Add iridescence to parallax shader

Add texture slots for iridescence using a shaderamp and a normal map,
and an offset parameter to control whether iridescence is most visible
from the side (0.0) or head on (0.5).

Include two sample textures to use with the effect.

2 files changed, 80 insertions, 12 deletions

diff --git a/Shaders/parallax/parallax.shader b/Shaders/parallax/parallax.shader
index 4f71fb8..a63c90b 100644
--- a/Shaders/parallax/parallax.shader
+++ b/Shaders/parallax/parallax.shader
@@ -1,4 +1,4 @@
-Shader "yum_food/parallax"
+Shader "yum_food/parallax"
 {
   Properties
   {
@@ -34,6 +34,10 @@
     _Layer2_XScale("Layer 2 X Scale", float) = 1.0
     _Layer2_YScale("Layer 2 Y Scale", float) = 1.0
     _Layer2_Emission("Layer 2 Emission strength", float) = 0.0
+
+    _Iridescence_Ramp("Iridescence ramp", 2D) = "black" {}
+    _Iridescence_Normal("Iridescence normal", 2D) = "bump" {}
+    _Iridescence_Offset("Iridescence offset", float) = 0.0
   }
   SubShader
   {
@@ -58,6 +62,11 @@
 
       #define FORWARD_BASE_PASS
 
+      #define LAYER0_TEXTURES_ON
+      #define LAYER1_TEXTURES_ON
+      #define LAYER2_TEXTURES_ON
+      #define IRIDESCENCE_TEXTURES_ON
+
       #include "parallax_lighting.cginc"
       ENDCG
     }
@@ -80,6 +89,11 @@
       #pragma vertex vert
       #pragma fragment frag
 
+      #define LAYER0_TEXTURES_ON
+      #define LAYER1_TEXTURES_ON
+      #define LAYER2_TEXTURES_ON
+      #define IRIDESCENCE_TEXTURES_ON
+
       #include "parallax_lighting.cginc"
       ENDCG
     }
diff --git a/Shaders/parallax/parallax_lighting.cginc b/Shaders/parallax/parallax_lighting.cginc
index a3a7eb1..eba6af9 100644
--- a/Shaders/parallax/parallax_lighting.cginc
+++ b/Shaders/parallax/parallax_lighting.cginc
@@ -20,21 +20,26 @@ float _Min_Hit_Dist;
 float _Max_Dist;
 float _Ray_March_Steps;
 
+#ifdef LAYER0_TEXTURES_ON
 sampler2D _Layer0_BaseColor;
-sampler2D _Layer1_BaseColor;
-sampler2D _Layer2_BaseColor;
-
 sampler2D _Layer0_Normal;
-sampler2D _Layer1_Normal;
-sampler2D _Layer2_Normal;
-
 sampler2D _Layer0_Metallic;
-sampler2D _Layer1_Metallic;
-sampler2D _Layer2_Metallic;
-
 sampler2D _Layer0_Roughness;
+#endif
+
+#ifdef LAYER1_TEXTURES_ON
+sampler2D _Layer1_BaseColor;
+sampler2D _Layer1_Normal;
+sampler2D _Layer1_Metallic;
 sampler2D _Layer1_Roughness;
+#endif
+
+#ifdef LAYER2_TEXTURES_ON
+sampler2D _Layer2_BaseColor;
+sampler2D _Layer2_Normal;
+sampler2D _Layer2_Metallic;
 sampler2D _Layer2_Roughness;
+#endif
 
 float _Layer0_Offset;
 float _Layer0_XScale;
@@ -51,6 +56,12 @@ float _Layer2_XScale;
 float _Layer2_YScale;
 float _Layer2_Emission;
 
