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Physics objects sometimes stick to each other

Hey everybody. I am working on a stacking game in "2D Side Scroller" Mode and I spawn boxes at my anchor point. Now my problem with the boxes is, that they sometimes start sticking to each other which is not great for a stacking game. The boxes are from the parent class Actor and have a collision box generated by the engine when importing the paper 2d sprites. I hope somebody can point me into the right direction to let them behave like normal objects that collide and stack but do not stick.


If you need more infos / screenshots of objects let me know.

Thanks in advance for your time, very appreciated

Product Version: UE 4.17
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asked Sep 04 '17 at 04:02 PM in Using UE4

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avatar image sharp3ned Aug 05 '19 at 05:13 PM

I'm having this exact issue. Making a 2D tower stacking game. The only solution I've found is to make the dropped pieces go slower, either with gravity or their maximum linear velocity. I am still searching for a solution to make them drop quick and have correct physics.

The problem seems to be the event tick not catching the moment of impact correctly, delaying the physics reaction? I constrained the location and rotation of pieces so they only interact in 2D space. I'm working with the physical material to see if I can get any reasonable results. I've tried replacing the dropped actor with a replacement actor on-hit, but this really only complicates the issue. It seems like my pieces with more complex collision (shrink-wrapped) have slightly better interaction, but still occasionally 'stick'

I'll update if I find any usable solutions, open to trying any suggestions!

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I'm 99% sure I found the solution. I know this is an old post, but I thought I would answer in case anyone like me still had this issue.

In the actor's details panel, locate the 'collision' section, and check the 'use ccd' box. Like I was saying before, I think it's lag in the game's tick causing the sticking to happen, 'continuous collision detection' must be more reliable for this type of 2D interaction. I upped the gravity x10 with this solution in place and still didn't have any blocks sticking, where before this would cause every block to stick.

My only worry is this making a measurable impact on the game's performance, if there are many of these dropped actors present at once.

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answered Aug 05 '19 at 05:55 PM

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avatar image TheCell Aug 05 '19 at 08:23 PM

even though this is an old question I think to have this solved is still relevant. Great job :)

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