Rigs of Rods ("RoR") is an open source, freeware, multi-simulation game which uses soft-body physics to simulate the motion and deformation of trucks. The game is built using a specific soft-body physics engine called Beam, which simulates a network of interconnected nodes (forming the chassis and the wheels) and gives the ability to simulate deformable objects. With this engine, trucks flex and deform as you ride the terrain, which can be based on real terrain elevation data. Crashing into walls or terrain can permanently deform a vehicle.