modeling/src/maths/mat4/rotateY.js

/**
 * Rotates a matrix by the given angle around the Y axis.
 *
 * @param {mat4} out - receiving matrix
 * @param {mat4} matrix - matrix to rotate
 * @param {Number} radians - angle to rotate the matrix by
 * @returns {mat4} out
 * @alias module:modeling/maths/mat4.rotateY
 */
const rotateY = (out, matrix, radians) => {
  const s = Math.sin(radians)
  const c = Math.cos(radians)
  const a00 = matrix[0]
  const a01 = matrix[1]
  const a02 = matrix[2]
  const a03 = matrix[3]
  const a20 = matrix[8]
  const a21 = matrix[9]
  const a22 = matrix[10]
  const a23 = matrix[11]

  if (matrix !== out) { // If the source and destination differ, copy the unchanged rows
    out[4] = matrix[4]
    out[5] = matrix[5]
    out[6] = matrix[6]
    out[7] = matrix[7]
    out[12] = matrix[12]
    out[13] = matrix[13]
    out[14] = matrix[14]
    out[15] = matrix[15]
  }

  // Perform axis-specific matrix multiplication
  out[0] = a00 * c - a20 * s
  out[1] = a01 * c - a21 * s
  out[2] = a02 * c - a22 * s
  out[3] = a03 * c - a23 * s
  out[8] = a00 * s + a20 * c
  out[9] = a01 * s + a21 * c
  out[10] = a02 * s + a22 * c
  out[11] = a03 * s + a23 * c
  return out
}

module.exports = rotateY