Rigid Body Cable for Virtual Environments

Abstract

The present paper addresses real-time simulation of cables for virtual environments. A faithful physical model based on constrained rigid bodies is introduced and discretized. The performance and stability of the numerical method are analyzed in details and found to meet the requirements of interactive heavy hoisting simulations. The physical model is well behaved in the limit of infinite stiffness as well as in the elastic regime, and the tuning parameters correspond directly to conventional material constants. The integration scheme mixes the well known Störmer-Verlet method for the dynamics equations with the linearly implicit Euler method for the constraint equations and enables physical constraint relaxation and stabilization terms. The technique is shown to have superior numerical stability properties in comparison with either chain link systems, or spring and damper models. Experimental results are presented to show that the method results in stable, real-time simulations. Stability persists for moderately large fixed integration step of Delta t = 1/60 s, with hoisting loads of up to 10(5) times heavier than the elements of the cable. Further numerical experiments validating the physical model are also presented.

Hybrid, Multiresolution Wires with Massless Frictional Contacts

“…We introduce stretch and bend viscoelasticity based on conventional material. As was shown in [18] and [19] …”

“…The limit of high resolution is thus associated both with increased computational complexity and requires smaller time steps. In the exploration of rigid multibody chain it was discovered that stability at indefinitely large mass ratios between load and wire can be realized by increasing the bend and twist elasticity of the wire to suppress the high frequency transversal oscillations [18]. The drawback of that approach is the lack of a stable and fast contact method to combine it with.…”

“…This is accomplished by continuously updating the node positions p k according to Eqn. (18). We solve this optimization problem each time step by GaussSeidel iterations over the contact list C. Two iterations in opposite direction have proved sufficient in practice, since the wire configuration is close to optimal from the last time step.…”

Simulation of granular soil behaviour using the Bullet physics library

“…As mentioned before, physics engines are primarily developed for entertainment for games and movies, however, they have been used by researchers for simulations in the fields of robotics (Richard, 2008;Basri et al, 2012) and industrial engineering (Servin & Lacoursiere, 2008) too. But they have been rarely used in the field of civil and geotechnical engineering and even in those rare cases, they were employed merely for visualisation purposes rather than engineering analysis.…”

Particle-based solid for nonsmooth multidomain dynamics

“…This becomes straightforward when the regularisation is introduced by potential energy as quadratic functions in g, i.e. U ε (q) = 1 2 g T ε −1 g. This has been exploited in previous work to constraint-based mod-elling of lumped element beams [29], wires [30], meshfree fluids [31], and granular material [8].…”