Spot;

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/Shadows.hlsl

 half4       _ShadowOffset3;
 half4       _ShadowData;    // (x: shadowStrength)
 float4      _ShadowmapSize; // (xy: 1/width and 1/height, zw: width and height)
-float4      _FrustumCorners[4];
 CBUFFER_END
 
 #if UNITY_REVERSED_Z

ScriptableRenderPipeline/LightweightPipeline/LWRP/Shaders/LightweightScreenSpaceShadows.shader

 
         struct VertexInput
         {
-            float4 vertex : POSITION;
-            float2 uv     : TEXCOORD0;
-            uint   id     : SV_VertexID;
+            float4 vertex   : POSITION;
+            float2 texcoord : TEXCOORD0;
-            half4  pos          : SV_POSITION;
-            half2  uv           : TEXCOORD0;
-            
-            //Perspective Case
-            float3 ray          : TEXCOORD1;
-
-            //Orthographic Case
-            float3 orthoPosNear : TEXCOORD2;
-            float3 orthoPosFar  : TEXCOORD3;
-            
+            half4  pos      : SV_POSITION;
+            half4  texcoord : TEXCOORD0;
-        float3 ComputeViewSpacePositionGeometric(Interpolators i)
-        {
-            float zDepth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, sampler_CameraDepthTexture, i.uv);
-            float depth  = Linear01Depth(zDepth, _ZBufferParams);
-
-        #if UNITY_REVERSED_Z
-            zDepth = 1 - zDepth;
-        #endif
-
-            //Perspective Case
-            float3 vposPersp = i.ray * depth;
-
-            //Orthographics Case
-            float3 vposOrtho = lerp(i.orthoPosNear, i.orthoPosFar, zDepth);
-
-            return lerp(vposPersp, vposOrtho, unity_OrthoParams.w);
-        }
-
         Interpolators Vertex(VertexInput i)
         {
             Interpolators o;
             o.pos = TransformObjectToHClip(i.vertex.xyz);
-            o.uv  = i.uv;
-            //Perspective Case
-            o.ray = _FrustumCorners[i.id].xyz; 
+            float4 projPos = o.pos * 0.5;
+            projPos.xy = projPos.xy + projPos.w;
-            //Orthographic Case
-            float4 clipPos = o.pos;
-            clipPos.y *= _ProjectionParams.x;
-            float3 orthoPosNear = mul(unity_CameraInvProjection, float4(clipPos.x, clipPos.y, -1, 1)).xyz;
-            float3 orthoPosFar  = mul(unity_CameraInvProjection, float4(clipPos.x, clipPos.y,  1, 1)).xyz;
-            orthoPosNear.z *= -1;
-            orthoPosFar.z  *= -1;
-            o.orthoPosNear = orthoPosNear;
-            o.orthoPosFar  = orthoPosFar;
+            o.texcoord.xy = i.texcoord;
+            o.texcoord.zw = projPos.xy;
 
             return o;
         }
             UNITY_SETUP_INSTANCE_ID(i);
 
-            //Reconstruct the world position.
-            float3 vpos = ComputeViewSpacePositionGeometric(i); //TODO: Profile against unprojection method in core library.
+            float deviceDepth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, sampler_CameraDepthTexture, i.texcoord.xy);
+
+#if UNITY_REVERSED_Z
+            deviceDepth = 1 - deviceDepth;
+#endif
+            deviceDepth = 2 * deviceDepth - 1; //NOTE: Currently must massage depth before computing CS position. 
+
+            float3 vpos = ComputeViewSpacePosition(i.texcoord.zw, deviceDepth, unity_CameraInvProjection);
-            //Fetch shadow coordinates.
+            //Fetch shadow coordinates for cascade.
             float4 coords  = ComputeShadowCoord(wpos);
 
             return SampleShadowmap(coords);