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;
}