/* * 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 #include #include #include "trackball.h" #include using namespace std; /* globals */ static GLuint tb_lasttime; static GLfloat tb_lastposition[3]; static GLfloat tb_angle = 0.0; static GLfloat tb_axis[3]; static GLfloat tb_transform[4][4]; 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 GLfloat tb_inc_angle; /* functions */ static void _tbPointToVector(int x, int y, int width, int height, float v[3]) { float d, a; /* project x, y onto a hemi-sphere centered within width, height. */ v[0] = (2.0 * x - width) / width; v[1] = (height - 2.0 * y) / height; d = sqrt(v[0] * v[0] + v[1] * v[1]); v[2] = cos((3.14159265 / 2.0) * ((d < 1.0) ? d : 1.0)); a = 1.0 / sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]); v[0] *= a; v[1] *= a; v[2] *= a; } static void _tbAnimate(void) { glutPostRedisplay(); } void _tbStartMotion(int x, int y, int button, int time) { assert(tb_button != -1); glPushMatrix(); glLoadIdentity(); glRotatef(tb_angle, tb_axis[0], tb_axis[1], tb_axis[2]); glMultMatrixf((GLfloat *)tb_transform); glGetFloatv(GL_MODELVIEW_MATRIX, (GLfloat *)tb_transform); glPopMatrix(); tb_angle=0.0; tb_inc_angle=0.0; tb_tracking = GL_TRUE; tb_lasttime = time; _tbPointToVector(x, y, tb_width, tb_height, tb_lastposition); } void _tbStopMotion(int button, unsigned time) { assert(tb_button != -1); tb_tracking = GL_FALSE; glPushMatrix(); glLoadIdentity(); glRotatef(tb_angle, tb_axis[0], tb_axis[1], tb_axis[2]); glMultMatrixf((GLfloat *)tb_transform); glGetFloatv(GL_MODELVIEW_MATRIX, (GLfloat *)tb_transform); glPopMatrix(); tb_inc_angle=tb_angle/2.0/(double(time)-double(tb_lasttime)); tb_angle=0.0; } void tbAnimate(GLboolean animate) { tb_animate = animate; } void tbInit(GLuint button) { tb_button = button; tb_angle = 0.0; tb_inc_angle=0.0; /* put the identity in the trackball transform */ glPushMatrix(); glLoadIdentity(); glGetFloatv(GL_MODELVIEW_MATRIX, (GLfloat *)tb_transform); glPopMatrix(); } void tbIdle() { tb_angle+=tb_inc_angle; } void tbMatrix() { assert(tb_button != -1); glRotatef(tb_angle, tb_axis[0], tb_axis[1], tb_axis[2]); glMultMatrixf((GLfloat *)tb_transform); } void tbReshape(int width, int height) { assert(tb_button != -1); tb_width = width; tb_height = height; } void tbMouse(int button, int state, int x, int y) { assert(tb_button != -1); if (state == GLUT_DOWN && button == tb_button) _tbStartMotion(x, y, button, glutGet(GLUT_ELAPSED_TIME)); else if (state == GLUT_UP && button == tb_button) _tbStopMotion(button, glutGet(GLUT_ELAPSED_TIME)); } void tbMotion(int x, int y) { GLfloat current_position[3], dx, dy, dz; assert(tb_button != -1); if (tb_tracking == GL_FALSE) return; _tbPointToVector(x, y, tb_width, tb_height, current_position); /* calculate the angle to rotate by (directly proportional to the length of the mouse movement */ dx = current_position[0] - tb_lastposition[0]; dy = current_position[1] - tb_lastposition[1]; dz = current_position[2] - tb_lastposition[2]; tb_angle = 90.0 * sqrt(dx * dx + dy * dy + dz * dz); /* calculate the axis of rotation (cross product) */ tb_axis[0] = tb_lastposition[1] * current_position[2] - tb_lastposition[2] * current_position[1]; tb_axis[1] = tb_lastposition[2] * current_position[0] - tb_lastposition[0] * current_position[2]; tb_axis[2] = tb_lastposition[0] * current_position[1] - tb_lastposition[1] * current_position[0]; // tb_lasttime = glutGet(GLUT_ELAPSED_TIME); /* // reset for next time tb_lastposition[0] = current_position[0]; tb_lastposition[1] = current_position[1]; tb_lastposition[2] = current_position[2]; */ /* remember to draw new position */ glutPostRedisplay(); }