Add alpha clip threshold to PRB master.

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/LightweightPipeline/LightWeightPBRSubShader.cs

                 PBRMasterNode.MetallicSlotId,
                 PBRMasterNode.SmoothnessSlotId,
                 PBRMasterNode.OcclusionSlotId,
-                PBRMasterNode.AlphaSlotId
+                PBRMasterNode.AlphaSlotId,
+                PBRMasterNode.AlphaThresholdSlotId
             }
         };
 
                 PBRMasterNode.SpecularSlotId,
                 PBRMasterNode.SmoothnessSlotId,
                 PBRMasterNode.OcclusionSlotId,
-                PBRMasterNode.AlphaSlotId
+                PBRMasterNode.AlphaSlotId,
+                PBRMasterNode.AlphaThresholdSlotId
             }
         };
 
                 case PBRMasterNode.AlphaMode.AdditiveBlend:
                     defines.AddShaderChunk("#define _AlphaOut 1", true);
                     break;
-                case PBRMasterNode.AlphaMode.Clip:
-                    defines.AddShaderChunk("#define _AlphaClip 1", true);
-                    break;
+            if (masterNode.IsSlotConnected(PBRMasterNode.AlphaThresholdSlotId))
+                defines.AddShaderChunk("#define _AlphaClip 1", true);
+
-                surfaceOutputRemap.AddShaderChunk(slot.shaderOutputName
-                    + " = surf."
-                    + slot.shaderOutputName + ";", true);
+                surfaceOutputRemap.AddShaderChunk(string.Format("{0} = surf.{0};", slot.shaderOutputName), true);
             }
 
             if (!File.Exists(templateLocation))
             var materialOptions = new SurfaceMaterialOptions();
             switch (masterNode.alphaMode)
             {
-                case PBRMasterNode.AlphaMode.Overwrite:
-                case PBRMasterNode.AlphaMode.Clip:
+                case PBRMasterNode.AlphaMode.Opaque:
                     materialOptions.srcBlend = SurfaceMaterialOptions.BlendMode.One;
                     materialOptions.dstBlend = SurfaceMaterialOptions.BlendMode.Zero;
                     materialOptions.cullMode = SurfaceMaterialOptions.CullMode.Back;

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/MasterNodes/PBRMasterNode.cs

         public const string SmoothnessSlotName = "Smoothness";
         public const string OcclusionSlotName = "Occlusion";
         public const string AlphaSlotName = "Alpha";
+        public const string AlphaClipThresholdSlotName = "AlphaClipThreshold";
         public const string VertexOffsetName = "VertexPosition";
 
         public const int AlbedoSlotId = 0;
         public const int SmoothnessSlotId = 5;
         public const int OcclusionSlotId = 6;
         public const int AlphaSlotId = 7;
+        public const int AlphaThresholdSlotId = 8;
 
         public enum Model
         {
 
         public enum AlphaMode
         {
-            Overwrite,
+            Opaque,
-            AdditiveBlend,
-            Clip
+            AdditiveBlend
         }
 
         [SerializeField]
             AddSlot(new Vector1MaterialSlot(SmoothnessSlotId, SmoothnessSlotName, SmoothnessSlotName, SlotType.Input, 0.5f, ShaderStage.Fragment));
             AddSlot(new Vector1MaterialSlot(OcclusionSlotId, OcclusionSlotName, OcclusionSlotName, SlotType.Input, 1f, ShaderStage.Fragment));
             AddSlot(new Vector1MaterialSlot(AlphaSlotId, AlphaSlotName, AlphaSlotName, SlotType.Input, 1f, ShaderStage.Fragment));
+            AddSlot(new Vector1MaterialSlot(AlphaThresholdSlotId, AlphaClipThresholdSlotName, AlphaClipThresholdSlotName, SlotType.Input, 0f, ShaderStage.Fragment));
 
             // clear out slot names that do not match the slots
             // we support
                 model == Model.Metallic ? MetallicSlotId : SpecularSlotId,
                 SmoothnessSlotId,
                 OcclusionSlotId,
-                AlphaSlotId
+                AlphaSlotId,
+                AlphaThresholdSlotId
             });
         }
 

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Templates/lightweightPBRForwardPass.template

 		float Smoothness = 0.5;
 		float Occlusion = 1;
 		float Alpha = 1;
+		float AlphaClipThreshold = 0;
 
         ${SurfaceOutputRemap}
 
 #endif
 
 #if _AlphaClip
-		clip(Alpha - 0.01);
+		clip(Alpha - AlphaClipThreshold);
 #endif
 		return color;
     }