BezierInfo-2/docs/chapters/pointvectors3d/projection.js

/**
 * A cabinet projection utility library
 */

// Universal projector function:

function project(point3d, offset = { x: 0, y: 0 }, phi = -Math.PI / 6) {
  // what they rarely tell you: if you want Z to "go up",
  // X to "come out of the screen", and Y to be the "left/right",
  // we need to switch some coordinates around:
  const a = point3d.y,
    b = -point3d.z,
    c = -point3d.x / 2;

  return {
    x: offset.x + a + c * Math.cos(phi),
    y: offset.y + b + c * Math.sin(phi),
  };
}

// and some planar projectors:

function projectXY(p, offset, phi) {
  return project({ x: p.x, y: p.y, z: 0 }, offset, phi);
}

function projectXZ(p, offset, phi) {
  return project({ x: p.x, y: 0, z: p.z }, offset, phi);
}

function projectYZ(p, offset, phi) {
  return project({ x: 0, y: p.y, z: p.z }, offset, phi);
}

export { project, projectXY, projectXZ, projectYZ };