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SO3.xs  view on Meta::CPAN

#   Note that this trick does not work with an angle of 180 degrees;
#   here, we take an arbitrary vector and its rotated image and compute the
#   normalized sum. Take a different vector if norm is zero. There are 
#   cases when we must do this three times.
#
#   XXX have to put a bit more thought into this. Does it really work that way,
#   or did I still miss a point?

void
turning_angle_and_dir(...)
	PPCODE:
	{
          double angle, *dir, v2[3], v3[3], norm;
          char *cdir;

	  if(   (items!=1 && items != 2)
             || SvTYPE(SvRV(ST(0)))!=SVt_PVMG
             || 0==(cdir=alloca(1+3*sizeof(double))))
          {
             croak(croak_turning_angle_and_dir);
          }

SO3.xs  view on Meta::CPAN

# (1) Determine q (theta) from [2][2] element.
# (2) Determine r (psi)   from [0][2] and [1][2] elements. If theta=0, we can also set psi=0. 
#     (Since all that remains is a z-rotation or z-rotation with 180deg x-rotation, 
#     both characterized by a single angle)
# (3) Do some math to determine phi from [1][0] and [1][1] elements if theta=0, 
#     otherwise use [2][0] and [2][1] elements.


void
euler_angles_zxz(...)
	PPCODE:
         {
	  if(   (items!=1 && items!=2)
             || SvTYPE(SvRV(ST(0)))!=SVt_PVMG)
          {
             croak(croak_euler_angles_zxz);
          }
          else
          {
            int i;
            double phi, theta, psi, cos_theta, sin_theta, cos_psi, sin_psi, sin_phi, cos_phi;

SO3.xs  view on Meta::CPAN

#     [0][0]: cos r cos -h - sin r sin -h     => cos (r-h)
#     [0][2]: sin r cos -h + cos r sin -h     => sin (r-h)
#
# Heading does not make sense for an airplane going straight up or straight down.
# Therefore, we take this last angle to be all roll.
#
# => heading=0, roll=atan2(sin_roll, cos_roll)

void 
euler_angles_yxz(...)
	PPCODE:
	{
          int i;
          double heading, pitch, roll, cos_heading, cos_pitch, cos_roll, sin_heading, sin_pitch, sin_roll;
          Math__SO3 so3;

	  if(   (items!=1 && items!=2)
             || SvTYPE(SvRV(ST(0)))!=SVt_PVMG)
          {
             croak(croak_euler_angles_zxz);
          }