Added Texel Size Node (#1527)

* adding texel size node
* updated changelog

com.unity.shadergraph/CHANGELOG.md

 
 This adds a new node for LOD functionality on a Texture 2D Sample. Sample Texture 2D LOD uses the exact same input and output slots as Sample Texture 2D, but also includes an input for level of detail adjustments via a Vector1 slot. 
 
+### Texel Size Node
+
+![](.data/texel_size_node.png)
+
+With this node, you can get the special texture properties of a Texture 2D Asset via the `{texturename}_TexelSize` variable. Based on input from the Texture 2D Asset, the node outputs the width and height of the texel size in Vector1 format.
+
+**Note:** Do not use the default input to reference your texture Asset. It makes your graph perform worse. Connect this node to a separate Texture 2D Asset node per image example.
+
 ### Show generated code
 
 ![](.data/show_generated_code.gif)

com.unity.shadergraph/Editor/Data/Graphs/TextureShaderProperty.cs

 
         public override string GetPropertyDeclarationString(string delimiter = ";")
         {
-            return string.Format("TEXTURE2D({0}){1} SAMPLER(sampler{0}){1}", referenceName, delimiter);
+            return string.Format("TEXTURE2D({0}){1} SAMPLER(sampler{0}); float4 {0}_TexelSize{1}", referenceName, delimiter);
         }
 
         public override string GetPropertyAsArgumentString()

com.unity.shadergraph/.data/texel_size_node.PNG

+version https://git-lfs.github.com/spec/v1
+oid sha256:7502c3fdf5b201b4460a317b577d4e0490e500a6926ba35c53e236afa15ab76a
+size 82906

com.unity.shadergraph/Editor/Data/Nodes/Input/Texture/TexelSizeNode.cs

+using System.Linq;
+using UnityEngine;
+using UnityEditor.Graphing;
+using UnityEditor.ShaderGraph.Drawing.Controls;
+
+namespace UnityEditor.ShaderGraph
+{
+    
+    [Title("Input", "Texture", "Texel Size")]
+    public class Texture2DPropertiesNode : AbstractMaterialNode, IGeneratesBodyCode, IMayRequireMeshUV
+    {
+        public const int OutputSlotWId = 0;
+        public const int OutputSlotHId = 2;
+        public const int TextureInputId = 1;
+        const string kOutputSlotWName = "Width";
+        const string kOutputSlotHName = "Height";
+        const string kTextureInputName = "Texture";
+
+        public override bool hasPreview { get { return false; } }
+
+        public Texture2DPropertiesNode()
+        {
+            name = "Texel Size";
+            UpdateNodeAfterDeserialization();
+        }
+
+        public override string documentationURL
+        {
+            get { return "https://github.com/Unity-Technologies/ShaderGraph/wiki/Texel-Size-Node"; }
+        }
+
+        public sealed override void UpdateNodeAfterDeserialization()
+        {
+            AddSlot(new Vector1MaterialSlot(OutputSlotWId, kOutputSlotWName, kOutputSlotWName, SlotType.Output, 0, ShaderStageCapability.Fragment));
+            AddSlot(new Vector1MaterialSlot(OutputSlotHId, kOutputSlotHName, kOutputSlotHName, SlotType.Output, 0, ShaderStageCapability.Fragment));
+            AddSlot(new Texture2DInputMaterialSlot(TextureInputId, kTextureInputName, kTextureInputName));
+            RemoveSlotsNameNotMatching(new[] { OutputSlotWId, OutputSlotHId, TextureInputId });
+        }
+
+        // Node generations
+        public virtual void GenerateNodeCode(ShaderGenerator visitor, GenerationMode generationMode)
+        {
+			visitor.AddShaderChunk(string.Format("{0}2 {1} = {2}_TexelSize.z;", precision, GetVariableNameForSlot(OutputSlotWId), GetSlotValue(TextureInputId, generationMode)), true);
+			visitor.AddShaderChunk(string.Format("{0}2 {1} = {2}_TexelSize.w;", precision, GetVariableNameForSlot(OutputSlotHId), GetSlotValue(TextureInputId, generationMode)), true);
+        }
+
+        public bool RequiresMeshUV(UVChannel channel, ShaderStageCapability stageCapability)
+        {
+            return true;
+        }
+    }
+}

com.unity.shadergraph/Editor/Data/Nodes/Input/Texture/TexelSizeNode.cs.meta

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