Adventures of Prince Achmed, Lotte Reiniger
Hierarchical transformations can be thought of as transformations that are "attached to" other transformations.
They are used to transform objects relative to other objects.
A common use is in articulated bodies.
We can draw this "car" by transforming the two wheels relative to the body of the car.
We'd like each wheel to be affected by the car body's transformation, but not by any other wheel's transformation.
The basic tool needed is commands to save & restore transformation state.
apply body transformation draw body save state apply front wheel transformation draw wheel restore saved state apply rear wheel transformation draw wheel
A transformation is represented mathematically as a matrix.
OpenGL maintains a stack of saved transformation matrices.
glPushMatrix() & glPopMatrix() save and restore transformation state.
Make sure you always have the same number of pushes & pops.
The number of transformations you can save is finite; it is at least 32.
Hierarchical transformations are often represented as a tree of transformations.
This is the basis of scene graph systems.
DUE: Thursday, 6 October 2005, 11:59:59 pm
(via e-mail, to depape@buffalo.edu)
Create a program with lots of motion
The program should use OpenGL geometry (GL_LINES, GL_TRIANGLES, etc)
It can also include images (e.g. a background)
There should be at least 10 shapes; not all of them have to move
The motion can be defined by mathematical formulas, or algorithmically
Try to make the motion complex, but interesting.
Extra credit will be given for interaction - some of the motion
(or other dynamic features, such as color)
responding to user input, in a non-trivial way.
