[shader graph] add lerp node.

UnityProject/Assets/UnityShaderEditor/Editor/Source/Nodes/LerpNode.cs

+namespace UnityEditor.Graphs.Material
+{
+    [Title("Math/Lerp Node")]
+    class LerpNode : Function3Input, IGeneratesFunction
+    {
+        public override void Init()
+        {
+            name = "LerpNode";
+            base.Init();
+        }
+
+        protected override string GetFunctionName() {return "unity_lerp_" + precision; }
+
+        public void GenerateNodeFunction(ShaderGenerator visitor, GenerationMode generationMode)
+        {
+            var outputString = new ShaderGenerator();
+            foreach (var precision in m_PrecisionNames)
+            {
+                outputString.AddShaderChunk("inline " + precision + "4 unity_lerp_" + precision + " (" + precision + "4 first, " + precision + "4 second, " + precision + "4 s)", false);
+                outputString.AddShaderChunk("{", false);
+                outputString.Indent();
+                outputString.AddShaderChunk("return lerp(first, second, s);", false);
+                outputString.Deindent();
+                outputString.AddShaderChunk("}", false);
+            }
+
+            visitor.AddShaderChunk(outputString.GetShaderString(0), true);
+        }
+    }
+}

UnityProject/Assets/UnityShaderEditor/Editor/Source/Nodes/LerpNode.cs.meta

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+licenseType: Pro
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