vec_rotate2()

vec_rotate2	(	struct vector *	x1,
		struct vector *	nu,
		struct vector *	x0,
		DOUBLE	theta
	)

Rotates a point of coordinates x1 of the angle theta around the axis defined by the vector nu (not need to be unitary), applied at point x0. The original vector is overwritten.

Parameters

[in,out]	x1
[in]	x0
[in]	nu
[in]	theta

                                                                                       {

  DOUBLE x,y,z;
  DOUBLE a,b,c;
  DOUBLE u,v,w;
  struct vector vtmp;

  x = x1->x;
  y = x1->y;
  z = x1->z;

  a = x0->x;
  b = x0->y;
  c = x0->z;

  u = (nu->x)/vec_mod(*nu);
  v = (nu->y)/vec_mod(*nu);
  w = (nu->z)/vec_mod(*nu);

  vtmp.x = (a*(v*v + w*w) - u*(b*v + c*w - u*x - v*y - w*z))*(1.0 - cos(theta)) + x*cos(theta) + (-c*v + b*w - w*y + v*z)*sin(theta);
  vtmp.y = (b*(u*u + w*w) - v*(a*u + c*w - u*x - v*y - w*z))*(1.0 - cos(theta)) + y*cos(theta) + (+c*u - a*w + w*x - u*z)*sin(theta);
  vtmp.z = (c*(u*u + v*v) - w*(a*u + b*v - u*x - v*y - w*z))*(1.0 - cos(theta)) + z*cos(theta) + (-b*u + a*v - v*x + u*y)*sin(theta);

  x1->x = vtmp.x;
  x1->y = vtmp.y;
  x1->z = vtmp.z;
}