Rewrote triplanar to work with the Sampler Asset (some master node issue where Texture2D would fail with no errors). Graphs which don't seem to work should have TriPlanar, SamplerAsset, and TextureAsset deleted and re-added.

MaterialGraphProject/Assets/Eduardo/FunctionNInNOut.cs

             else
                 nextSlotId = GetInputSlots<MaterialSlot>().Count() + 1;
 
-            bool useDefaultValue = (valueType != SlotValueType.Texture2D);
+            bool useDefaultValue = (valueType != SlotValueType.Texture2D && valueType != SlotValueType.Sampler2D);
             AddSlot(new MaterialSlot(nextSlotId, displayName, nameInShader, slotType, valueType, defaultValue, useDefaultValue));
             return nextSlotId;
         }
 
                 if (FindSlot<MaterialSlot>(inSlot.id).concreteValueType != ConcreteSlotValueType.Texture2D
                     && FindSlot<MaterialSlot>(inSlot.id).concreteValueType != ConcreteSlotValueType.SamplerState
+                    && FindSlot<MaterialSlot>(inSlot.id).concreteValueType != ConcreteSlotValueType.Sampler2D
                     )
                     param += precision;
                 param += GetSlotTypeName(inSlot.id) + " ";

MaterialGraphProject/Assets/Vlad/UVTriPlanar.cs

         private string slot0Name = "texRef";
         private string slot1Name = "tileFactor";
         private string slot2Name = "blendFactor";
+        private string slot4Name = "normalRef";
+        private string slot5Name = "posRef";
+        private string slot6Name = "outputRef";
+
+        protected override string GetFunctionName()
+        {
+            return "unity_triplanar_" + precision;
+        }
+
+        public UVTriPlanar()
+        {
+            name = "UVTriPlanar";
+
+            slot0 = AddSlot("Texture", slot0Name, Graphing.SlotType.Input, SlotValueType.Sampler2D, Vector4.zero);
+            slot1 = AddSlot("Tile", slot1Name, Graphing.SlotType.Input, SlotValueType.Vector1, Vector4.zero);
+            slot2 = AddSlot("Blend", slot2Name, Graphing.SlotType.Input, SlotValueType.Vector1, Vector4.zero);
+            slot4 = AddSlot("Normals", slot4Name, Graphing.SlotType.Input, SlotValueType.Vector3, Vector3.one);
+            slot5 = AddSlot("Position", slot5Name, Graphing.SlotType.Input, SlotValueType.Vector3, Vector3.one);
+            slot6 = AddSlot("RGBA ", slot6Name, Graphing.SlotType.Output, SlotValueType.Vector4, Vector4.zero);
+
+            UpdateNodeAfterDeserialization();
+        }
+
+        public override bool hasPreview
+        {
+            get { return true; }
+        }
+
+        public override PreviewMode previewMode
+        {
+            get
+            {
+                return PreviewMode.Preview3D;
+            }
+        }
+
+
+
+        //TODO:Externalize
+        //Reference code from:http://www.chilliant.com/rgb2hsv.html
+        public void GenerateNodeFunction(ShaderGenerator visitor, GenerationMode generationMode)
+        {
+            var outputString = new ShaderGenerator();
+
+            // outputString.AddShaderChunk(GetFunctionPrototype("arg1", "arg2", "arg3", samplerName), false);
+            outputString.AddShaderChunk(GetFunctionPrototype(), false);
+            outputString.Indent();
+            outputString.AddShaderChunk("{", false);
+            // create UVs from position
+            outputString.AddShaderChunk("float3 uvs = " + slot5Name + "*" + slot1Name + ";", false);
+
+            // use absolute value of normal as texture weights
+            outputString.AddShaderChunk("half3 blend = pow(abs(" + slot4Name + ")," + slot2Name + ");", false);
+
+            // make sure the weights sum up to 1 (divide by sum of x+y+z)
+            outputString.AddShaderChunk("blend /= dot(blend, 1.0);", false);
+
+            // read the three texture projections, for x,y,z axes
+            outputString.AddShaderChunk("float4 cx = " + "tex2D(" + slot0Name + ", uvs.yz);", false);
+            outputString.AddShaderChunk("float4 cy = " + "tex2D(" + slot0Name + ", uvs.xz);", false);
+            outputString.AddShaderChunk("float4 cz = " + "tex2D(" + slot0Name + ", uvs.xy);", false);
+
+            // blend the textures based on weights
+            outputString.AddShaderChunk(slot6Name + " = cx * blend.x + cy * blend.y + cz * blend.z;", false);
+
+            outputString.Deindent();
+            outputString.AddShaderChunk("}", false);
+            visitor.AddShaderChunk(outputString.GetShaderString(0), true);
+        }
+
+      
+
+
+        //prevent validation errors when a sampler2D input is missing
+        //use on any input requiring a TextureAssetNode
+        public override void ValidateNode()
+        {
+            base.ValidateNode();
+            var slot = FindInputSlot<MaterialSlot>(0);
+            if (slot == null)
+                return;
+
+            var edges = owner.GetEdges(slot.slotReference).ToList();
+            hasError |= edges.Count == 0;
+        }
+
+        public bool RequiresNormal()
+        {
+            return true;
+        }
+
+        public bool RequiresWorldPosition()
+        {
+            return true;
+        }
+    }
+}
+
+///////////////// TEXTURE2D version below. Works fine, but the master nodes don't jive with it //////////////////////////
+
+
+/*
+
+namespace UnityEngine.MaterialGraph
+{
+    [Title("UV/Tri-Planar Mapping")]
+    public class UVTriPlanar : FunctionNInNOut, IGeneratesFunction, IMayRequireNormal, IMayRequireWorldPosition
+    {
+        private int slot0, slot1, slot2, slot3, slot4, slot5, slot6 = 0;
+
+        private string slot0Name = "texRef";
+        private string slot1Name = "tileFactor";
+        private string slot2Name = "blendFactor";
         private string slot3Name = "samplerRef";
         private string slot4Name = "normalRef";
         private string slot5Name = "posRef";
         }
     }
 }
+ 
+*/