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Convex/Concave Collisions


I was wondering if it was possible to get any concave shapes to simulate collisions.

Let's get the example of a bowl of cereals and let's say I want to make a game in which one you have to fit the more cereals in the bowl (silly idea, I know, but it's a good example :P)

Is it possible to use any concave shapes ? If you try to bloc-out the bowl using the auto-generator, it will look pretty clean outside, but the inside will be way inaccurate and looking messy...

I've red more than once that UE4 was only supporting convex collisions. But what about a little bit more complex shapes that needs convex blocking out as well ? (Let's say a cereal falling into my bowl). Or even connecting male-connector into a female-connector like shapes ?



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asked Feb 17 '15 at 03:30 AM in Everything Else

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You can use complex collision by changing the collision complexity to UseComplexAsSimple. You can do this in the static mesh editor for the specific mesh you're talking about.

One limitation with this is that the complex collision cannot be physically simulated. This means that things like gravity and momentum will not be computed for the body. However, in the case of your cereal bowl this would still allow the cereal (presumably balls) to simulate and interact with the complex collision.

If you want both concave and full physical simulation you'll need to use multiple convex shapes. You can do this in the static mesh editor by using convex mesh decomposition.

Hope that helps

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answered Feb 17 '15 at 05:24 AM

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[Epic]Ori Cohen STAFF
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avatar image Hayaweh Feb 17 '15 at 10:06 AM

Hi, thanks for your answer, I was wondering if this was the only way.. It seems so. :)

Hm. About the physic. Would it work if my character would be holding it's bowl "in his hands" then ? Would the cornflakes get thrown away anyway ?

My problem was that currently, The collision mesh generated using convex mesh decomposition was not fitting the complex shape, Or at least not on the crucial edges/parts. So I think that the best will be to make the blockout manually in the 3D modeling tool.

Thanks for the infos.

avatar image [Epic]Ori Cohen STAFF Feb 19 '15 at 05:13 AM

If the character's movement is driven by animation then I believe this will work.

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