sdfIcosahedron

fn sdfIcosahedron(position: vec3<f32>, size: f32) -> f32 {
  var p = position;
  let s = size;
  
  // Constants for icosahedron
  let phi = 1.618033988749895;
  let a = s;
  let b = s * phi;
  
  // Compute distance to icosahedron
  p = abs(p / s);
  let d = p.x * p.y * p.z;
  let m = max(max(p.x, p.y), p.z);
  let n = min(min(p.x, p.y), p.z);
  let mid = p.x + p.y + p.z - m - n;
  
  // Calculate the signed distance
  let q = select(mid, d, m < phi * n);
  return (length(p) - phi) * s;
}