1. Lab 7
Viewing

2. Parallel vs. Perspective Projection
Parallel projection (Orthographic)
glMatrixMode(GL_PROJECTION);
glOrtho(xwmin,xwmax,ywmin,ywmax,dnear,dfar);
Perspective Projection
Two ways to use Perspective Projection:
glMatrixMode(GL_PROJECTION);
gluPerspective(theta,aspect,dnear,dfar); 1
glMatrixMode(GL_PROJECTION);
gluFrustum(left,right,bottom,top,near,far); 2

4. gluLookAt() Function
gluLookAt function: positions and aims the camera towards where the object is drawn.
glLookAt(Xeye, Yeye, Zeye, Xat, Yat, Zat, Xup, Yup,Zup);
glLookAt(0,0,6,0,0,0,0,1,0)
glLookAt(0,0,-6,0,0,0,0,1,0)
glLookAt(6,6,6,0,0,0,0,1,0)

5. glViewport() Function
glViewport() function: it let you choose a smaller drawing region in the window. It is set by default to window’s size.
glViewport(x, y, width, height);
After using viewport to a specific region in the window
Default viewport

6. glViewport() Function

7. Exercise 1 – drawing object twice using viewport
void display(){
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 1.0, 1.0);
glLoadIdentity();
gluLookAt(0.0, 0, 5, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
glViewport(0, 0, 400, 500);
glutWireCube(1);
glViewport(400, 0, 400, 500);
glFlush(); }