trackball.h File Reference

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Functions
void	trackball (double q[4], double p1x, double p1y, double p2x, double p2y)
void	add_quats (double *q1, double *q2, double *dest)
void	build_rotmatrix (float m[4][4], double q[4])
void	axis_to_quat (double a[3], double phi, double q[4])

Function Documentation

add_quats()

void add_quats	(	double *	q1,
		double *	q2,
		double *	dest
	)

axis_to_quat()

void axis_to_quat	(	double	a[3],
		double	phi,
		double	q[4]
	)

Definition at line 205 of file trackball.cpp.

{
 vnormal( a );
 vcopy( a, q );
 vscale( q, (double) sin( phi / 2.0) );
 q[3] = (double) cos( phi / 2.0 );
}

References vcopy(), vnormal(), and vscale().

Referenced by trackball().

build_rotmatrix()

void build_rotmatrix	(	float	m[4][4],
		double	q[4]
	)

Definition at line 306 of file trackball.cpp.

{
 m[0][0] = (float)(1.0 - 2.0 * (q[1] * q[1] + q[2] * q[2]));
 m[0][1] = (float)(2.0 * (q[0] * q[1] - q[2] * q[3]));
 m[0][2] = (float)(2.0 * (q[2] * q[0] + q[1] * q[3]));
 m[0][3] = 0.0f;
 
 m[1][0] = (float)(2.0 * (q[0] * q[1] + q[2] * q[3]));
 m[1][1] = (float)(1.0 - 2.0f * (q[2] * q[2] + q[0] * q[0]));
 m[1][2] = (float)(2.0 * (q[1] * q[2] - q[0] * q[3]));
 m[1][3] = 0.0f;
 
 m[2][0] = (float)(2.0 * (q[2] * q[0] - q[1] * q[3]));
 m[2][1] = (float)(2.0 * (q[1] * q[2] + q[0] * q[3]));
 m[2][2] = (float)(1.0 - 2.0 * (q[1] * q[1] + q[0] * q[0]));
 m[2][3] = 0.0f;
 
 m[3][0] = 0.0f;
 m[3][1] = 0.0f;
 m[3][2] = 0.0f;
 m[3][3] = 1.0f;
}

Referenced by TRACK_BALL::Drag(), and TRACK_BALL::Interpolate().

trackball()

void trackball	(	double	q[4],
		double	p1x,
		double	p1y,
		double	p2x,
		double	p2y
	)

Definition at line 155 of file trackball.cpp.

{
 double a[3]; /* Axis of rotation */
 double phi; /* how much to rotate about axis */
 double p1[3], p2[3], d[3];
 double t;
 
 if( p1x == p2x && p1y == p2y )
 {
 /* Zero rotation */
 vzero( q );
 q[3] = 1.0;
 return;
 }
 
 /*
 * First, figure out z-coordinates for projection of P1 and P2 to
 * deformed sphere
 */
 vset( p1, p1x, p1y, tb_project_to_sphere( TRACKBALLSIZE, p1x, p1y ) );
 vset( p2, p2x, p2y, tb_project_to_sphere( TRACKBALLSIZE, p2x, p2y ) );
 
 /*
 * Now, we want the cross product of P1 and P2
 */
 vcross(p2,p1,a);
 
 /*
 * Figure out how much to rotate around that axis.
 */
 vsub( p1, p2, d );
 t = vlength( d ) / (2.0f * TRACKBALLSIZE);
 
 /*
 * Avoid problems with out-of-control values...
 */
 if( t > 1.0 )
 t = 1.0;
 
 if( t < -1.0 )
 t = -1.0;
 
 phi = 2.0f * (double) asin( t );
 
 axis_to_quat( a, phi, q );
}

References axis_to_quat(), tb_project_to_sphere(), TRACKBALLSIZE, vcross(), vlength(), vset(), vsub(), and vzero().

Referenced by TRACK_BALL::Drag(), TRACK_BALL::Reset_T1(), and TRACK_BALL::TRACK_BALL().