Physical based rendering has become a common lighting model for decent engines like Unreal Engine 4, Unity, etc. I’ve found several implementations on the web. And made a simple application based on Shtille Engine framework which allows to test its visual appearance. The PBR material should be UE4-like (consist of 4 textures: albedo map, normal map, roughness map and metallic map). There’s a cool site with free PBR textures: https://freepbr.com/ I’ve decided to test some metal material, this is how it looks like:

So I’ve got the reference image, and now I’m able to start testing different approaches. Here’s the results:

The third result is taken from Khronos PBR demo, it shows the best result. Then I started to test mipmapped cubemap. It is used for realistic model.

vec3 diffuseLight = SrgbToLinear(texture(u_diffuse_env_sampler, n)).rgb;
vec3 specularLight = SrgbToLinear(textureLod(u_specular_env_sampler, reflection, lod)).rgb;

But the lower mipmap level is, the bigger becomes artefacts on the edges. This way I concluded two things:

• Diffuse environment map is irradiance map
• Specular environment map is prefiltered map

I found the way to generate both of these maps, based on some cubemap texture. Here’s the result with proper maps:

As you may see, it’s rather similar to the reference image. This is the result I’ve decided to end with.