Added PBR image based lighting example

data/shaders/pbribl/skybox.frag

@@ -0,0 +1,38 @@
+#version 450
+
+layout (binding = 2) uniform samplerCube samplerEnv;
+
+layout (location = 0) in vec3 inUVW;
+
+layout (location = 0) out vec4 outColor;
+
+layout (binding = 1) uniform UBOShared {
+	float exposure;
+	float gamma;
+} uboShared;
+
+// From http://filmicworlds.com/blog/filmic-tonemapping-operators/
+vec3 Uncharted2Tonemap(vec3 color)
+{
+	float A = 0.15;
+	float B = 0.50;
+	float C = 0.10;
+	float D = 0.20;
+	float E = 0.02;
+	float F = 0.30;
+	float W = 11.2;
+	return ((color*(A*color+C*B)+D*E)/(color*(A*color+B)+D*F))-E/F;
+}
+
+void main() 
+{
+	vec3 color = pow(texture(samplerEnv, inUVW).rgb, vec3(2.2));
+
+	color = Uncharted2Tonemap(color * uboShared.exposure);
+	color = color * (1.0 / Uncharted2Tonemap(vec3(11.2)));
+	
+	// gamma correction
+	color = pow(color, vec3(1.0 / uboShared.gamma));
+	
+	outColor = vec4(color, 1.0);
+}