From 361371b2a9909bc21a6f72af97cce4f7de0d8e5a Mon Sep 17 00:00:00 2001
From: Olivier Prat <olivier@zvork.fr>
Date: Fri, 5 Apr 2019 08:58:06 +0200
Subject: [PATCH] Added flag to enable / disable ambient fresnel LUT

---
 libraries/render-utils/src/LightAmbient.slh               | 8 ++++----
 libraries/render-utils/src/LightingModel.cpp              | 4 ++++
 libraries/render-utils/src/render-utils/ShaderConstants.h | 4 ++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/libraries/render-utils/src/LightAmbient.slh b/libraries/render-utils/src/LightAmbient.slh
index 8e7abd8861..cb76a8e545 100644
--- a/libraries/render-utils/src/LightAmbient.slh
+++ b/libraries/render-utils/src/LightAmbient.slh
@@ -30,13 +30,13 @@ vec4 evalSkyboxLight(vec3 direction, float lod) {
 LAYOUT(binding=RENDER_UTILS_TEXTURE_AMBIENT_FRESNEL) uniform sampler2D ambientFresnelLUT;
 
 vec3 fresnelSchlickAmbient(vec3 fresnelColor, float ndotd, float roughness) {
-#if 0
+#if RENDER_UTILS_ENABLE_AMBIENT_FRESNEL_LUT
+    vec2 ambientFresnel = texture(ambientFresnelLUT, vec2(roughness, ndotd)).xy;
+    return fresnelColor * ambientFresnel.x + vec3(ambientFresnel.y);
+#else
     float gloss = 1.0-roughness;
     float f = pow(1.0 - ndotd, 5.0);
     return fresnelColor + (max(vec3(gloss), fresnelColor) - fresnelColor) * f;
-#else
-    vec2 ambientFresnel = texture(ambientFresnelLUT, vec2(roughness, ndotd)).xy;
-    return fresnelColor * ambientFresnel.x + vec3(ambientFresnel.y);
 #endif
 }
 
diff --git a/libraries/render-utils/src/LightingModel.cpp b/libraries/render-utils/src/LightingModel.cpp
index cd49acd3da..5a9ab310c6 100644
--- a/libraries/render-utils/src/LightingModel.cpp
+++ b/libraries/render-utils/src/LightingModel.cpp
@@ -12,6 +12,8 @@
 #include "RandomAndNoise.h"
 #include "BRDF.h"
 
+#include "render-utils/ShaderConstants.h"
+
 #include <tbb/parallel_for.h>
 #include <tbb/blocked_range2d.h>
 
@@ -21,6 +23,7 @@ LightingModel::LightingModel() {
     Parameters parameters;
     _parametersBuffer = gpu::BufferView(std::make_shared<gpu::Buffer>(sizeof(Parameters), (const gpu::Byte*) &parameters, sizeof(Parameters)));
 
+#if RENDER_UTILS_ENABLE_AMBIENT_FRESNEL_LUT
     if (!_ambientFresnelLUT) {
         // Code taken from the IntegrateBRDF method as described in this talk :
         // https://cdn2.unrealengine.com/Resources/files/2013SiggraphPresentationsNotes-26915738.pdf
@@ -88,6 +91,7 @@ LightingModel::LightingModel() {
 
         _ambientFresnelLUT->assignStoredMip(0, N_roughness * N_NdotV * sizeof(LUTVector::value_type), (const gpu::Byte*)lut.data());
     }
+#endif
 }
 
 void LightingModel::setUnlit(bool enable) {
diff --git a/libraries/render-utils/src/render-utils/ShaderConstants.h b/libraries/render-utils/src/render-utils/ShaderConstants.h
index ffa580503b..76c8dd4981 100644
--- a/libraries/render-utils/src/render-utils/ShaderConstants.h
+++ b/libraries/render-utils/src/render-utils/ShaderConstants.h
@@ -14,6 +14,10 @@
 #ifndef RENDER_UTILS_SHADER_CONSTANTS_H
 #define RENDER_UTILS_SHADER_CONSTANTS_H
 
+// Feature enabling flags (possibly need to rebuild shaders if this changes)
+#define RENDER_UTILS_ENABLE_AMBIENT_FRESNEL_LUT 1
+
+// Binding slots
 #define RENDER_UTILS_ATTR_TEXCOORD01 0
 #define RENDER_UTILS_ATTR_COLOR 1