Fixing the Vehicle class in UE4 starting with NWheel implementation.

[BoredEngineer]

@seandennis;442377

Its good to see someone looking into this. I’ve gone through the other threads and downloads and even though everyone has done some great work. I can’t find what I am looking for as I am not a coder but I can read it and understand it, but doing it is another matter.

First of all, my family has been building racecars for over 30 years. we specialize in dirt speedway.

I wasn’t happy with the car physics in UE4, looking at the code it seems that the springs only apply force in 1 direction (down to the ground) but coil springs and even torsion springs (swaybar) work in 2 directions, constantly trying to return to equilibrium. So there is a at rest state, max compression and max extension or a torsion spring is at rest state, negative max rotation and positive max rotation.

Also shock absorber, I noticed that the engine only uses damping in the up direction. but in reality a shock absorber works in 2 directions as you know compression and rebound. but some may not know that shocks also work at low speed and high speed (speed of velocity) the lower the velocity the lower the damping and the higher the velocity the higher the damping. But also shock absorbers can also produce a force, so if the compression force (damping a up velocity) is higher then the rebound force (damping a down velocity) it will push the car up (like you see with monster trucks) but the same is also the other way too. This is used in motor racing to help with car handling. lets say you have a nascar and because you are always turning left the weight of the car always moves to the right, you could either put a shock on the right side with a higher compression force to help it from transferring weight to the right too fast, or you could put a higher rebound force on the left to hold the car to the left to slow the weight transferring too fast. But that is only one benefit of a shock other then damping, I won’t get into pre-loading the spring.

In my opinion if your able to get the suspension to have a rebound and compression settings that would fix a lot of problems that I am seeing with it. I did notice that in Jacky’s threat, he had to set his damper to a negative number to get any reasonable handling.

Funnily enough just made a post about this
https://forums.unrealengine.com/showthread.php?83483-ASSETS-OPEN-SOURCE-Tanks-tracks-and-N-wheeled-vehicles&p=442419&viewfull=1#post442419

I wouldn’t jump too fast to conclusions, if you check PhysX documentation, there are plenty of settings just for suspension. It’s coded by smart people and I don’t think that they didn’t implemented these features due to the lack of skill or knowledge, most likely they are already there and we simply don’t know what kind of other problems have to be solved and how more complicated suspension would help with it.
One of the main issue with raytraced suspension is that unsprung mass is not simulated, there is no collision body with own inertia and it doesn’t slam into chassis when suspension is fully compressed. I’m working on this feature myself and so far, the only solution is to have a collision body on unsprung mass. But this leads to a **** ton of other problems, like collision issue with landscape and stability of joints. Perhaps they stick to raytraced wheel simply to avoid more problems than using proper collision actually solves.