MUSCLE SIMULATION
A Personal Exploration of Houdini’s Muscle System
This project was a deep dive into Houdini’s muscle system—a fascinating journey, particularly because online resources on this topic were scarce at the time. Driven by curiosity and determination, I embarked on a process of extensive research and trial-and-error to create something robust and functional.
The challenge I set for myself was to manage the entire workflow independently: sculpting, retopologizing, texturing, and rigging a Deathclaw—a creature inspired by my love for the Fallout universe. It felt like the perfect subject for such an ambitious project. After sculpting and rigging, I animated the Deathclaw in Blender before importing it into Houdini for the muscle simulation.
To achieve realistic results, I constructed an internal skeleton and muscle anatomy for the Deathclaw. Once imported into Houdini, the animation’s capture attributes were transferred to the skeleton, which became the foundation for the muscle simulation. The workflow followed a layered approach: the skeleton drove the muscle simulation, the muscles in turn drove the fascia simulation (the connective tissue between the skin and muscles), and finally, the fascia simulation drove the skin simulation.
This layered approach brought the Deathclaw to life with remarkable detail and realism. It was an exciting and rewarding exploration of Houdini’s potential, pushing me to expand my skills and problem-solve creatively.
The First Stage, Base animation. This can be achieved using either a point deform or transferring over the BoneCapture attributes from the Imported Animation unto the Skeleton. From there, just using a BoneDeform, you can bring back the original animation but with your skeleton instead.
SECOND STAGE: the first simulation. muscles are attached to the bone using proximity constraints and muscle to muscle constraints. this phase can be iterative as one needs to go through many setting in order for the muscles to contract properly. This can be further automated using muscle tension lines that pick up when the muscle contracts or extends.
THIRD STAGE: Second simulation, the facia. in order to create proper realistic movement of the skin, there is an intermediary simulation called the facia that simulates the tissue sliding and contracting in between the muscles and the skin.
FOURTH AND FINAL STAGE: the Skin simulation. the facia simulation is then used to drive the simulation of the skin to create an added layer of realism. In some cases, the facia stage can be skipped, but for close ups it is definitely important to have. the final result is then blended in with the original animation to create the final result.
I personally managed every aspect of this project, from conceptualization and execution to modeling, rigging, texturing, VFX, lighting, post-production, and editing.