  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.
