I'm been working on learning the Muscle Solver using the Emil project file provided form Unreal Engine. However, I'm encountering some difficulties with simulating the pectorals (pecs) and deltoids (delts). And solver settings are also posing a challenge.
Pectorals:
I'm experiencing persistent bouncing on the lateral side of the pectoralis muscles (connecting to the humerus bone). Regardless of compression settings (0.0001, 1, 100, 1000), the bouncing persists, especially noticeable during the tissue solve.
The pecs also compress inwards instead of maintaining their outward shape alongside the delts.
Deltoids:
The deltoid clavicular muscle seems to lack stiffness. I've experimented with shape stiffness and mass density values, even increasing density in the delts compared to the pecs to achieve a stronger pull from the delts.
During tight poses, the deltoid clavicular collides excessively with the clavicle bone, even with high compression stiffness values (0.0001 - 10^8). Interestingly, if I manage to resolve the collision issue, the deltoid clavicular then bends inwards unnaturally towards the pectoralis clavicular, which is going back stiffness problem? I'm struggling to understand this behavior.
Muscle Solver Settings:
Vellum Timescale: 500
Gravity: 0
Velocity Damping: 1
I've only been able to get the delts and pecs to work correctly using Emil's pre-saved file cache. When you resave the cache, the results are different (likely due to different settings??). One difference I noticed is the pecs muscle to bone mask setting. In Emil's saved cache, this mask is absent, but when you resave the cache, the mask is added. This addition (and potentially other setting changes and Houdini version changes) seems to prevent the muscles from solving correctly?
Additionally, within the muscle to bone constraints, the damping ratios for the pecs and delts is set to 0.1 instead of the 0.01, this slows the attachments down (my guess is it so relax the pull form the muscle to bone stiffness which I was encountering running the solver in "normal" settings with "normal" settings on the delts and pecs.
I've tried using more "normal" settings for the delts and pecs, such as:
Muscle to Muscle (both delt and pecs): 55
Muscle to Bone (pecs): 0.01
Muscle to Bone (Medial Delt): 5
Muscle to Bone (Anterior Delt - Problem Muscle): 0.01
Muscle to Muscle (Anterior Delt - Problem Muscle): 55
However, with these "normal" solver settings and no velocity damping, the pull from the bone is too strong on the anterior delt. To counteract this, I've resorted to using a higher bone stiffness on the medial delt and lower on anterior delt, along with muscle glue and muscle to muscle attachments (set to 1 and 55) to pull the anterior delt and pecs into position.
Does anyone have any tips on achieving a more realistic and stable simulation for the pecs and delts?
And below I have attached a hip file with the setup copied from the emil solver and the emil cache that works, but in this hip file the save cache also doenst work, it only works in the original hip file with the original cache that comes with the download, not resaved in the hip.
download the zip for the animated bones and original Emil's muscle cache.
Mediafire link to the zip file. [www.mediafire.com]
