R/rot_to_euler.R

In rayshader: Create Maps and Visualize Data in 2D and 3D

#'@title Rotation Matrix to Euler Angle Transform
#'
#'@description Transforms a rotation matrix (R_X R_Y R_Z) into Euler angles. 
#'
#'@param rotmat The rotation matrix. Can be 3x3 or 4x4 (homogeneous coordinates).
#'@return Euler angles in degrees. c(phi,theta,yaw)
#'@keywords internal
#'@examples
#'#None
rot_to_euler = function(rotmat) {
  if(abs(rotmat[3,2]) == 1) {
    if(rotmat[3,2] < 0) {
      x = -pi/2
    } else {
      x = pi/2
    }
    y = atan2(rotmat[1,1],rotmat[1,3])
    z = 0
  } else {
    x = atan2(-rotmat[2,3],rotmat[3,3])
    y = -asin(rotmat[1,3])
    sinz = cos(x) * rotmat[2,1] + sin(x) * rotmat[3,1]
    cosz = cos(x) * rotmat[2,2] + sin(x) * rotmat[3,2]
    z = atan2(sinz,cosz)
    if(x*180/pi < -90) {
      x = x + pi
    }
    if(x*180/pi > 90) {
      x = x - pi
    }
  }
  return(c(x, y, z)*180/pi)
}