Function prefilter_environment_cubemap_fragment

pub fn prefilter_environment_cubemap_fragment(
    environment_cubemap: &Cubemap,
    sampler: &Sampler,
    in_pos: Vec3,
    in_roughness: f32,
    frag_color: &mut Vec4,
)

Fragment shader for rendering a “prefilter environment” cubemap.

Lambertian prefilter.