Sample Point Cache operator (#92)

Author: ludovic-theobald

TestProjects/VisualEffectGraph_HDRP/Assets/AllTests/VFXTests/GraphicsTests/09_PointCache.vfx

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [10.3.0] - 2020-11-16
 ### Added
 - Added new setting to output nodes to exclude from TAA
+- New Sample Point cache & Sample Attribute map operators
 
 ### Fixed
 - Forbid incorrect link between incompatible context [Case 1269756](https://issuetracker.unity3d.com/product/unity/issues/guid/1269756/)

TestProjects/VisualEffectGraph_HDRP/Assets/AllTests/VFXTests/GraphicsTests/UnityLogoPrimeCount.pcache

@@ -0,0 +1,28 @@
+using System;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using UnityEngine;
+using UnityEngine.VFX;
+
+namespace UnityEditor.VFX
+{
+    class VFXExpressionSampleAttributeMap<T> : VFXExpression
+    {
+        public VFXExpressionSampleAttributeMap() : this(VFXTexture2DValue.Default, VFXValue<int>.Default, VFXValue<int>.Default)
+        {
+        }
+
+        public VFXExpressionSampleAttributeMap(VFXExpression texture, VFXExpression x, VFXExpression y )
+            : base(Flags.InvalidOnCPU, new VFXExpression[3] { texture, x, y })
+        { }
+
+        sealed public override VFXExpressionOperation operation { get { return VFXExpressionOperation.None; } }
+        sealed public override VFXValueType valueType { get { return VFXExpression.GetVFXValueTypeFromType(typeof(T)); } }
+
+        public sealed override string GetCodeString(string[] parents)
+        {
+            string typeString = VFXExpression.TypeToCode(valueType);
+            return string.Format("({3}){0}.Load(int3({1}, {2}, 0))", parents[0], parents[1], parents[2], typeString);
+        }
+    }
+}