Function sample_cosine_hemisphere

tools/bloom-reference/src/main.rs:1185–1192

Cosine-weighted hemisphere sample, used for diffuse direction sampling. `rand` is two uniform samples in [0, 1)².

(rand: Vec2)

/// Cosine-weighted hemisphere sample, used for diffuse direction
/// sampling. `rand` is two uniform samples in [0, 1)².
fn sample_cosine_hemisphere(rand: Vec2) -> Vec3 {
    let r = rand.x.sqrt();
    let theta = 2.0 * std::f32::consts::PI * rand.y;
    let x = r * theta.cos();
    let y = r * theta.sin();
    let z = (1.0 - rand.x).max(0.0).sqrt();
    Vec3::new(x, y, z)
}

/// GGX VNDF sample — Heitz 2018 "Sampling the GGX Distribution of
/// Visible Normals". Gives better low-variance estimates than sampling