Function applyRotation

src/index.js:271–289

* Apply rotation to a 3D point (same rotation as marker/arc shaders) * Uses rot * p (matrix times column vector) for world-to-view transformation * @param {[number, number, number]} p * @param {number} theta * @param {number} phi * @returns {[number, number, number]}

(p)

   * @returns {[number, number, number]}
   */
  function applyRotation(p) {
    const cx = Math.cos(theta)
    const cy = Math.cos(phi)
    const sx = Math.sin(theta)
    const sy = Math.sin(phi)

    const aspect = canvas.width / canvas.height

    // Rotated coordinates
    const rx = cy * p[0] + sy * p[2]
    const ry = sy * sx * p[0] + cx * p[1] - cy * sx * p[2]
    const rz = -sy * cx * p[0] + sx * p[1] + cy * cx * p[2]

    return [
      ((rx / aspect) * scaleOpt + offsetOpt[0] * scaleOpt * dpr / canvas.width + 1) / 2,
      (-ry * scaleOpt + offsetOpt[1] * scaleOpt * dpr / canvas.height + 1) / 2,
      rz >= 0 || rx * rx + ry * ry >= 0.64, // visible if in front OR outside globe silhouette
    ]
  }

  /**
   * Project a location to screen coordinates