CS559 Spring 2001: Project 3

A Model Railroad

Due Date: 5pm Friday May 11

Project Source Code

New Hint: You are free to change the existing program in any way you like. Change the textures, move the tracks (the train follows them), change the OpenGl settings.

The Basic Task

Like project 1, this project defines a set of sub-goals with points awarded for each goal. Unlike project 1, the goals are far more loosely defined, so there is scope to try interesting things to get all the points available.

You may work in pairs. If you choose to work in a pair, then each member of the pair will get half of the earned points. Once again the maximum number of points, per person, is 100, but there are well over 200 points available. To submit as a pair, one person submits the code and both people submit a readme saying who they are working with.

The Tasks

Texture Mapped Polygon Modeling Max 50 points

Add one or more texture mapped polygon objects to the environment. For example, add some houses with peaked roofs and texture maps for the doors, windows and roof shingles. Other objects are encouraged. Points will be awarded for successful use of texture maps and the complexity of the models (without using outrageous numbers of polygons).

The Train Max 50 points

Make the train a train. The train you design must have some animated pieces, including wheels that go around at the right speed. The train must continue to move around the track and must continue to be aligned with the track, as the existing box is. Clearly, you should get rid of the box. You can only get all 50 points if you have rotating wheels and at least two other animated pieces. Be warned, carriages are hard.

Bezier Surfaces Max 50 points

Add something made of Bezier patches to the environment. Possibilities include but are not limited to silos, round roofed barns, or the boiler on a steam train. You are not allowed to cheat and use the OpenGL Bezier functions, but that limits you to 40 of the 50 points. You must do subdivision to get all 50 points, and you must have multiple patches joined with C1 continuity.

Fractal mounds Max 50 points

Add some mounds, or something else (a garbage heap) modeled as fractal terrains. They must be texture mapped to get all 50 points. Be careful not to disturb the train tracks, although if you really really want to impress me then make the tracks go over the mounds.

L-system Trees Max 50 points

Add some trees or plants defined by L-systems. To keep the polygon count low these will have to be very simple. Maybe pretend it's winter, which means you can do fractal snow drifts instead of fractal mounds (see above).

Change the Navigation System Max 50 points

The navigation system now is not great. Change it to something better. To get all 50 points, you must have a mode where the viewer rides the train.

The Program Skeleton

• Back-face culling is turned on, so face with normals that point away from the viewer will not be drawn. Polygon vertex order is used to determine that normal, so you must always order polygon vertices counter-clockwise about the outward-pointing normal.
• One light is defined and turned on. It is a directional light source with no specular component, so do not define specular components for your models. The light is coming in at an angle, so all the faces of an upright box have different shades. With lighting turned on, you must specify normal vectors for all your objects. (Actually, you could locally turn lighting off, but it would look weird).
• Normalization of normals is turned off. So you must supply unit normal vectors or lighting will not work correctly.
• Texture mapping is used for the ground plane. In particular, it uses mipmapping and a targa image. You do not have to use either of these features with your own texture mapping, but for anything other than the simplest textures, it is probably sensible (and you can copy the code).

The Interface

Hints and Suggestions

• Have fun and be inventive.
• A key thing to consider is polygon count. Graphics hardware can only display so many polygons in a second, and if you try to display too many the frame rate will collapse. Texture maps also use memory, so too many textures can even more dramatically affect performance. To keep polygon counts down, allow larger errors in curve subdivisions, and avoid lots of complex terrain or L-systems.
• The way the train alignment is set up, it is simplest to do just a locomotive, and a short one at that. Doing a long locomotive and having it look like it's following the track is quite difficult. Doing carriages and having them follow at a constant distance and follow the track is even harder.
• Make use of the OpenGL error checking mechanism. It is described in the red book.
• Start simple - just try to get a polygon to appear in the center of the world.
• The way the current train transformations are set up, the origin for the train is assumed to be at the bottom (at track level) and between the two rails.
• It is OK to have multiple modeling techniques in one object. For instance, you could have a train made up of some texture mapped polygons with some Bezier patches, and animated in a hierarchical fashion. You get all the points if you do a sufficient amount of each technique.
• It is OK to borrow code from other sources - but not other students. You will probably learn as much trying to figure out how someone else's code works as you would doing it yourself.
• Texture images abound on the web, so feel free to use them. Or you can use a program like Photoshop to create your own. You might even find a use for the first project.

Example Program

• Polygon mesh houses, and polygon mesh pieces for the train. The houses are texture mapped.
• An animated train with wheels that go around and connecting rods.
• Fractal terrain hillsides.
• Bezier patches for the barn roof and the silos, with the silos demonstrating continuity (first order). Each silo is made up of 8 patches. The barn roof is a single patch, and the barn walls at each end are also patches, so that they meet the roof correctly.
• If you hit the "t" key then you start to ride the train. Hitting "t" again puts you back where you were before.

It does not demonstrate L-systems. This program would be good for about 225 points. It should do more for the view change (such as a "walk" mode) and would need to do L-systems to get the full 300 points.