Merge pull request #76 from Unity-Technologies/Add-LatLong-reflection-support

HDRenderPipeline: Add support for LatLong reflection

Assets/ScriptableRenderLoop/HDRenderPipeline/Lighting/TilePass/TilePass.hlsl

 TEXTURECUBE_ARRAY(_CookieCubeTextures);
 SAMPLERCUBE(sampler_CookieCubeTextures);
 
-// Use texture array for reflection
+// Use texture array for reflection (or LatLong 2D array for mobile)
+#ifdef CUBE_ARRAY_NOT_SUPPORTED
+TEXTURE2D_ARRAY(_EnvTextures);
+SAMPLER2D(sampler_EnvTextures);
+#else
+#endif
 
 TEXTURECUBE(_SkyTexture);
 SAMPLERCUBE(sampler_SkyTexture); // NOTE: Sampler could be share here with _EnvTextures. Don't know if the shader compiler will complain...
     // This code will be inlined as lightLoopContext is hardcoded in the light loop
     if (lightLoopContext.sampleReflection == SINGLE_PASS_CONTEXT_SAMPLE_REFLECTION_PROBES)
     {
+        #ifdef CUBE_ARRAY_NOT_SUPPORTED
+        return SAMPLE_TEXTURE2D_ARRAY_LOD(_EnvTextures, sampler_EnvTextures, DirectionToLatLongCoordinate(texCoord), index, lod);
+        #else
+        #endif
     }
     else // SINGLE_PASS_SAMPLE_SKY
     {

Assets/ScriptableRenderLoop/ShaderLibrary/Common.hlsl

 }
 
 // ----------------------------------------------------------------------------
+// Texture format sampling
+// ----------------------------------------------------------------------------
+
+float2 DirectionToLatLongCoordinate(float3 dir)
+{
+    // coordinate frame is (-Z, X) meaning negative Z is primary axis and X is secondary axis.
+    return float2(1.0 - 0.5 * INV_PI * atan2(dir.x, -dir.z), asin(dir.y) * INV_PI + 0.5);
+}
+
+// ----------------------------------------------------------------------------
 // World position reconstruction / transformation
 // ----------------------------------------------------------------------------