BRL-CAD provides several ways to model 3D geometry including a graphical tool named mged, another named archer, and various ways to create geometry using scripts. We use 3D models for development and to showcase our features. You can learn the basics of 3D modeling in just an hour or two using our tutorial documentation.

If you haven't yet noticed, our project logo looks a lot like a gear or a couple bicycle chain links. We want you to model an actual bicycle chain with 2-to-10 links.

Model accurate bicycle chain links using the below references. Your job is to model it natively using any of BRL-CAD's tools (i.e., don't model it in something else, don't import anything).

The model should have regions defined for each part (each separate piece of metal becomes it's own region) and no overlaps (use rtcheck and/or gqa commands to verify). Create one top-level combination to group everything together.

Submit a text file or comment describing any resources or web links you used in making your chain and describe your model.

• http://en.wikipedia.org/wiki/Bicycle_chain
• http://upload.wikimedia.org/wikipedia/commons/b/b0/Rollenketting.gif
• http://pardo.net/bike/pic/fail-004/000.html
• https://www.google.com/search?q=bicycle+chain&tbm=isch
• https://www.google.com/search?q=bicycle+link&tbm=isch
• https://www.google.com/search?q=bicycle+drawing&tbm=isch

• Submit your model as a .g file (BRL-CAD's geometry file format) and a rendered PNG image. You can run "rt -s1024 -o your_rendering.png your_geometry.g your_top_level_object" to create a PNG rendering of your model.