Surface and Volumetric
Data Rendering and
Visualization
LAB: Moving the camera
Massimo Mauro
Department of Information Engineering
Faculty of Engineering
University of Brescia
Via Branze, 38 – 25231 Brescia - ITALY
Sergio
©
2012Benini
S. Benini, M.Mauro
Università degli Studi di Brescia - S. Benini - 2011/12
1
Contents

Moving the camera with the keyboard

Moving the camera with the mouse
Sergio
©
2012Benini
S. Benini, M.Mauro
Università degli Studi di Brescia - S. Benini - 2011/12
2
Moving camera with the keyboard

Moving our system with the keyboard is quite simple.

We want to rotate left/right and up/down with arrows, and we want to zoom
in/zoom out with '+/-'.

For the zoom, glutKeyboardFunc is good.

For the rotation, it isn't, because the arrows are special keys (they don't
have an ASCII code). We need to use glutSpecialFunction, and use
constants (predefined in glut.h) GLUT_KEY_LEFT, GLUT_KEY_RIGHT,
GLUT_KEY_UP, GLUT_KEY_DOWN.
Sergio
©
2012Benini
S. Benini, M.Mauro
Università degli Studi di Brescia - S. Benini - 2011/12
3
Moving camera with the keyboard
/Keyboard Zoom and Exit
void handleKeypress(unsigned char key, int x,
int y) {
switch (key) {
//Keyboard Rotation
void handleSpecialKeypress(int key, int x,
int y) {
switch (key) {
case 27: //Escape key
exit(0);
break;
case GLUT_KEY_LEFT:
_angleY+=2.0;
glutPostRedisplay();
break;
case '+':
_zTranslate+=0.25;
glutPostRedisplay();
break;
case GLUT_KEY_RIGHT:
_angleY-=2.0;
glutPostRedisplay();
break;
case '-':
_zTranslate-=0.25;
glutPostRedisplay();
break;
case GLUT_KEY_UP:
_angleX+=2.0;
glutPostRedisplay();
break;
}
}
case GLUT_KEY_DOWN:
_angleX-=2.0;
glutPostRedisplay();
break;
}
}
Sergio
©
2012Benini
S. Benini, M.Mauro
Università degli Studi di Brescia - S. Benini - 2011/12
4
Moving camera with the mouse

Moving our system with the mouse is a bit more tricky.

Two functions are needed:
–
glutMouseFunc detects which mouse button has been clicked, his state
(pressed or released), and the click position.
–
glutMotionFunc detects active mouse motion, i.e. motion that is done while
pressing a mouse button.

We might want to implement zoom with mouse wheel. Unfortunately, GLUT
doesn't have a simple and platform-independent way to handle mouse
wheel.

We will implement the zoom with 'CTRL+Moving Down' for the zoom in and
'CTRL+Moving Up' for the zoom out.
–
glutGetModifiers will detect the 'CTRL' button.
Sergio
©
2012Benini
S. Benini, M.Mauro
Università degli Studi di Brescia - S. Benini - 2011/12
5
Moving camera with the mouse
//Mouse click detection
void handleMouseClick(int button, int state, int x,
int y) {
//Mouse moving for rotation and zoom
void handleMouseMove(int x, int y) {
int mod = glutGetModifiers();
if(button == GLUT_LEFT_BUTTON) {
if(dragging&&mod!=GLUT_ACTIVE_CTRL) {
_angleX += (y - drag_y_origin)*0.2;
_angleY += (x - drag_x_origin)*0.2;
drag_x_origin = x;
drag_y_origin = y;
}
else if(dragging&&mod==GLUT_ACTIVE_CTRL){
_zTranslate+=(y - drag_y_origin)*0.02;
drag_y_origin = y;
}
if(state == GLUT_DOWN) {
dragging = 1;
drag_x_origin = x;
drag_y_origin = y;
}
}
}
glutPostRedisplay();
}
Sergio
©
2012Benini
S. Benini, M.Mauro
Università degli Studi di Brescia - S. Benini - 2011/12
6