1. Class 11 timers Iron Maiden example Double Buffering BallAndTorus
throwBall – incorporating physics
Complex object with moving parts
Viewing Transformations: glLookAt
Cummulative Rotation
Orientation and Euler Angles
selection

2. 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 ...

3. 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.

4. 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);

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

6. 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

7. 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();

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

9. ballAndTorus.cpp
run it.

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

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

12. ballAndTorus.cpp

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

14. 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);

15. 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);

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

17. throwBall.cpp run it. incorporate physics x(t)=h*t
y(t)=v*t - g/2 * t*t
// Apply equations of motion to transform sphere.
glTranslatef(h*t, v*t - (g/2.0)*t*t, 0.0);

18. Using a for loop for circle or time (or even color!)
On the white board
10 points on a circle
10 seconds of a flying ball
50 shades of grey

19. throwBall.cpp note routine to print float to string
also note special key functions
Try out ballAndTorusWithFriction.cpp - more physics

20. Assembling a Clown Head Run clown3.cpp
head radius 2
ear radius 0.5
Hat: height 4
radius 2
Brim: inner radius 0.2
outer radius 2.2
ear to head
0 - 2
Hat sits 2 units
from center of head
Tilted 30o from
vertical

21. clown3.cpp figure out placement of ears
// Transformations of the left ear.
glTranslatef(sin((PI/180.0)*angle), 0.0, 0.0);
glTranslatef(3.5, 0.0, 0.0);
// Transformations of the right ear. glTranslatef(-sin((PI/180.0)*angle), 0.0, 0.0); glTranslatef(-3.5, 0.0, 0.0);

22. clown3.cpp: spring to left ear
// Transformations of the spring to the left ear.
glTranslatef(-2.0, 0.0, 0.0);
glScalef(-1 - sin( (PI/180.0) * angle ), 1.0, 1.0);
// Spring to left ear.
glColor3f(0.0, 1.0, 0.0);
glBegin(GL_LINE_STRIP);
for(t = 0.0; t <= 1.0; t += 0.05)
glVertex3f(t, 0.25 * cos(10.0 * PI * t), 0.25 * sin(10.0 * PI * t));
glEnd();

23. clown3.cpp Study the code. Notice the order of transformations
Notice the use of glPushMatrix() and
glPopMatrix().
Observe how the animation is done.

24. floweringPlant.cpp run uses depth testing
uses 3 sequential display list:
stem segment, sepal, petal

25. Viewing Transformation
gluLookAt( eyex, eyey,eyez,
centerx, centery,centerz,
upx, upy, upz )
eye is where the camera should be
center is where it should be aimed
up determines how we hold the camera

26. gluLookAt( eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz )
Line of Sight ( los) goes through eye and center.
Vertex of pyramid that gives frustum is at eye. Near and Far measured from there.
Line Of Sight runs through center of frustum
"True up" is component of up perpendicular to los.

27. gluLookAt(0.0, 0.0, 0.0, 2.0, 0.0, 5.0, , 1.0, 0.0 ); 2 1 -4 -3 -2 -1 1 2 3 4 -1 -2 -3

28. gluLookAt(0.0, 0.0, 0.0, 2.0, 0.0, 5.0, , 0.0, 0.0 ); 2 1 -4 -3 -2 -1 1 2 3 4 -1 -2 -3

29. gluLookAt(2.0, 1.0, 0.0, 2.0, 0.0, 5.0, , 1.0, 0.0 ); 2 1 -4 -3 -2 -1 1 2 3 4 -1 -2 -3

30. gluLookAt( ); 2 1 -4 -3 -2 -1 1 2 3 4 -1 -2 -3

31. boxWithLookAt.cpp
Run. Just like box, but with gluLookAt instead of glTranslate.

32. clown3.cpp Run. Modify to use gluLookAt instead of glTranslate.
Look from front of sphere, just touching.
What do you see?

33. clown3.cpp Run. Modify to use gluLookAt instead of glTranslate.
Look from front of sphere, just touching.
What do you see?
Have to adjust glFrustum!

