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Skeletal mesh landing gear collision problem

We're trying to create a landing gear for an airplane. One way to do it to import landing gear as a static mesh with its own collision and animate with blueprints. We are trying to do it with Skeletal Mesh so that the landing gear is part of the plane but we are encountering a problem with collision. The landing gear animates nicely but the collision from physics asset does not follow the gear, and the plane looks like its still standing on the gears even after they are up. Looking for a theoretical input on how it should be set up to work properly with SKM.

Product Version: UE 4.20
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asked Dec 05 '18 at 10:52 AM in Blueprint Scripting

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avatar image Tuerer Dec 05 '18 at 12:18 PM

So the entire plane is a single mesh, the gear including? I didn't really check how collision is generated for skeletal meshes, but when you import a static mesh, the default collision will be a cube that encompasses the entire mesh, regardless the empty areas, so maybe with the skeletal mesh it is the same?

Maybe you can try and remove collision for the gear, add a collision capsule in the plane blueprint and attach it to one of the gear bones, so that the collision capsule would move along with the gear?

avatar image Spaehling Mar 25 '19 at 02:06 PM

Hey tuerer, thanks for the answer and sorry for the delay. yes thats exacttly what we did and this works ok so far. but still trying to fix it, so we can use phyiscs asset.

avatar image SirToxe Mar 25 '19 at 12:59 PM

I am having basically the exact same problem. Did you ever find a good solution to this?

avatar image Spaehling Mar 25 '19 at 01:57 PM

hey, iam the team mate of irakli.

more or less. we have a workaround that works for us, but not a real fix.

i still work on this and i think they we need use those nodes:

1 "set all bodies below simulate physics"

2 "set all bodies below physics blend weight"

So imagine we start with our Airplane on the Ground and we start to fly.

Gear Up: we need to simulate phyics on the wheels, when they are on the ground. Then you need to disable all animated parts by set blend weight to 0. (gear, wheels).

The rest parts of the plane (vehicle_base bone) i think should be manually turned blend weight 1 (#2) and turn on simulation (#1). but the rest needs to be simulated.

Then run the Gear Animation.

Gear Down: We play the Animation. After the animation ends and if the wheels are back to the ground, bring for wheels and gears back to 1 (#2) and turn on simulation on again (#1)

so iam not 100% sure yet, bit annoying and sketchy, but finally i think it could be worth it. if you have like more then 10 planes, its nice to have everything in one skm.

i wasn't able to work this out a 100% yet. but maybe it helps you to start with.

avatar image SirToxe Mar 25 '19 at 03:06 PM

Hey thanks for the reply. I will take a look at this tonight.

I have asked a related question earlier today: https://answers.unrealengine.com/questions/884961/view.html

Even though I talk about arms or ragdolls, this is actually about a plane and landing gear as well. What I was able to find out so far was that it has everything to do with simulated physics. If I enable physics then the colliders will stop working. As long as there are no physics involved everything works fine.

avatar image Spaehling Mar 27 '19 at 09:07 AM

interessting. Lets try to find out together. I will also take a look again. I tried it yesterday and failed fixing it. but i will try again.

avatar image SirToxe Mar 27 '19 at 03:39 PM

Heyo, just a quick update: I was able to find a working solution but I had to do a workaround. I created three sphere colliders (one for each wheel) and added a socket to each tire. When I raise or lower the wheels I update the position of every collider to its associated socket. This works but I would have prefered to just attach the colliders directly to the animated sockets and let the engine handle the position updates. Which in itself works though this removes the collision from the colliders.

I will probably post a video of this setup in a couple of days on this Answerhub to look for feedback. Just because I am curious if I can improve this. But so far I can live with this solution.

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