Small Node Fixes (#1670)

* unroll simple noise loop and add overwrite blend mode to blend node
* updated changelog
* fixed polygon node caluclations
* put overwrite blend mode at the end of the enum
* updates to changelog
* fixing z calculation on normal strength node

com.unity.shadergraph/CHANGELOG.md

 - Texture 2D Array and Texture 3D nodes can no longer be used in the vertex shader.
 - Shader graphs using alpha clip now generate correct depth and shadow passes.
 - `Normal Create` node has been renamed to `Normal From Texture`.
+- `Blend` node now supports Overwrite mode.
+- `Simple Noise` node no longer has a loop.
+- The `Polygon` node now calculates radius based on apothem.
+- `Normal Strength` node now calculates Z value more accurately.

com.unity.shadergraph/Editor/Data/Nodes/Artistic/Blend/BlendMode.cs

         Screen,
         SoftLight,
         Subtract,
-        VividLight
+        VividLight,
+        Overwrite
     }
 }

com.unity.shadergraph/Editor/Data/Nodes/Artistic/Blend/BlendNode.cs

 }
 ";
         }
+        
+        static string Unity_Blend_Overwrite(
+            [Slot(0, Binding.None)] DynamicDimensionVector Base,
+            [Slot(1, Binding.None)] DynamicDimensionVector Blend,
+            [Slot(3, Binding.None, 1, 1, 1, 1)] Vector1 Opacity,
+            [Slot(2, Binding.None)] out DynamicDimensionVector Out)
+        {
+            return
+                @"
+{
+    Out = lerp(Base, Blend, Opacity);
+}";
+        }
     }
 }

com.unity.shadergraph/Editor/Data/Nodes/Artistic/Normal/NormalStrengthNode.cs

             return
                 @"
 {
-    Out = {precision}3(In.rg * Strength, In.b);
+    Out = {precision}3(In.rg * Strength, lerp(1, In.b, saturate(Strength)));
 }
 ";
         }

com.unity.shadergraph/Editor/Data/Nodes/Procedural/Noise/SimpleNoiseNode.cs

                 @"
 {
     float t = 0.0;
-    for(int i = 0; i < 3; i++)
-    {
-        float freq = pow(2.0, float(i));
-        float amp = pow(0.5, float(3-i));
-        t += unity_valueNoise(float2(UV.x*Scale/freq, UV.y*Scale/freq))*amp;
-    }
+
+    float freq = pow(2.0, float(0));
+    float amp = pow(0.5, float(3-0));
+    t += unity_valueNoise(float2(UV.x*Scale/freq, UV.y*Scale/freq))*amp;
+
+    freq = pow(2.0, float(1));
+    amp = pow(0.5, float(3-1));
+    t += unity_valueNoise(float2(UV.x*Scale/freq, UV.y*Scale/freq))*amp;
+
+    freq = pow(2.0, float(2));
+    amp = pow(0.5, float(3-2));
+    t += unity_valueNoise(float2(UV.x*Scale/freq, UV.y*Scale/freq))*amp;
+
     Out = t;
 }
 ";

com.unity.shadergraph/Editor/Data/Nodes/Procedural/Shape/PolygonNode.cs

             return
                 @"
 {
-    {precision} tau = 6.28318530718;
-    {precision}2 uv = (UV * 2 - 1) / {precision}2(Width, Height);
+    {precision} pi = 3.14159265359;
+    {precision} aWidth = Width * cos(pi / Sides);
+    {precision} aHeight = Height * cos(pi / Sides);
+    {precision}2 uv = (UV * 2 - 1) / {precision}2(aWidth, aHeight);
-    {precision} r = tau / Sides;
+    {precision} r = 2 * pi / Sides;
     {precision} distance = cos(floor(0.5 + pCoord / r) * r - pCoord) * length(uv);
     Out = saturate((1 - distance) / fwidth(distance));
 }