+#ifdef IRIDESCENCE_TEXTURES_ON
+sampler2D _Iridescence_Ramp;
+sampler2D _Iridescence_Normal;
+float _Iridescence_Offset;
+#endif
+
 void getVertexLightColor(inout v2f i)
 {
   #if defined(VERTEXLIGHT_ON)
@@ -98,12 +109,18 @@ float4 getLayerBaseColor(in float2 uv, in int layer)
 {
   [forcecase]
   switch (layer) {
+    #ifdef LAYER0_TEXTURES_ON
     case 0:
       return tex2Dgrad(_Layer0_BaseColor, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER1_TEXTURES_ON
     case 1:
       return tex2Dgrad(_Layer1_BaseColor, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER2_TEXTURES_ON
     case 2:
       return tex2Dgrad(_Layer2_BaseColor, uv, ddx(uv.x), ddy(uv.y));
+    #endif
     default:
       return 0.0;
   }
@@ -113,12 +130,18 @@ float3 getLayerNormal(in float2 uv, in int layer)
 {
   [forcecase]
   switch (layer) {
+    #ifdef LAYER0_TEXTURES_ON
     case 0:
       return tex2Dgrad(_Layer0_Normal, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER1_TEXTURES_ON
     case 1:
       return tex2Dgrad(_Layer1_Normal, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER2_TEXTURES_ON
     case 2:
       return tex2Dgrad(_Layer2_Normal, uv, ddx(uv.x), ddy(uv.y));
+    #endif
     default:
       return 0.0;
   }
@@ -128,12 +151,18 @@ float getLayerMetallic(in float2 uv, in int layer)
 {
   [forcecase]
   switch (layer) {
+    #ifdef LAYER0_TEXTURES_ON
     case 0:
       return tex2Dgrad(_Layer0_Metallic, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER1_TEXTURES_ON
     case 1:
       return tex2Dgrad(_Layer1_Metallic, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER2_TEXTURES_ON
     case 2:
       return tex2Dgrad(_Layer2_Metallic, uv, ddx(uv.x), ddy(uv.y));
+    #endif
     default:
       return 0.0;
   }
@@ -143,12 +172,18 @@ float getLayerRoughness(in float2 uv, in int layer)
 {
   [forcecase]
   switch (layer) {
+    #ifdef LAYER0_TEXTURES_ON
     case 0:
       return tex2Dgrad(_Layer0_Roughness, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER1_TEXTURES_ON
     case 1:
       return tex2Dgrad(_Layer1_Roughness, uv, ddx(uv.x), ddy(uv.y));
+    #endif
+    #ifdef LAYER2_TEXTURES_ON
     case 2:
       return tex2Dgrad(_Layer2_Roughness, uv, ddx(uv.x), ddy(uv.y));
+    #endif
     default:
       return 0.0;
   }
@@ -298,15 +333,34 @@ float4 effect(inout v2f i, out float depth)
       if (color.a < 0.9) {
         color.a = 0.0;
       }
-      const float3 normal = getLayerNormal(uv, (int) layer);
+      float3 normal = getLayerNormal(uv, (int) layer);
       const float metallic = getLayerMetallic(uv, (int) layer);
       const float smoothness = 1.0 - getLayerRoughness(uv, (int) layer);
 
       bool custom_cubemap = true;
-      float4 lit_color;
+
+      // Iridescence
+#ifdef IRIDESCENCE_TEXTURES_ON
+      if (smoothness > 0.0)
+      {
+        float3 ir_normal = normalize(tex2Dgrad(_Iridescence_Normal, uv, ddx(uv.x), ddy(uv.y)));
+
+        float3 camera_position = _WorldSpaceCameraPos.xyz;
+
+        float3 obj_normal = i.normal;
+
+        float ndotl = dot(view_dir, normalize(normal + obj_normal));
+        ndotl = glsl_mod(ndotl + _Iridescence_Offset, 1.0);
+
+        float3 ir_color = tex2Dgrad(_Iridescence_Ramp, ndotl, ddx(ndotl), ddy(ndotl));
+        color.rgb = lerp(color.rgb, ir_color, dot(ir_color, ir_color));
+        normal = lerp(normal, ir_normal, dot(ir_color, ir_color));
+      }
+#endif
 
       // Hack: Bright cubemaps cause glare on rough surfaces. To prevent this,
       // switch to unlit shading when shading a perfectly rough material.
+      float4 lit_color;
       if (smoothness == 0.0) {
         lit_color = color;
       } else {