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4.8.0 Preview 2 Physics more explodey?

Anyone else noticing more random reactions to contact in 4.8.0?

I have some gameplay based on stacking objects. There are rectangular objects with a variety of dimensions with an axis lock to have them stuck on the Y axis but free to move and rotate otherwise.

Gameplay consists of dropping blocks onto the existing stacks. Falling blocks have some impulses applied to influence fall speed and horizontal placement.

Moving to 4.8.0 I'm noticing that the stacks of objects that from have a tendency to explode when new objects land on them.


Product Version: UE 4.8 Preview
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asked May 18 '15 at 07:26 PM in Using UE4

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avatar image theonecalledtom May 18 '15 at 07:51 PM

Starting to narrow down when it happens. Seems more likely when I have my friction levels high. A dropping block comes down on one side of a bunch of touching blocks and the whole bunch goes kabamn and rotates up around the block that just hit them (kinda like a see saw). With lower friction levels I'm still seeing it but significantly reduced.

It seems to happen without control impulses applied.

Difficult to describe and my simple stacking brick test level doesn't exhibit the same problem.

avatar image theonecalledtom May 23 '15 at 09:14 PM

This continues to be true in preview 3. Mostly solid but occasionally landing a brick on the edge of a pile of bricks (anywhere between 3 and 30) causes the whole pile to blast off. Energy Conservation 0, cool piles of bricks exploding 1.

avatar image theonecalledtom Jun 24 '15 at 03:56 PM

I was able to reduce the explosion issues, though they still exist, by clamping angular velocity and adding more damping. This leaves the physics more dead, but my gameplay viable.

In my case if this is still a problem when I get to ship I can further reduce the bad effects with more hacks, however the physical effect will be much reduced and just not as cool (tm) as it was back in the good old days of 4.7 :)

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2 answers: sort voted first

Things seemed much better in 4.8.4 but I never closed this issue.


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answered Jul 30 '15 at 10:27 PM

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I also have severe problems with projects that have physics in them and can confirm problems here.


Could Epic please look into physics of UE4.8 as this renders many projects that were worked on since 4.6 unplayable.

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answered Jun 15 '15 at 06:52 PM

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