We are currently reworking the way wheels interact with their surroundings in The Bus. The previous systems are being replaced by the new 3D Collision System, which can detect obstacles around the wheel more reliably.
Note on the screenshots shown
For the screenshots shown, we illustrated the systems using a bus from Fernbus Simulator. However, the new 3D Collision System will initially be used in The Bus.
The previous systems
Previously, the Lateral Collision System and the Longitudinal Collision System were used for this. Both systems worked with a simplified check that started from a point near the center of the wheel and only checked in one dimension whether an obstacle was detected.
Lateral Collision System
The Lateral Collision System was responsible for side contacts. If a wheel was close to an obstacle, it could happen that the obstacle was not detected correctly at first. Instead, the road surface was often registered. As a result, the wheel visibly penetrated the obstacle without the suspension reacting to it. This was especially unrealistic for obstacles positioned to the side of the wheel.
Longitudinal Collision System
The Longitudinal Collision System worked in a similar way, but for obstacles in front of or behind the wheel. When the vehicle approached an obstacle from the front, the wheel could also detect the obstacle too late. In certain situations, the check still only detected the road surface, even though the obstacle was already directly in front of the wheel. As a result, the wheel could also penetrate the obstacle without the suspension being triggered correctly.
The shared problem
In both cases, the problem was that the position of the obstacle was calculated using only a simple line from the area near the center of the wheel. This meant that the obstacle was only detected once the center of the wheel was exactly at the surface or had already passed it. In other words, the system reacted too late.
The new 3D Collision System
With the new 3D Collision System, we are solving exactly this problem. The new solution combines the previously separate approaches of Lateral Collision and Longitudinal Collision and now checks the area around the wheel in three dimensions. As a result, obstacles are no longer detected in only one direction, but throughout the relevant area around the wheel.
As soon as an obstacle is detected by the 3D Collision System, the vehicle reacts accordingly. The wheels no longer penetrate obstacles unnaturally, but can detect them earlier and respond to them in a more predictable way.
This becomes especially visible during side contacts with the environment, for example when the vehicle drives close along a boundary. If you drive parallel to an edge, the wheel now follows the actual shape of the tire much more closely thanks to the new system. As a result, it runs along the edge instead of sliding over it unnaturally or penetrating the boundary.
The new 3D Collision System can also react earlier and more accurately to obstacles in front of or behind the wheel. This means that a reaction is no longer triggered only once the center of the wheel has already reached or passed the obstacle. Instead, the area around the wheel is taken into account.
When the system reacts
If an obstacle is close to the wheel but still outside the relevant collision area, the suspension remains unchanged. Only once the obstacle reaches this area does the 3D Collision System take effect.
What this improves
With the new 3D Collision System, the check is no longer based on a single line from the wheel. Instead, the relevant area around the wheel is taken into account. In the video, we illustrate how the system detects obstacles, height differences, and sloped surfaces more accurately, and how this improves the way the wheels react in many situations.
The system shown is still in development and is not final. We will keep you updated and continue to share further insights into the ongoing work on The Bus.
