Minor changes

Signed-off-by: Robear Selwans <robear.selwans@outlook.com>

assets/shaders/_builtins/PBR.glsl

@@ -0,0 +1,40 @@
+#ifndef EV_GLSL_PBR_H
+#define EV_GLSL_PBR_H
+
+float DistributionGGX(vec3 N, vec3 H, float a)
+{
+  float a2 = a*a;
+  float NdotH = max(dot(N,H),0.0);
+  float NdotH2 = NdotH*NdotH;
+
+  float num = a2;
+  float denom = (NdotH2 * (a2 - 1.0) + 1.0);
+  denom = PI * denom * denom;
+
+  return num/denom;
+}
+
+float GeometrySchlickGGX(float NdotV, float k)
+{
+    float nom   = NdotV;
+    float denom = NdotV * (1.0 - k) + k;
+
+    return nom / denom;
+}
+  
+float GeometrySmith(vec3 N, vec3 V, vec3 L, float k)
+{
+    float NdotV = max(dot(N, V), 0.0);
+    float NdotL = max(dot(N, L), 0.0);
+    float ggx1 = GeometrySchlickGGX(NdotV, k);
+    float ggx2 = GeometrySchlickGGX(NdotL, k);
+
+    return ggx1 * ggx2;
+}
+
+vec3 fresnelSchlick(float cosTheta, vec3 F0)
+{
+    return F0 + (1.0 - F0) * pow(1.0 - cosTheta, 5.0);
+}
+
+#endif

assets/shaders/_builtins/macros.glsl

@@ -0,0 +1,7 @@
+#ifndef EV_GLSL_MACROS_H
+#define EV_GLSL_MACROS_H
+
+#define __EV_CAT_IMPL(a,...) a##__VA_ARGS__
+#define EV_CAT(a,...) __EV_CAT_IMPL(a, __VA_ARGS__)
+
+#endif