34. clown3.cpp Run. Modify to use glLookAt instead of glTranslate.
Look down from well above hat.
What do you want "up" to be?

35. gluLookAt( eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz )
Apply to the MODELVIEW matrix, not the PROJECTION matrix
Code:
Load the MODELVIEW matrix
Set matrix to the identiry
Place your cameral
Build your world using reasonable
world coordinates

36. gluLookAt(eyex, eyey, eyez, centerx, centery, centerz,upx, upy, upz)
move the camera to (eyex, eyey, eyez)
rotate till it is facing the center
rotate about the line of sight till up is in
the right direction.
Is equivalent to moving the surrounding world:
glRotate(B,0,0,1);
glRotate(A, wx, wy, wz);
glTranslate(-eyex, -eyey, -eyez);

37. gluLookAt(eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz)
is equivalent to reverse of:
Translate camera from eye to origin
rotate the camera about the x-axis,
till the line of sight lies on the x-z plane
rotate the camera about the y-axis,
(staying in the x-z plane) till the
line of sight is pointing in the -z direction.
rotate the camera about the line of sight
( = z-axis)
till the top is pointing in the +y direction.

38. The 3 angles from the 3 "rotates" are the Euler angles.

39. Picking and Selection
Run BallAndTorusPicking.cpp to understand the problem.
How computer knows which shape or color to use for drawing.
How can the computer "know" which shape belongs to a pixel to modify?

40. glRenderMode(GL_SELECT)
Selection
Tell computer you will be selecting
glRenderMode(GL_SELECT)
Specify a (new, small) viewing volume
selection volume
Redraw the scene, invisibly, recording which items hit the viewing volume
hit list

41. when hit records are written
A hit record is written into the hit buffer when both
a name stack manipulation or a glRenderMode() command is encountered
a hit has occured - a primitive has been drawn that intersects the selection volume

42. what hit records contain
the number of names in the name stack at the time of writing the record
the min z-value‡ of primitives that hit selection volume since last hit record was written
the max z-value‡ of primitives that hit selection volume since last hit record was written
the sequence of names in the name stack at time of writing, bottom one first, may be none.

43. min and max values ‡
min and max are "normalized" by dividing by depth of selection volume, so value is in range [0,1].
Then multiplied by and stored as an unsigned int.

44. How to PICK the right selection volume?

45. gluPickMatrix(pickX, pickY, width, height, viewport[4])
glLoadIdentity();
gluPickMatrix(pickX, pickY,width,height, viewport[4]);
glFrustrum(); or gluPerspective; or glOrtho; (same as resize function)

46. gluPickMatrix(pickX, pickY, width, height, viewport[4])
pickX and pickY are in gl screen coords.
front face of selection volume is centered at (pickX, pickY) with given width and height. In pixels.
viewport array supplies current viewport boundaries. Can use
glGetIntegerv(GL_VIEWPORT,viewport)

47. ballAndTorusPicking.cpp void drawBallAndTorus(void)
void drawScene(void)
// The mouse callback routine.
void pickFunction(int button, int state, int x, int y)
void findClosestHit(int hits, unsigned int buffer[])
void animate(int value)

48. collision detection Run spaceTravel.cpp
Go through code - non-collision parts
Notice class, constructors
Notice viewports.
Notice display list.
Notice rand.
In setup I added srand(time(0));
Need to include ctime
I also changed FILL_PROBABILITY

49. geometry of the spacecraft
radius 5
height 10
red center to edge of circle
=sqrt(50) = 7.072

50. geometry of collisions

51. collision detection spaceTravel.cpp
static int isCollision = 0; // Is there collision between the spacecraft and an asteroid?
functions:
int checkSpheresIntersection(...)
int asteroidCraftCollision(...)
see specialKeyInput function

52. Articulated Figure On your own, run animateMan.cpp.
Do the experiments in the book.
Come back with questions.

53. simple shadow run ballAndTorusShadowed.cpp
in drawFlyingBallAndTorus see
if(shadow) code.
in drawScene see 2 calls to drawFlyingBallAndTorus
Light is at infinity, directly overhead.