Prerequisite:

pip3 install taichi

python3 linear_fem_minimal.py

python3 linear_fem_invertible.py

This script includes the implementation of

1. Invertible corotated constitutive model. From the paper "Energetically Consistent Invertible Elasticity".
2. Invertible neo-hookean constitutive model. From the paper "Stable Neo-Hookean Flesh Simulation".

This script uses the invertible neo-hookean model by default. Modify CONSTITUTIVE_MODEL=INVERTIBLE_COROTATED in code to use the invertible coroated model.

The results of the two models are shown as follows:

Invertible Corotated	Invertible Neo-Hookean

The SIGGRAPH course "Dynamic Deformables: Implementation and Production Practicalities" is an excellent article. However, there are some typos in the derivation of the invertible neo-hookean model, which could lead to misunderstandings. We have tried to correct these mistakes, and you can find more details here: A Derivation of Stable Neo-Hookean Constitutive Model.