From Rigs of Rods Wiki
Rigs of Rods (RoR) is not your typical vehicle simulator. Other vehicle simulators use fake suspension, mesh-based vehicles with no mass distribution, predetermined damage from collisions, and approximated fuzzy-dice sway models.
RoR does not do this. In RoR, all vehicles are based on only two elements: Nodes and Beams. Using these nodes and beams, an almost infinite variety of vehicles and contraptions can be constructed. For instance, real world suspension can be created using these nodes and beams. Through the use of Flexbodies, realistic vehicles with dynamic deformation can be created. And with some extremely simple node/beam magic, fuzzy dice can be made to sway exactly as in real life.
So what are these nodes and beams, then?
Nodes are essentially zero-dimensional ball joints. They occupy no space, but they do have mass. By themselves they can do very little. They exist to provide beams with two points to connect. (They also control collision, but we'll get into that later.)
Beams are the visible connections between nodes. Beams do not have any mass and do not interact with anything but the two nodes they are connected to. Beams can stretch, compress, and break based on the forces applied to them. The initial length of a beam is the space between two nodes. As a vehicle moves and flexes, the movement of these two nodes forms the force against the beams.
If you have ever played that old game Pontifex, you should be familiar with these concepts.
This is, of course, not a perfect simulation, and there are some issues with it.
- Much like atoms, nodes are constantly in movement. Nodes in RoR behave much like atoms in a solid. They are generally in a fixed position, but tend to vibrate. In normal conditions and situations, we do not notice atoms vibrating due to the scale. However, nodes in RoR tend to vibrate noticeably. As a consequence, vehicles will sometimes move around a bit with no input. (This is less noticeable with heavier vehicles).
- Because nodes occupy no space, they tend to exert a high amount of force to a small surface area. Consequently, nodes tend to penetrate a face rather easily. This issue is currently being addressed.
- Nodes act as ball joints to the beams that are connected to them. In order to get any kind of coherent and stable structure out of them, it is necessary to use a lot of triangles.