Spherical Pivot Transformed Distribution initial commit.

com.unity.render-pipelines.high-definition/HDRP/Material/StackLit/StackLit.cs

         {
             PreIntegratedFGD.instance.Build(PreIntegratedFGD.FGDIndex.FGD_GGXAndDisneyDiffuse);
             LTCAreaLight.instance.Build();
+            SPTDistribution.instance.Build();
 
             m_isInit = false;
         }
             PreIntegratedFGD.instance.Cleanup(PreIntegratedFGD.FGDIndex.FGD_GGXAndDisneyDiffuse);
             LTCAreaLight.instance.Cleanup();
+            SPTDistribution.instance.Cleanup();
 
             m_isInit = false;
         }
         {
             PreIntegratedFGD.instance.Bind(PreIntegratedFGD.FGDIndex.FGD_GGXAndDisneyDiffuse);
             LTCAreaLight.instance.Bind();
+            SPTDistribution.instance.Bind();
         }
     }
 }

com.unity.render-pipelines.high-definition/HDRP/Material/SphericalCapPivot.meta

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com.unity.render-pipelines.high-definition/HDRP/Material/SphericalCapPivot/PivotData.GGX.cs.meta

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com.unity.render-pipelines.high-definition/HDRP/Material/SphericalCapPivot/SPTDistribution.cs

+using System;
+using UnityEngine.Rendering;
+
+namespace UnityEngine.Experimental.Rendering.HDPipeline
+{
+    public partial class SPTDistribution
+    {
+        static SPTDistribution s_Instance;
+
+        public static SPTDistribution instance
+        {
+            get
+            {
+                if (s_Instance == null)
+                    s_Instance = new SPTDistribution();
+
+                return s_Instance;
+            }
+        }
+
+        int m_refCounting;
+
+        Texture2D m_PivotData;
+
+        const int k_PivotLUTResolution = 64;
+        const int k_PivotLUTEntryDim = 4; // the s_PivotLUTData array has 4 components for each entry, we only upload and use first 2
+
+        SPTDistribution()
+        {
+            m_refCounting = 0;
+        }
+
+        // Load LUT data in texture
+        void LoadLUT(Texture2D tex, double[,] PivotData)
+        {
+            const int count = k_PivotLUTResolution * k_PivotLUTResolution;
+            Color[] pixels = new Color[count];
+
+            for (int i = 0; i < count; i++)
+            {
+                pixels[i] = new Color((float)PivotData[i, 0], (float)PivotData[i, 1], 0.0f, 0.0f);
+            }
+
+            tex.SetPixels(pixels);
+        }
+
+        public void Build()
+        {
+            Debug.Assert(m_refCounting >= 0);
+
+            if (m_refCounting == 0)
+            {
+                m_PivotData = new Texture2D(k_PivotLUTResolution, k_PivotLUTResolution, TextureFormat.RGHalf, false /*mipmap*/, true /* linear */)
+                {
+                    hideFlags = HideFlags.HideAndDontSave,
+                    wrapMode = TextureWrapMode.Clamp,
+                    filterMode = FilterMode.Bilinear,
+                    name = CoreUtils.GetTextureAutoName(k_PivotLUTResolution, k_PivotLUTResolution, TextureFormat.RGHalf, depth: 0, dim: TextureDimension.Tex2D, name: "PIVOT_LUT")
+                };
+
+                LoadLUT(m_PivotData, s_PivotLUTData);
+
+                m_PivotData.Apply();
+            }
+
+            m_refCounting++;
+        }
+
+        public void Cleanup()
+        {
+            m_refCounting--;
+
+            if (m_refCounting == 0)
+            {
+                CoreUtils.Destroy(m_PivotData);
+            }
+
+            Debug.Assert(m_refCounting >= 0);
+        }
+
+        public void Bind()
+        {
+            Shader.SetGlobalTexture("_PivotData", m_PivotData);
+        }
+    }
+}

com.unity.render-pipelines.high-definition/HDRP/Material/SphericalCapPivot/SPTDistribution.cs.meta

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com.unity.render-pipelines.high-definition/HDRP/Material/SphericalCapPivot/SPTDistribution.hlsl

+// SPTD: Spherical Pivot Transformed Distributions
+// Keep in synch with the c# side (eg in Bind() and for dims)
+TEXTURE2D_ARRAY(_PivotData);
+
+#define PIVOT_LUT_SIZE   64
+#define PIVOT_LUT_SCALE  ((PIVOT_LUT_SIZE - 1) * rcp(PIVOT_LUT_SIZE))
+#define PIVOT_LUT_OFFSET (0.5 * rcp(PIVOT_LUT_SIZE))

com.unity.render-pipelines.high-definition/HDRP/Material/SphericalCapPivot/SPTDistribution.hlsl.meta

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