I was glad to join Bigstar to help create these promos for The Purge. For the mask materialization spot, I worked on R&D, look dev, styleframes, and created the mask materialization effect using SideFX Houdini. For the emblem melting spot, I worked on the melting effects and did some compositing.
We really challenged the connection between Houdini and Cinema 4D for these spots. The mask build materialization effect was created in Houdini using mainly VDB techniques while the melting effects were a combination of high viscosity FLIP simulations, soft body simulations, and VDB processing through SOP solvers. The final renders were done in Cinema4D by the talented team at Bigstar and since C4D didn't have VDB processing capabilities at that time, I meshed the VDBs in Houdini and baked the polys to alembic. During the conversion to a poly mesh, I was careful to maintain the original mask shape, UVs, normals, and fine details. Normally, trading poly geo between software is simple using the alembic file format but a major workflow issue of alembic is that it writes to a single, often huge file. That was an issue for this spot because the mask model was quite dense even before the effects so once I added the internal volume information, fine detailed line connections, and brought those to close-up detail poly conversion, we were looking at well over 60 million vertices per frame. That many vertices carrying data for position, normals, and UVs adds up to a massive file depending on the shot length. For one shot the FX cache file was about 60 gigabytes, which was actually no problem to use (although viewport movement was but a fevered dream in C4D). At the peak, we had a single ABC file exceeding 250 gigabytes, which was a serious network transfer problem and produced some interesting errors. That particular file eventually had to be transferred using SSDs. For transferring large amounts of data like this in the future, I'll build a bgeo loader in C4D instead to avoid such large files. I love a technical challenge so I was glad to come across these issues and I learned a lot.