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Vehicle wheel collision problem


We have a problem with the vehicle system. We have checked all tutorials, videos and other relevant stuff that posted by either community or epic heroes, but couldn't find a point about that.

We have imported our vehicle model to Unreal Engine 4, set all necessary settings with that. Model has 4 tire bones which are connected to root bone placed at 0,0,0, defined collisions as sphere for wheels, box for body temporarily. When we press forward button, force goes to wheels, not problem with that either.

But the weird point is, when we set wheel collisions in physics asset as "kinematic", (body(root) stays at default), unreal does not recognize wheels' collisions. Vehicle falls to ground within collision of the body's constrains.

If we set all wheels as simulated, problems'd have been solved, but as predicted, vehicle does not move in that case. If we set wheels as kinematic, wheels go under the floor, unreal detects only body collision.

By the way, if we simulate the vehicle's physics in physics asset tool, physics go crazy, but in level scene as controller, that physics madness is not happening.

Thanks for your help in advance.



Running the game: (Result) alt text

Physics asset - root selected: alt text

Physics asset 2 - tires selected: alt text

Blueprint 1: alt text

Blueprint 2:alt text

Simulating on physics asset tool: link text alt text

Product Version: Not Selected
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asked Sep 24 '14 at 09:37 PM in Using UE4

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avatar image Jacky Sep 24 '14 at 10:01 PM

Which version of the engine are you using? It isn't necessary to set the wheels to Kinematic since 4.4 as far as i know. Leave them at Default and see how it goes.

avatar image burak.io Sep 25 '14 at 06:57 AM

We're using 4.4.0 currently. But even though we set wheels as default, it inherits root's characteristic as default or simulated, in short;

root = default, wheels = default => No Collision on wheels

root = simulated, wheels = default => Collision exist, but no force on wheels

root = any, wheels = kinematic => No Collision on wheels

root = simulated, wheels = simulated => Collision exist, but no force on wheels

avatar image burak.io Sep 26 '14 at 12:11 PM

Updated engine to 4.4.3, still no effect. Any ideas?

avatar image [Epic]Ori Cohen STAFF Sep 26 '14 at 03:55 PM

can you try the command pxvis collision. This should show you a debug drawing of the actual wheel simulation. Jacky is right, you should be able to leave the wheels to default. Is it possible your wheel class has problems? Is the wheel radius set correctly?

avatar image burak.io Sep 28 '14 at 10:16 AM

Hello Ori, thanks for your reply, I have attached pxvis collision and show collision debug results.

alt text

That's quite weird actually, we couldn't find out why pxvis collision seems rotated. Do you know how we can fix this?

avatar image burak.io Sep 29 '14 at 06:35 AM

Also there's a video about the situation. link text

avatar image Pierdek Sep 29 '14 at 08:22 AM

Export car fbx from Vehicle Sample and look how wheels' cordinate system is constructed. In the skeleton viewport should be: X - point forward Y- Right Z - Up

avatar image [Epic]Ori Cohen STAFF Sep 30 '14 at 11:25 AM

I suspect this is the issue, can you confirm BurakShamansoft?

avatar image Jacky Sep 30 '14 at 01:16 PM

Also, once you set the position of the parts as Pierdek described use an Xform modifier(if you are using Max) before you link the wheels to the body.

avatar image burak.io Sep 30 '14 at 02:08 PM

Thanks for your replies at first. Pierdek, if you have mentioned about joint rotation of wheels, we tried both positions and nothing has changed. Jacky we're using maya as third party 3d soft, not max. It seems weird actually, as you know x-y-z coordinates of maya and unreal are quite different. At the beginning, we suffered export-import issues which are caused by axis difference, but designing in maya axis, exporting to unreal with "Select up-axis as z" option selected solved the problem. We applied the same solution to wheels also, but it didn't seem okay. Also tried the change wheels axis to other options, nevertheless that has not solved it.

You can download the fbx file that we used on this link.


avatar image Jacky Sep 30 '14 at 02:39 PM

Ok, i got it working properly in Phat, but i passed it through Max > got rid of the bones and skin modifiers > reset Xform > and linked the wheel meshes to body mesh. I'll let you know if it works as a vehicle BP too.

avatar image Jacky Sep 30 '14 at 02:47 PM

And it works perfectly. :) Would you like me to send you the whole vehicle BP or do you want to solve this issue with Maya yourself?

avatar image burak.io Sep 30 '14 at 04:40 PM

I'd be grateful Jacky :) But all of our designers are using maya and blender, if it is an issue that caused due to maya exporting system, it'd be painful for us in future. It's weird to get such problem in maya, it's a widely used program after all.

avatar image Jacky Sep 30 '14 at 04:54 PM

It cant be Maya related since many people including Epic artists are using Maya. It is something you are missing in your workflow but i dont know what since i have no Maya experience. Ask around in the forums if you cant get further help here.

