PBR materials

[kvark]

struct Texture;
type Color = [f32; 3];
type Vector = [f32; 3];
type Scalar = f32;
enum MaybeTexture<T> {
    Texture(Texture),
    Value(T),
}

struct Phong {
    diffuse: MaybeTexture<Color>,
    specular: MaybeTexture<Color>,
    normal: MaybeTexture<Vector>,
    glossiness: Scalar,
}

struct Metal {
    albedo: Color,
    reflection: Texture,
    glossiness: MaybeTexture<Scalar>,
    normal: Texture,
}

struct Dielectric {
    albedo: Texture,
    reflectivity: Scalar,
    transparency: Scalar,
    normal: Texture,
}

[kvark]

Relevant info: https://disney-animation.s3.amazonaws.com/library/s2012_pbs_disney_brdf_notes_v2.pdf http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf http://www.frostbite.com/2014/11/moving-frostbite-to-pbr/