Week 3

This week's program animates the robot so that its legs move as if walking and its entire body is translated in the direction its walking. Pressing the arrow keys rotate the robot and change its direction.

I had problems setting the perspective projection. Right now the program uses an orthographic projection, which means that more distant objects do not appear smaller. Perspective projections, which use a pyramid-like object called a frustum to make projections, are more realistic because distant objects look smaller, while closer objects look bigger. When I used gluPerspective to set the frustum, I couldn't find values for the field-of-view angle, near distance, and far distance that would project the robot to a reasonable size.

Right now I'm still using orthographic projections, so when the robot walks toward the viewer, it doesn't look bigger as it approaches.

In last week's program, it seemed that the light followed the robot around so that the same face was always lit. It seems that this might be because of the way normals are set up. I used gluSolidCube to draw the robot's parts, so the normals were already set in that built-in function. In the next few days I'll try redrawing the cubes with polygons and setting my own normals to see if that problem is fixed.

May 2, 2003 Update

I have posted a new version of the program as week3-2.tar.gz. The robot is now drawn by using quads to form cubes that are then scaled. The normals are set manually so that now the lighting is correct. When the robot rotates, surfaces are lit or dimmened depending on their position. The projection used is now an perspective projection. When the robot walks towards or away from the viewer, it now changes size depending on the distance between it and the viewer. It turned out that earlier problems with using gluPerspective had been caused by reloading the identity matrix in the Robot::setup() method.

Original week 3 files (.tar.gz format)
New week 3 files (.tar.gz format)

Last modified: May 2, 2003 3:28:14 PM PST