Hey guys, VFX and UI artist for Pyre here. Just got an email pointing me to the thread. First time here - what a cool forum, lots of inspiring work.
Anyway looks like you guys are pretty close! I actually did the fluid sim in Maya, and used SOuP tools’ upres fluid to get the additional wavelet turbulence detail. Then indeed output to a mesh and assigned vertex colors using a ramp based on the fluid sim temperature. Mesh turned out to be more useful than voxel for this effect because it allowed some additional deformations (twist, FFD) to push the shape closer to the concept art, as well as providing nice clean edges. To achieve the loop I just crossfaded the fluid cache.
Rendered to exr with some other properties that seemed useful: z-depth, normal, AO, motion vector, and did the rest of the compositing in After Effects with additional gradients, noise masks, glows, some distortion and additional particles.
Each team in the game has a primary and secondary color represented in their Pyre; the secondary color is represented in the smaller “core” of it, which was a separate fluid sim but voxel rendered instead of mesh.