1. Viewing and Navigating using OpenGL

2. The LookAt Function Can concatenate with modeling transformations
The GLU library contains the function gluLookAt to form the required modelview matrix through a simple interface
Note the need for setting an up direction
Still need to initialize
Can concatenate with modeling transformations
Example: isometric view of cube aligned with axes
glMatrixMode(GL_MODELVIEW):
glLoadIdentity();
gluLookAt(1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0., );

3. gluLookAt
glLookAt(eyex, eyey, eyez, atx, aty, atz, upx, upy, upz)

4. Outside-In Viewing
Object is centered. Observer navigates on a sphere surrounding the object.

5. Inside-Out Viewing
Viewer centered. Observer navigates, looks toward a point
On the sphere. Sphere center moves with observer.

6. Inside-Out Viewing
Viewer centered. Observer navigates, looks toward a point
On the sphere. Sphere center moves with observer.

7. Some Spherical Geometryx y z
(x,y,z) r q f

8. Viewing: Outside-In x y z
(x,y,z)
gluLookAt(x,y,z,0,0,0,0,1,0);

9. Outside In Viewing Sample Code
glLoadIdentity(); // start with an identity in the MODELVIEW transformation
x = radius * cos(theta) * cos(phi);
y = radius * sin(theta);
z = -radius * cos(theta)* sin(phi);
gluLookAt(x,y,z,0,0,0,0,1,0); //multiply viewing component of transformation
glutSolidTeapot(1.0); // draw what is being looked at (around origin)

10. Viewing: Outside In Possible Navigation Key Mapping
GLUT_KEY_LEFT increase phi
GLUT_KEY_RIGHT decrease phi
GLUT_KEY_UP increase theta
GLUT_KEY_DOWN decrease theta
GLUT_KEY_PAGE_UP increase radius
GLUT_KEY_PAGE_DOWN decrease radius

11. Viewing: Inside Out, from Originx y z
(x,y,z)
gluLookAt(0,0,0,x,y,z,0,1,0);

12. Viewing: Inside Out, from Arbitrary PointX’ Y’ z’
(x,y,z)
gluLookAt(x0,y0,z0,x,y,z,0,1,0);

13. Inside Out Viewing Sample Code
glLoadIdentity(); // start with an identity in the MODELVIEW transformation
x = radius * cos(theta) * cos(phi);
y = radius * sin(theta);
z = -radius * cos(theta)* sin(phi);
gluLookAt(xo,yo,zo,xo+x,yo+y,zo+z,0,1,0); //multiply viewing transformation
glutSolidTeapot(1.0);

14. Viewing: Inside Out Possible Navigation Key Mapping
GLUT_KEY_LEFT increase phi (look left)
GLUT_KEY_RIGHT decrease phi (look right)
GLUT_KEY_UP increase theta (look up)
GLUT_KEY_DOWN decrease theta (look down)
GLUT_KEY_PAGE_UP walk in direction of view
GLUT_KEY_PAGE_DOWN walk away from direction of view