Accurate frictional contact is critical in simulating the assembly of rod-like structures in the practical world, such as knots, hairs, flagella, and more. Due to their high geometric nonlinearity and elasticity, rod-on-rod contact remains a challenging problem tackled by researchers in both computational mechanics and computer graphics. Typically, frictional contact is regarded as constraints for the equations of motions of a system. Such constraints are often computed independently at every time step in a dynamic simulation, thus slowing down the simulation and possibly introducing numerical convergence issues. This paper proposes a fully implicit penalty-based frictional contact method, Implicit Contact Model (IMC), that efficiently and robustly captures accurate frictional contact responses. We showcase our algorithm's performance in achieving visually realistic results for the challenging and novel contact scenario of flagella bundling in fluid medium, a significant phenomenon in biology that motivates novel engineering applications in soft robotics. In addition to this, we offer a side-by-side comparison with Incremental Potential Contact (IPC), a state-of-the-art contact handling algorithm. We show that IMC possesses comparable performance to IPC while converging at a faster rate.

翻译：准确的摩擦接触对于模拟真实世界中杆状结构的组装（如结、毛发、鞭毛等）至关重要。由于杆件具有高几何非线性和弹性，杆-杆接触仍然是计算力学和计算机图形学研究者们面临的一个具有挑战性的问题。通常，摩擦接触被视为系统运动方程的约束条件。在动态模拟中，这些约束通常在每个时间步独立计算，从而减慢了模拟速度，并可能引入数值收敛问题。本文提出了一种完全隐式的基于惩罚的摩擦接触方法——隐式接触模型（IMC），能够高效且稳健地捕捉准确的摩擦接触响应。我们展示了该算法在实现视觉真实感结果方面的性能，特别针对流体介质中鞭毛束聚这一具有挑战性且新颖的接触场景——这是生物学中的一个重要现象，并启发了软体机器人学中的新颖工程应用。此外，我们与当前最先进的接触处理算法——增量势接触（IPC）进行了并排比较。结果表明，IMC在拥有与IPC相当性能的同时，收敛速度更快。