This is the Hobak library, which accompanies the SIGGRAPH 2022 Course Dynamic Deformables: Implementation and Production Practicalities (Now With Code!) by Theodore Kim and David Eberle. This library is intended to illustrate many of the concepts from the course as clearly as possible, and as a consequence is currently not optimized for performance. Readers beware: anybody claiming a 5X speed win over this code ain't actually claiming that much.

Hobak is Korean for squash or pumpkin. This is library for squashing things.

Hobak is designed to build and run with the smallest number of dependencies possible. All the necessary external libraries are already included in the HOBAK/ext directory. Hopefully, you will not need to download anything else.

The fastest way to get up and running is to pick a build architecture, and call make on it. From the top level HOBAK directory, to build on Linux, just call make linux. It should put everything where it needs to go, build the simulateScenes project, and run a Bunny Drop simulation.

If you want to build on a Mac, just call make mac. This one might give you a build error saying it can't find GLUT, in which case you need to install XQuartz, because apparently Mac is just toooo goooood to have GLUT installed by default.

If you have a version of g++ installed that supports OpenMP (the default Mac compiler, clang, does not), you can alternatively build everything on the Mac by calling make mac_omp. It will expect that g++ already points to an OpenMP-capable compiler.

To build a project in Hobak, you first need to pick an architecture. If you called make linux or make mac, then it already picked for you.

If you want to pick by hand, go to HOBAK/projects/, and copy one of the include_top files to include_top.mk. For example, to build on Linux, call cp include_top.linux include_top.mk. Again, if you already ran make linux, this was already done for you.

From there, if you want to build a specific project, go to its directory and call make depend, followed by make. For example, to build the regression test suite, do:

cd projects/regressionTests
make depend
make

You only need to call make depend once. It will build the dependency files, i.e. which files depend on which headers. After calling it once, you should only need to call make from then on. You should only need to run make depend again if you change the dependencies, such as adding a new file to the Makefile, or changing a header.

Everything should be run from the ./bin directory. So, to build and run regressionTests, do:

cd projects/regressionTests
make depend
make
cd ../../bin
./regressionTests

Projects that pop up an OpenGL window, like simulateScenes or replayScenes support the following keyboard commands:

• a will start and stop the animation.
• q will quit, and write out a JSON file of simulation data and a QuickTime movie of the animation. You need to have FFMPEG installed for the movie write to succeed.
• Q or Esc will quit without writing anything out.

Some basic unit and regression testing has been implemented using the Catch2 library. The following should build and run the units:

cd projects/unitTests
make depend
make
cd ../../bin
./unitTests

A bunch of features are missing, mostly because my coding time is limited. If you want to see these features implemented, either add them yourself or give me a grant.

• Continuous Collision Detection (CCD) and Global Intersection Analysis (GIA): If something weird happens under violent collisions, e.g. triangles get snagged, this is probably why.

• Line Search: If the simulation explodes, this is probably why.

• Shells and Strands: For now, you can fake it with really thin tet meshes.

Hobak uses the following external libraries, all of which are included in the download, so that we don't run into versioning issues a year from now.

• Eigen
• Catch2
• RapidJSON
• Spectra
• GLVU