TRACKBAL.H

/* 
 * trackball.h 
 * A virtual trackball implementation 
 * Written by Gavin Bell for Silicon Graphics, November 1988. 
 */ 
 
/* 
 * Initialize trackball in win32 environment 
 */ 
extern void 
trackball_Init( GLint width, GLint height ); 
 
extern void 
trackball_Resize( GLint width, GLint height ); 
 
extern GLenum  
trackball_MouseDown( AUX_EVENTREC *event ); 
 
extern GLenum  
trackball_MouseUp( AUX_EVENTREC *event ); 
 
/* These next Mouse fns are required if both the trackbal and user 
 * need mouse events.  Otherwise, can just supply above two functions 
 * to tk to call 
 */ 
 
/* 
 * Mouse functions called directly on events 
 */ 
extern void 
trackball_MouseDownEvent( int mouseX, int mouseY, GLenum button ); 
 
extern void 
trackball_MouseUpEvent( int mouseX, int mouseY, GLenum button ); 
 
/* 
 * Functions to register mouse event callbacks 
 */ 
extern void  
trackball_MouseDownFunc(GLenum (*)(int, int, GLenum)); 
 
extern void  
trackball_MouseUpFunc(GLenum (*)(int, int, GLenum)); 
 
/* 
 * Calculate rotation matrix based on mouse movement 
 */ 
void 
trackball_CalcRotMatrix( GLfloat matRot[4][4] ); 
 
/* 
 * Pass the x and y coordinates of the last and current positions of 
 * the mouse, scaled so they are from (-1.0 ... 1.0). 
 * 
 * if ox,oy is the window's center and sizex,sizey is its size, then 
 * the proper transformation from screen coordinates (sc) to world 
 * coordinates (wc) is: 
 * wcx = (2.0 * (scx-ox)) / (float)sizex - 1.0 
 * wcy = (2.0 * (scy-oy)) / (float)sizey - 1.0 
 * 
 * The resulting rotation is returned as a quaternion rotation in the 
 * first paramater. 
 */ 
void 
trackball_calc_quat(float q[4], float p1x, float p1y, float p2x, float p2y); 
 
/* 
 * Given two quaternions, add them together to get a third quaternion. 
 * Adding quaternions to get a compound rotation is analagous to adding 
 * translations to get a compound translation.  When incrementally 
 * adding rotations, the first argument here should be the new 
 * rotation, the second and third the total rotation (which will be 
 * over-written with the resulting new total rotation). 
 */ 
void 
trackball_add_quats(float *q1, float *q2, float *dest); 
 
/* 
 * A useful function, builds a rotation matrix in Matrix based on 
 * given quaternion. 
 */ 
void 
trackball_build_rotmatrix(float m[4][4], float q[4]); 
 
/* 
 * This function computes a quaternion based on an axis (defined by 
 * the given vector) and an angle about which to rotate.  The angle is 
 * expressed in radians.  The result is put into the third argument. 
 */ 
void 
trackball_axis_to_quat(float a[3], float phi, float q[4]);