CS 184: COMPUTER GRAPHICS

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Lecture #23 -- Mon 4/20/2009.

Warm-up Problem:

Try to make a list of all the different ways in which two rigid components can relate to one another in a kinematic joint.

(Think about the joints in your body or in your car for examples.)

How many degrees of freedom does each of these joints have ?

Remarks on Final Project ( Due May 20, 2009)

In the next few lectures we will briefly discuss some of the suggested extensions to the basic core of your projects.
Most of these extensions will require that you do some research on your own, on the web, or following given references.
(A glimpse of the way you typically do projects in a graduate course.)
You should make up your mind early on, whether to do an modeling/action-based project with standard OpenGL rendering,
or whether you want to focus your attention on advanced (off-line) rendering methods.
I will first discuss two techniques suitable for the first type of project extension,
then spend a couple of lectures on advanced rendering and light/material interactions.

Texture-Mapped Subdivision Surfaces of Arbitrary Genus:
see PPT slides # 27-29:


This is the desired conceptual pattern on a genus-5 cube frame. It serves to set up the texture coordinates so we obtain a pattern that closes nicely around all corners and arms.	This is a more complex polyhedron made of 120 quadrilaterals with adjustable vertex coordinates; this is a good starting point for CC-subdivision with the goal of obtaining a nicely rounded final shape.	This is the kind of final object that we aim for. Little black spheres have been added to the smooth procedurally generated surface. Advanced rendering techniques could be used to add shadows and specualr reflections.

Things to do for the project:

Create a simple winged-edge data structure, and implement the procedure to subdivide the quad faces.
Be aware that several quads may share a vertex, but may want different textures and/or different texture coordinates at that location.

Joints, Articulated Skeletons, Forward and Inverse Kinematics

Types of Kinematic Joints and Linkages

Forward Kinematics

Inverse Kinematics

If you are interested in this topic, see also: a more detailed presentation by Bill Baxter, UNC.

Things to do for the project:
Implement a simple solver for a short chain of kinematic links.
Use such a linked chain as the legs for a walking creature,
or make an interactive demo, where the end of the chain follows a interactively positioned moving target.

Reading Assignments: Whatever gives you the needed background information for your project.

Final Project Due May 20, 2009