function ortho(left, right, bottom, top, near, far, dst) {
  dst = dst || new MatType(16);
  dst[0] = 2 / (right - left);
  dst[1] = 0;
  dst[2] = 0;
  dst[3] = 0;
  dst[4] = 0;
  dst[5] = 2 / (top - bottom);
  dst[6] = 0;
  dst[7] = 0;
  dst[8] = 0;
  dst[9] = 0;
  dst[10] = 2 / (near - far);
  dst[11] = 0;
  dst[12] = (right + left) / (left - right);
  dst[13] = (top + bottom) / (bottom - top);
  dst[14] = (far + near) / (near - far);
  dst[15] = 1;
  return dst;
}
Computes a 4-by-4 orthogonal transformation matrix given the left, right,
bottom, and top dimensions of the near clipping plane as well as the
near and far clipping plane distances.
@param {number} left Left side of the near clipping plane viewport.
@param {number} right Right side of the near clipping plane viewport.
@param {number} bottom Bottom of the near clipping plane viewport.
@param {number} top Top of the near clipping plane viewport.
@param {number} near The depth (negative z coordinate)
    of the near clipping plane.
@param {number} far The depth (negative z coordinate)
    of the far clipping plane.
@param {module:twgl/m4.Mat4} [dst] Output matrix. If not passed a new one is created.
@return {module:twgl/m4.Mat4} The perspective matrix.
@memberOf module:twgl/m4