/* *  Simple trackball-like motion adapted (ripped off) from projtex.c *  (written by David Yu and David Blythe).  See the SIGGRAPH '96 *  Advanced OpenGL course notes. *//* includes */#include <math.h>#include <assert.h>#include <GL/glut.h>#include "tb.h"#include "trackball.h"/* globals */static GLuint    tb_lasttime;float curquat[4];float lastquat[4];int beginx, beginy;static GLuint    tb_width;static GLuint    tb_height;static GLint     tb_button = -1;static GLboolean tb_tracking = GL_FALSE;static GLboolean tb_animate = GL_TRUE;static void_tbAnimate(void){  add_quats(lastquat, curquat, curquat);  glutPostRedisplay();}void_tbStartMotion(int x, int y, int time){  assert(tb_button != -1);  glutIdleFunc(0);  tb_tracking = GL_TRUE;  tb_lasttime = time;  beginx = x;  beginy = y;}void_tbStopMotion(unsigned time){  assert(tb_button != -1);  tb_tracking = GL_FALSE;  if (time == tb_lasttime && tb_animate) {    glutIdleFunc(_tbAnimate);  } else {    if (tb_animate) {      glutIdleFunc(0);    }  }}voidtbAnimate(GLboolean animate){  tb_animate = animate;}voidtbInit(GLuint button){  tb_button = button;  trackball(curquat, 0.0, 0.0, 0.0, 0.0);}voidtbMatrix(void){  GLfloat m[4][4];  assert(tb_button != -1);  build_rotmatrix(m, curquat);  glMultMatrixf(&m[0][0]);}voidtbReshape(int width, int height){  assert(tb_button != -1);  tb_width  = width;  tb_height = height;}voidtbMouse(int button, int state, int x, int y){  assert(tb_button != -1);  if (state == GLUT_DOWN && button == tb_button)    _tbStartMotion(x, y, glutGet(GLUT_ELAPSED_TIME));  else if (state == GLUT_UP && button == tb_button)    _tbStopMotion(glutGet(GLUT_ELAPSED_TIME));}voidtbMotion(int x, int y){  if (tb_tracking) {    trackball(lastquat,      (2.0 * beginx - tb_width) / tb_width,      (tb_height - 2.0 * beginy) / tb_height,      (2.0 * x - tb_width) / tb_width,      (tb_height - 2.0 * y) / tb_height      );    beginx = x;    beginy = y;    tb_animate = 1;    tb_lasttime = glutGet(GLUT_ELAPSED_TIME);    _tbAnimate();  }}