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Constraints Are Broken


The video shows the problem well enaugh.

So the problem is as follows:

  • The car has a suspension attached to it with constraint

  • The suspension has wheel attached to it with constraint

And it works. However, this isn't enaugh for front, because I need to steer. So...

  • The car has suspension attached to it with constraint

  • The suspension has steer axle controller(simple physics object - just as any else of them) attached to it with constraint

  • The steer axle controller has a wheel attached to it with constraint

This doesn't work any more. This is the case in video - rear wheels work fine, because they got only 2 constraints each. Front wheels, however, have 3 constraints each, and they don't work any more. This is strange mysterious bug and doesn't make any sense for me(maybe because I'm used to Bullet which didn't seem to have such an issues, or is it not a PhysX, but rather UE4 issue?). I hope that Epic team can solve this bug as soon as possible.

Product Version: UE 4.12
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asked Jul 22 '16 at 10:35 AM in Using UE4

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Hi adriansnetlis,

Physics Constraints are not intended to be used with something as complex as a fully functioning vehicle. We recommend using a skeletal mesh in conjunction with the Wheeled Vehicle Blueprint class.

Here is more info on how that works and also check out the Vehicle and Advanced Vehicle templates in the engine.



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answered Jul 22 '16 at 07:43 PM

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avatar image adriansnetlis Jul 23 '16 at 08:25 AM

Even if they're not meant for that - they still must work. It's OK if the game's code is dirty, broken at some points while it works. But it's not OK if game engine's code is dirty and broken at some points. This is a major bug and must be solved because - there are many things that I expected to use 3-level constraints.
By the way - is it possible to build custom physics via scripting. If I can't do it quick with constraints, I'm gone do it slow way. I hope that it's possible to make something like brush model with air pressure, heat, heat transfer, camber, toe and such things taken in account. I hope that It's possible to do ray-based model.
Note. I am making open-world racing simulator
Greetings, Adrians

avatar image Matt Cohen Jul 25 '16 at 09:29 PM

While my situation/implementation of constraints is far less complex than yours, I found that upgrading to 4.12 has broken collision for them, as well. I don't like how quickly this issue has been dismissed.

avatar image TJ V ♦♦ STAFF Aug 03 '16 at 07:55 PM

Hey Matt,

What version of the editor did you upgrade your project from?

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