The Purge Mask Materialized

A dark and abstract creation of the mask used in The Purge.

I was glad to join Bigstar to help create this promo for The Purge. I worked on R&D, look dev, styleframes, and created the mask materialization effect using Houdini. The final was rendered by the talented folks at Bigstar in C4D using Octane.

We really pushed the connection between Houdini and Cinema 4D on this one. The mask build / materialization effect was created using VDB techniques. Since C4D didn't have VDB processing capabilities at that time, I meshed the VDBs in Houdini and baked the polys to alembic, being careful to maintain the original mask shape, UVs, normals, and fine details.

For my FX work, a workflow issue came up with alembic because it writes a single, sometimes huge file. That was a problem for this spot because the mask was dense 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 positions, normals, and UVs adds up to a massive file depending on the shot length. I was initially culling the polys by the camera frustum but we were making camera changes often so I ditched that early on.

For an average shot the FX cache file was about 60 gigabytes, which was no problem to use (although viewport movement was but a fevered dream in C4D). The largest file exceeded 250 gigabytes, which was a problem for the network and produced some interesting errors. That particular file 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.