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PhysX Lab to UE4 collision problems.

Hello! I am trying to create a destructible asset using PhysX lab and using it in UE4. However after I export as .apb and import the mesh, when I play and shoot the mesh, it explodes randomly. This is not the issue however, the issue is that the collision of each chunk is not perfect, UE4 has sort of made a box around each chunk and not any details. This is why I think the chunks are standing on its sides and having weird physics. Note I am using the FPS example on a new level. I used a fracture map to fracture my texture in PhysX Lab. I am using UE4 4.2, im not sure if updating to 4.3 will help but it might, let me know! Im also not sure if it is part of my settings that is ruining this, or it is a bug. I have tried turning up the global gravity but the chunks just drop when shot, all at once and it doesnt fix the collision either. Also note,I have tried most methods found on the answer hub to resolve this, nothing worked (changed impactdepth, various blueprints, etc.). I also have noticed that when i select a chunk in the destructible editor (preview depth 1) it is a box around it, not conformed around the chunk, the blue outline that is. I hope this get resolved soon, thanks in advance!

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asked Jul 17 '14 at 12:03 PM in Everything Else

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avatar image Torabi Jul 17 '14 at 12:15 PM

I'm having the same collision problem. The chunks have collision boxes that are too large. So they end up floating above the ground.

avatar image Ben Halliday STAFF Jul 17 '14 at 10:47 PM


The blue box that surrounds your chunk in the Destructible editor is not its collision. I'm not sure why you have chunks sitting oddly. Would you mind linking me to a test asset with which this happens so I can see if there's a bug? Thanks!

avatar image AemonBarz Jul 18 '14 at 02:54 AM

Yeah I can send you the object when I get home, it is in an .apb file format. Thanks

avatar image AemonBarz Jul 18 '14 at 02:55 AM

Also, it happens with all the assets that I transfer from PhysX Lab so ill just send you any one. Not sure why this is though!

avatar image AemonBarz Jul 18 '14 at 06:55 AM

The following link is for anyone who wants to see what i'm talking about, just load the FPS game and put this in your scene and shoot it! https://www.mediafire.com/?6bzq4667nghzyll

avatar image Ben Halliday STAFF Jul 18 '14 at 06:56 PM

Thanks for the test asset. I'm seeing the same thing when I import it into my project, but creating a new destructible asset in PhysX Lab does not reproduce this behavior. I'm inclined to believe there's a setting in your PhysX project that is exporting the .apb with some unusual values. Would you mind creating a project that creates destructibles with this behavior and then putting that up somewhere for me? Thanks!

avatar image AemonBarz Jul 19 '14 at 01:25 AM

For some reason when i save the project and open it again, it opens with nothing in it. I'll just take screen shots of all the settings and post them up

avatar image AemonBarz Jul 19 '14 at 01:33 AM

Ok i have the pre fracture settings, the post fracture will be up soon! http://imgur.com/a/RpkN8#0 Oh and theyre not in order! Sorry!

avatar image AemonBarz Jul 19 '14 at 01:34 AM

Actually there is no need for post fracture, i didnt change any settings, but let me know if you need it!

avatar image AemonBarz Jul 19 '14 at 01:40 AM

Also, i'm using the fracture map included with physx lab with a simple box mad in maya exported as obj

avatar image AemonBarz Jul 19 '14 at 03:33 PM

I may have fixed the collision issue however, three more have arisen. But I think I fixed the collision by making the collision shape, collision decomposition in PhysX lab. And that fixed the issue where they would float and have random defying physics properties. But now I have an issue where the DM spawns about a foot off the ground no matter how deep I place it in the scene (I am trying to make it flat on the ground). And also when the destructible mesh is shot, all the chunks explode only on the Y and Z axis, and when all chunks land, most of them are standing on their edges up on the Y axis. Which brings me to my next problem which is that every chunk is being destroyed instantly as the object is shot, even when I select world overlap and impact damage in PhysX lab (I also put defaultimpactdamage to 1 and it didnt fix it). I'm pretty sure the collision is fixed because when I walk over the chunk it gets pushed and falls flat on the ground and can be pushed even more (however not all of them are interactable with?). They also collide with each other properly. I think the collision shapes get clipped through each other when the DM is destroyed, cause when I walk over them, their collisions are fixed (the chunks that are interactale anyway)! There is also quite a bit of lag when the DM is shot (probably cause so many chunks are being generated) so thats why I want impact damage, world support and support chunks! So if you can find a fix for this, it would be great! Heres a couple of screenshots! http://imgur.com/a/iqvMg#0

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I've tried creating a new DM with the settings you have displayed and it is not behaving the way yours does. There are a couple of possibilities here: most likely, either your mesh itself is being exported from Maya incorrectly or you have some mixture of settings in PhysX Lab that I'm not seeing that is causing this. I've messed around in PhysX for a while and wasn't able to come up with anything that would do this, so my guess is that it has something to do with your export process from Maya.

The asset you attached earlier needed to be scaled up significantly for me to test it properly, and scaling it caused some very unusual behavior. I'm wondering if this happens for you as well? If you create your mesh using centimeters as the base unit in Maya, and export it as an FBX, do the same problems occur?

Otherwise I'm not certain what could be causing this. If you'd like, you can send me a test mesh and I can attempt the same process in PhysX Lab so we can maybe narrow it down to that as the root of the problem. If you do, please send it exactly the way you have when you import it into PhysX. Thanks!

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answered Jul 21 '14 at 08:09 PM

avatar image AemonBarz Jul 22 '14 at 12:01 AM

Ok so I scaled it out directly from maya then exported to PhysX Lab and fractured it using the same settings. I imported it to UE4 and it seems to be working in the FPS template, however some pieces dont break no matter how much damage I apply with the gun or the damage threshold is significantly higher than the rest of the chunks. The collision is fixed and the seems to fall normally. I tried to shoot it in the FPS game and the mesh just disappeared, I only had time to try once before I had to go, but i'll try again tonight. Thanks for all the help, one last issue before this dilemma is resolved.

avatar image AemonBarz Jul 22 '14 at 12:24 PM

Yeah so the DM for some reason just disappears when I shoot it in the FPS sample, i'm not sure if it is just flying away REALLY fast or it just straight up disappearing. However scaling it up fixed almost everything in the FPS template, the only problem is that it can take damage on the first hit, and explodes normally, then after I try to shoot the remaining chunks, after a few shots the second chunk breaks then no more. No matter how much I spam, after the second chunk breaks off, no more can be broken off. I have also found that if I break the chunks in a specific order that can work sometimes, but not always. Thanks so much again and I hope you can resolve this asap!

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