// 3D SDF primitives
fn sdSphere(p: vec3<f32>, r: f32) -> f32 {
    return length(p) - r;
}

fn sdBox(p: vec3<f32>, b: vec3<f32>) -> f32 {
    let q = abs(p) - b;
    return length(max(q, vec3<f32>(0.0))) + min(max(q.x, max(q.y, q.z)), 0.0);
}

fn sdTorus(p: vec3<f32>, t: vec2<f32>) -> f32 {
    let q = vec2<f32>(length(p.xz) - t.x, p.y);
    return length(q) - t.y;
}

fn sdPlane(p: vec3<f32>, n: vec3<f32>, h: f32) -> f32 {
    return dot(p, n) + h;
}

// 2D SDF primitives
fn sdBox2D(p: vec2<f32>, b: vec2<f32>) -> f32 {
    let d = abs(p) - b;
    return length(max(d, vec2<f32>(0.0))) + min(max(d.x, d.y), 0.0);
}

// Approximate
fn sdEllipse(p: vec2<f32>, ab: vec2<f32>) -> f32 {
    let d = length(p / ab);
    return length(p) * (1.0 - 1.0 / d);
}