The model was rendered entirely in Houdini to test out Karma and Solaris.
3D Artist Milen Piskuliyski has unveiled a 3D recreation of Tony Ferguson, a.k.a El Cucuy, an American professional MMA fighter. According to the artist, the goal of the project was to study likeness, with Tony having been chosen for his very particular facial features. The project's description states that the character was made using ZBrush, Substance 3D Painter, Maya, Nuke, and Texturing XYZ's materials and rendered entirely in Houdini to test out its Karma and Solaris tools.
And here are the references used by the artist:
You can check out more of Milen's amazing projects here.