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Why is my UCX collision being simplified

I'm trying to make a physics constraint motorcycle, I need to use a very high poly UCX collider for the tires to work properly. When I import the tires and collision it appears to be simplified: alt text (I boosted the subdivision when the bike drove way to bouncy before checking if it imported correctly, I know this is probably an unnecessary amount) I have tried the "One convex hull pull UCX" option both on and off, with similar results, the mesh shouldn't be concave anywhere, I even used Blender's "Convex hull" operator to make sure its convex. Importing the mesh into another program shows the full mesh. Importing it into Unreal without exporting the collision will auto generate an extruded octagon for collision, so I'm sure I'm getting the custom collision somewhat correctly.

Any guess as to what I'm missing? Also, do you happen to know if triangulating a collision mesh decrease performance, or is like a render mesh where it will always get triangulated?

Product Version: UE 4.15
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asked Jul 09 '17 at 03:03 AM in Using UE4

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csmith124
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2 answers: sort voted first

looks like this collision is more tesselated than original wheel mesh. its insane. in this case you can use per poly collision of original mesh ))

better use simpler cylinder mesh, maybe with edge bevel.

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answered Jul 09 '17 at 05:10 AM

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redbox
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avatar image csmith124 Jul 09 '17 at 06:10 AM

It's definitely more than was needed, but the limit seems to be too low to get it to work quite how I want it.It does need to be higher poly than the render tire though around the circumference, maybe a little lower than the render tire on the width. The rest of the collision in the game is pretty simple, so I think I can afford it performance wise.

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It's the same issue with the RollingBall template where you just bump up if you are 2 fast. I also tried a high tesselated mesh, but it seems it's restricted in some way. I got the feeling there is a reason for that. I could fix the bumping with a simple type and just using more angular drag or writing my own checks to slow down the rotation, but not the linear movement. Another solution is changing the way how you move. In the RollingBall example you can just use Impulse instead of torque. Would be great to hear if this workaround works or why it doesn't! <3

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answered Jul 09 '17 at 04:16 AM

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Ninjin
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avatar image csmith124 Jul 09 '17 at 05:54 AM

So it is limited. I've simplified the collision mesh a lot and works almost okay. Using a simple sphere collider doesn't work well when the bike leans into a turn. Adding force/impulse could work, but it seems like it would be difficult to do well. I'll see if I can work with this limit.

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