New example, loading glTF scenes instead of individual OBJ. Showing simple path tracing and how to make it 3x faster.

ray_tracing_gltf/shaders/gltf.glsl

@@ -0,0 +1,60 @@
+
+struct GltfMaterial
+{
+  int shadingModel;  // 0: metallic-roughness, 1: specular-glossiness
+
+  // PbrMetallicRoughness
+  vec4  pbrBaseColorFactor;
+  int   pbrBaseColorTexture;
+  float pbrMetallicFactor;
+  float pbrRoughnessFactor;
+  int   pbrMetallicRoughnessTexture;
+
+  // KHR_materials_pbrSpecularGlossiness
+  vec4  khrDiffuseFactor;
+  int   khrDiffuseTexture;
+  vec3  khrSpecularFactor;
+  float khrGlossinessFactor;
+  int   khrSpecularGlossinessTexture;
+
+  int   emissiveTexture;
+  vec3  emissiveFactor;
+  int   alphaMode;
+  float alphaCutoff;
+  bool  doubleSided;
+
+  int   normalTexture;
+  float normalTextureScale;
+  int   occlusionTexture;
+  float occlusionTextureStrength;
+};
+
+struct PrimMeshInfo
+{
+  uint indexOffset;
+  uint vertexOffset;
+  int  materialIndex;
+};
+
+
+vec3 computeDiffuse(GltfMaterial mat, vec3 lightDir, vec3 normal)
+{
+  // Lambertian
+  float dotNL = max(dot(normal, lightDir), 0.0);
+  return mat.pbrBaseColorFactor.xyz * dotNL;
+}
+
+vec3 computeSpecular(GltfMaterial mat, vec3 viewDir, vec3 lightDir, vec3 normal)
+{
+  // Compute specular only if not in shadow
+  const float kPi        = 3.14159265;
+  const float kShininess = 60.0;
+
+  // Specular
+  const float kEnergyConservation = (2.0 + kShininess) / (2.0 * kPi);
+  vec3        V                   = normalize(-viewDir);
+  vec3        R                   = reflect(-lightDir, normal);
+  float       specular            = kEnergyConservation * pow(max(dot(V, R), 0.0), kShininess);
+
+  return vec3(specular);
+}