# Elastic 666 test

## Test scenario

- Perfectly elastic collision (restitutional coefficient = 1)
- Zero friction
- 6 x 6 x 6 number of 10 kg spheres
- Small perturbation in position to collapse
- Metric: system energy

## Tested solver list

- Rai
- Bisection solver (Rai solver)

- Bullet
- Sequence impulse

- ODE
- Dantzig
- LCP PGS

~~MuJoCo~~^{[1]}- PGS
- CG
- Newton

- Dart
- Dantzig
- LCP PGS
^{[2]}

### Commentary

- [1] Elastic collision cannot be simulated in MuJoCo. See Bouncing test page for more details.
- [2] Dart LCP PGS fails with timestep > 0.01: the simulation is blown up. We only report the results with timestep < 0.01 for LCP PGS.

## Results

With the same test setup with 666 test, but for elastic collision, we investigated the energy of the system. The result is as follows:

The RaiSim has good energy preservability and also fast contact simulation for the elastic collision of primitive shape objects.