Here's the file: https://www.dropbox.com/s/i5n7mfpxfn3zc0e/Fiat.rar?dl=0

Unzip > Copy the Meshes folder in Content folder > Paste it into your project's content folder and everything should work as expected. The only extra you need to do is set wheel radius in wheel blueprints.

avatar image burak.io Oct 01 '14 at 06:40 AM

It works perfectly as you said Jacky, thanks, by the way, did you see any anormality in our model before you modify it on Max? I mean in joints, bone connections etc. Because we set all adjustments as you did in the file, but ours are still not working.

avatar image burak.io Oct 01 '14 at 08:29 AM

By the way can you send the fbx model that you modified and exported to unreal?

avatar image Rubenchu89 Aug 01 '16 at 11:51 PM

Hi, I have this exact same issue but I have to use Maya. All help is welcomed.

avatar image Shepp Apr 26 '17 at 03:49 PM

hey guys i have a similar probleme on my car but i can't fix it :c alt text this result in unreal : alt text

so i don't know what to do :/

ps : sorry for the bump

maya_preview.png (110.2 kB)
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6 answers: sort voted first

I fixed it in C4D by rotating and rebinding he joints, if anyone wants that FBX, here it is...


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answered Nov 01 '14 at 05:37 AM

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avatar image burak.io Nov 01 '14 at 12:08 PM

Anadin you are an angel, thank you :)

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If you guys allow me to post something to make it clear and simple?

i had tons of problems too, i spent many hours on this, and i have many copies of the same car just because of all this

finaly i found out that it is far simpler than i thought, I used the mannequin for measures.

  • All geometry like said, xform before rigging

  • Car_Front pointing to the right

  • All bones pointing to the right

  • make rigging in one chunk (UDK does not seem to like multi parts in skeletal any longer)

  • then do the skin modifier to geometry when exporting this it simply worked right of the dock without any prob.

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answered Jul 20 '15 at 11:59 PM

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avatar image burak.io Jul 23 '15 at 10:35 AM

Thanks buddy, that would be useful for devs that face with this issue.

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Okay, Jacky's method has solved the issue, even in maya. As I understand, 3ds Max's reset xform equals to Maya's Reset transformations. After setting all bones properly, we reset transformations and that made the problem been resolved. Thank you Jacky! :)

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answered Oct 01 '14 at 11:10 AM

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avatar image Jacky Oct 01 '14 at 02:28 PM

Glad you figured it out in Maya too! :) Also keep in mind that you dont need to use bones if there is an equivalent of Link in Maya too. Just set the pivot of the body at 0,0,0, set the wheels' pivots accordingly and then link the wheels to the body and export. Then select Import Rigid Mesh in import dialog window.

avatar image burak.io Oct 20 '14 at 05:18 PM

Jacky, hello again, do you still have the fbx file that you edited and exported to Unreal? We still have that kind of problems, if you can send, our designer will analyse it. We gonna have bats in the belfry :) We are still crawling with similar issues.

avatar image Jacky Oct 20 '14 at 05:27 PM

Sure. It's still in my dropbox so the link still works. Here: https://www.dropbox.com/s/i5n7mfpxfn3zc0e/Fiat.rar?dl=0

Edit: Wait...you want the FBX file and i dont have it anymore unfortunately. :\

avatar image burak.io Oct 20 '14 at 06:20 PM

Hmm, I know probably it'd be tiresome for you but really it became a keypoint for us :\ If you can remake it with most basic, less exhaustive way for you, I'd be appreciated Jacky. Weird thing is that, when we get some working model from somewhere, import it to Maya and re-export it to Unreal without changes, still could not get a proper working vehicle.

avatar image burak.io Oct 20 '14 at 06:30 PM

Or could you tell how were your export settings when you exported to Unreal, because shortly before we tried to import a previously working vehicle model to Maya, without any changes export it to fbx and unreal, no collision on wheels. Its really strange. We'll go crazy about that :P

avatar image Jacky Oct 20 '14 at 06:44 PM

Here are my export settings:

alt text

Closed tabs are irrelevant to this issue so you can consider them at default settings.

I'll try to remake the FBX but i doubt that it will make a difference. In the meantime you can try to ask about this in the forums(forum is down right now for maintenance but it should be up in half an hour or so) so that Maya users with vehicle experience can help you out.

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answered Mar 17 '18 at 08:25 PM

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I need help please, I have the same problem but on blender and not on maya

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answered Jul 06 '18 at 04:35 PM

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Plz jacky can you reupload the link.

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answered Jul 28 '18 at 06:34 PM

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