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Enabling Physics Mesh constrains extranges behaviors BP

Hello, im making a character to do a ledge jump, when he jumps, during the move from the jumping point to the ledge location, i enable the physics so the character can do a boncing efect when reaching the ledge, but once i enable the physics, the character body jumps really crazy, and some bones separates way too much from joints for example the the foot stretches out of the leg, making it look like a gum. I dont know if it has to do with the bone acceleration, or something wrong in the Physyc Asset. But it is driving me crazy. I followed all the UE PhAT videos instructions. By the way... in UE4.4, in the PhAT editor, the yellow line in the constrain doesnt show anymore like in 4.3 and previous.

Any help would be appreciated!

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asked Sep 23 '14 at 09:29 PM in Using UE4

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Does the issue happen if you just drag the ragdoll into an empty level and hit play? This would help debug if it's an issue with the asset or with some kind of initial velocity.

In 4.4 the yellow line has been replaced with 3 lines (red green blue). Each line has its range of motion visualized with a fan with the same color. We will need to update these videos though as it's definitely a new way of looking at it.

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answered Sep 23 '14 at 09:50 PM

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[Epic]Ori Cohen STAFF
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avatar image OFEKA Sep 23 '14 at 11:34 PM

Sorry, i made a mistake saying that its bouncing, i meant to say that the character is jumping a Swinging once he reaches the ledge.

I uploaded a video explaning the problem


Let me know what you think!

avatar image [Epic]Ori Cohen STAFF Sep 24 '14 at 02:20 PM

if you put the ragdoll into an empty level does it simulate correctly or do you still get issues?

avatar image OFEKA Sep 24 '14 at 02:55 PM

Im working on this projects in 2 different computers, one is way faster than the other. Well, the crazy jump of the bone was fixed setting the physic linear velocity to 0 one step before enabling physic (Set All Bodies below Simulate Physic). i noticed that the Gum behavior was only happening on the slow computer, i realised that due the low frame rate (around 20fps), then reading some PhAt articles i saw something called "Substepping" in the Physics Options of the project, i turned that on and the gum behavior is gone! After all i guess all was happening due the physics calculations and the low framerate! I hope that keeping this option enabled wont affect the whole gameplay.

avatar image [Epic]Ori Cohen STAFF Sep 26 '14 at 03:03 PM

It should be safe to use sub-stepping, it's actually designed for exactly this case.

avatar image OFEKA Sep 24 '14 at 11:22 PM

Hello Ori, i've been working more and more hours in the project and after testing several times i realise that some UE4 functionality starts to give wrong values or stops working properly when run below 20 fps or so. That happened before with the Physic simulation, and now i was working with VnterpTo and it never reach the value when running below 20 fps, when i say never i mean it gets stuck in a certain value, I usually work with blueprint window opened, when i close it, i gain more fps, when i run the project once again, it work properly. So far that happened to me with those 2 cases, probably more things would happen due the low fps, but i consider that 20 or 18 fps shouldnt be that to make things work wrong!

Hope this can give you any clue to trace this bug! thanks!

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