1. Class 10 Part 1 What values to use for Frustum The Trick
Relative vs Absolute Placement
glPushMatrix glPopMatrix
Animation
glutIdleFunc(increaseAngle)
glutTimerFunc
Double Buffering
Iron Maiden example
BallAndTorus

2. What values to use for glFrustum?
Uses glFrustum(-5.0,5.0,-5.0,5.0,5.0,100.) Picture translated to z=-25

3. -far ?? ? z
right
-near

4. -far ??
far = ??
near right
far * right= ??
near ? z
|z| * right= ?
near
right
-near

5. -far ??
25 * 5 = 25 5 ? z
|z| * right= ?
near
right
-near

6. The Trick - rotating about a general line
MJBrotateOffCenter.cpp
glRect(x1,y1,x2,y2) draws a rectangle, not at the origin. What if we want to rotate it about its center?
The TRICK: move to the origin, rotate, move back.

7. Relative vs Absolute Placement
Case 1: put cube 5 to the right, put sphere 10 above it.(relative)
Case 2: put cube 5 to the right, put sphere 10 above the origin. (absolute)
MJBrelativeVSabsolute.cpp

8. Relative: Prop 4.1
"If object 1 precedes object 2 in the code, the location of object 2 in the local coordinate system of object 1 is determined by the transformation statements between the two and nothing else."
See relative code

9. glPushMatrix(), glPopMatrix
glLoadIdentity();
glTranslatef(0.0, 0.0, -15.0);
glPushMatrix();
glTranslatef(15.0,0.0,0.0);
glutWireCube(5.0);
glPopMatrix();
glTranslatef(0.0,10.0,0.0);
glutWireSphere(4.0,10,10);
I*M1=M1 M1
M1*M2=N2 M1 M1
M1*M3=N3

10. Animation The WRONG way: In the display function:
for (a lot times)
redraw the picture with a minor change
Doesn't allow for interaction.
May not even be redrawn

11. rotatingHelix1.cpp press space increase angle
redraw (once) with the updated angle

12. rotatingHelix2.cpp press space glutIdleFunc(increaseAngle); or
glutIdleFunc(NULL);
registered Idle function: Keep doing that function as long as nothing else is happening.
increaseAngle() says add to the angle and redraw (once).

13. glutIdleFunc(f); registers the function to use while idle.
NULL for don't do anything.
void f(void);
Note functions can be "registered" outside of main, and the registered functions can change.

14. rotatingHelix3.cpp draw picture once
get on line in the event queue for another turn to
add to angle
get on line in the event queue ...
got to here

15. glutTimerFunc(period, timerFunction, value)
put the timerFunction on the event queue period milliseconds from now.
void timerFunction(int value);
value, an input value that will be passed to the timerFunction
value is often not needed so is set to anything.

16. using a timer Main starts the timer function
glutTimerFunc(5, animate, 1);
run the function animate in 5 millisecs.
Have timer function call itself, ie, get in queue again.
At the end of animate have the call
glutTimerFunc(animationPeriod, animate, 1);

17. Go through all of rotatingHelix3.cpp to see how whole process works.

18. Double Buffering front buffer = viewable buffer
back buffer = drawable buffer
Two ring circus:
spotlight on one ring : viewable
in the dark, set up the next act in other ring : drawable

19. Double Buffering - how to
In main,
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); instead of GLUT_SINGLE
Can have one window double buffered and the other single.
at end of display function use
glutSwapBuffers();
instead of glFlush();

20. Iron maiden example maiden project
Nate Robbins gets credit. (Check out, but don't copy, his tutorials.)

21. ballAndTorus.cpp
run it.

22. the Torus
glutWireTorus(2.0, 12.0, 20, 20);
center is the origin.

23. the Sphere
glutWireSphere(2.0, 10, 10);
radius 2
center at the origin

24. ballAndTorus.cpp

25. move the sphere to the right, outside the torus
glTranslatef(20.0, 0.0, 0.0);
glutWireSphere(2.0, 10, 10);

26. rotate sphere about one spot on the torus (revolve about the torus)
"latitudinal rotation"
about the line through (12,0,0), parallel to the y axis
in a circle of radius 8.
on the xz plane.
The TRICK
glTranslatef(12.0, 0.0, 0.0);
glRotatef(latAngle, 0.0, 1.0, 0.0);
glTranslatef(-12.0, 0.0, 0.0);

27. move the sphere in big circle about the torus
"longitudinal rotation"
about the line through (0,0,1), parallel to the z axis
in a circle of radius 20.
on the xy plane.
glRotatef(longAngle, 0.0, 0.0, 1.0);

28. spiral motion about the torus
combine the two motions.