Function _glslRadTanFisheye

src/shaders/undistortion.ts:857–884

(p: Vec2, i: CameraIntrinsics)

// Mirrors distortRadTanFisheye().
function _glslRadTanFisheye(p: Vec2, i: CameraIntrinsics): Vec2 {
  const r = Math.hypot(p.x, p.y);
  if (r < 0.00001) return { x: p.x, y: p.y };
  const theta = Math.atan(r);
  const uux   = p.x * (theta / r);
  const uuy   = p.y * (theta / r);
  const theta2  = uux * uux + uuy * uuy; // = theta²
  const theta4  = theta2 * theta2;
  const theta6  = theta4 * theta2;
  const theta8  = theta4 * theta4;
  const theta10 = theta8 * theta2;
  const theta12 = theta10 * theta2;
  const thRadial = 1.0 + i.k1 * theta2 + i.k2 * theta4 + i.k3 * theta6
                       + i.k4 * theta8 + i.k5 * theta10 + i.k6 * theta12;
  const x  = thRadial * uux;
  const y  = thRadial * uuy;
  const x2 = x * x, y2 = y * y;
  const xy = x * y;
  const r2 = x2 + y2;
  const r4 = r2 * r2;
  // COLMAP convention: i.p1=COLMAP p0, i.p2=COLMAP p1
  const dxTang = i.p1 * (r2 + 2.0 * x2) + 2.0 * i.p2 * xy;
  const dyTang = 2.0 * i.p1 * xy + i.p2 * (r2 + 2.0 * y2);
  const dxTp = i.sx1 * r2 + i.sy1 * r4;
  const dyTp = i.sx2 * r2 + i.sy2 * r4;
  // p + delta, where delta = vec2(x + dxTang + dxTp − p.x, y + dyTang + dyTp − p.y)
  return { x: x + dxTang + dxTp, y: y + dyTang + dyTp };
}

// Mirrors distortDivision().
function _glslDivision(p: Vec2, i: CameraIntrinsics): Vec2 {