Re: [Closed REQ 5690]: rotation formula

[daemon]

The rotations are expressed, not as Euler angles, but as vectors whose
direction gives the axis of rotation and whose magnitude gives the
rotation angle (in radians).  The rotation matrix for "rotate X Y Z" comes from

  a = magnitude of vector(X Y Z)
  (x y z) = (X Y Z) / a;		(so (x y z) forms a unit vector)

  s = sin(a)
  c = cos(a)
  v = 1-c

Now the rotation matrix is

  x^2*v + c		x*y*v + z*s		x*z*v - y*s		0

  x*y*v - z*s		y^2*v + c		y*z*v + x*s		0

  x*z*v + y*s		y*z*v - x*s		z^2*v + c		0

  0			0			0			1

If you get the geomview source code, this appears in
   src/bin/geomview/common/transform.c  	(see _rotate()) and
   src/lib/geometry/transform3/tm3rotate.c	(see Tm3Rotate())