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per-poly collision problem !!

Hello guys,

I am trying to add Per-Poly physics collision between multiple meshes (By activating the option "Use complex collision as simple"), but the problem is that when I run the app, all the meshes are just standing in their places without any physical collision or interaction between the models. what is the wrong thing I am doing here ?

please see these images I hope they can help:

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Product Version: UE 4.20
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asked Aug 09 '18 at 07:48 AM in Bug Reports

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avatar image Jeff A ♦♦ STAFF Aug 10 '18 at 01:41 PM


We've recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.



avatar image MoutazH Aug 12 '18 at 01:04 PM

Thanks Jeff for your helpful comment, I have already reported the problem as a bug using the link you provided, still waiting for a reply about it though.. I wonder if there is someone you know that might be able to help me solve this problem ? thanks again :)

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1 answer: sort voted first

You can't have movable mesh if you use the Complex as simple collision. You'll have to add simple physics collision for movable objects

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answered Aug 12 '18 at 01:08 PM

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Eelis Otsamo
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avatar image MoutazH Aug 12 '18 at 01:14 PM

Thanks Steak for the answer, but I need to add a "per-poly collision" to a movable mesh..I can't use simple mesh collision for this project as it is a simulation project and i need the collision to be as precise as possible !!... do you have any idea about how can I achieve this collision accuracy for a movable mesh ?? Thank again :)

avatar image Eelis Otsamo Aug 12 '18 at 01:50 PM

Which 3d software you used to create the mesh?

avatar image Eelis Otsamo Aug 12 '18 at 01:58 PM

One solution is to open the static mesh in editor and use the automatic collision generation alt text Change settings anyway you want and then apply. Check the Simple Collision checkbox alt text Then you'll see the collision in green wireframe in the viewport alt text

avatar image MoutazH Aug 13 '18 at 06:57 AM

Yeah I know this method, but it doesn't give me the result i'm aiming for... it not as accurate as i want it to be... I am using Autodesk Maya and Cinema4D by the way.

avatar image Eelis Otsamo Aug 15 '18 at 10:36 AM

You can recreate the surface as accurate as it is in the per-poly collision, you just have to do it with multiple hulls. There is no way around it and this is not a bug. UE4 cannot use per poly collision for movable objects. You'll have to create the hulls, or change software

avatar image Eelis Otsamo Aug 15 '18 at 10:44 AM

Also, you don't have to use UE4 for the collision creation. You can do it in the 3d software by creating the hulls in there and naming them UCX_{Object name}_{index}. If your object was named Chair then the collision hulls would be UCX_Chair_00, UCX_Chair_01 etc. That way you will have fine control over the collision. Then just export them to fbx and when importing in UE4, check OFF the "One Convex Hull Per UCX" and it should import all the collision

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