modeling/src/maths/mat4/rotateY.js

  1. const { sin, cos } = require('../utils/trigonometry')
  3. /**
  4.  * Rotates a matrix by the given angle around the Y axis.
  5.  *
  6.  * @param {mat4} out - receiving matrix
  7.  * @param {mat4} matrix - matrix to rotate
  8.  * @param {Number} radians - angle to rotate the matrix by
  9.  * @returns {mat4} out
  10.  * @alias module:modeling/maths/mat4.rotateY
  11.  */
  12. const rotateY = (out, matrix, radians) => {
  13.   const s = sin(radians)
  14.   const c = cos(radians)
  15.   const a00 = matrix[0]
  16.   const a01 = matrix[1]
  17.   const a02 = matrix[2]
  18.   const a03 = matrix[3]
  19.   const a20 = matrix[8]
  20.   const a21 = matrix[9]
  21.   const a22 = matrix[10]
  22.   const a23 = matrix[11]
  24.   if (matrix !== out) { // If the source and destination differ, copy the unchanged rows
  25.     out[4] = matrix[4]
  26.     out[5] = matrix[5]
  27.     out[6] = matrix[6]
  28.     out[7] = matrix[7]
  29.     out[12] = matrix[12]
  30.     out[13] = matrix[13]
  31.     out[14] = matrix[14]
  32.     out[15] = matrix[15]
  33.   }
  35.   // Perform axis-specific matrix multiplication
  36.   out[0] = a00 * c - a20 * s
  37.   out[1] = a01 * c - a21 * s
  38.   out[2] = a02 * c - a22 * s
  39.   out[3] = a03 * c - a23 * s
  40.   out[8] = a00 * s + a20 * c
  41.   out[9] = a01 * s + a21 * c
  42.   out[10] = a02 * s + a22 * c
  43.   out[11] = a03 * s + a23 * c
  44.   return out
  45. }
  47. module.exports = rotateY