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Anim Dynamics explode on first frame of render

Does anyone know why Dynamic Animations (like ponytails) would explode like crazy in the first two frames of a render but then function normally after? At first I thought it might be collision related, but I went ahead and deleted all the collision spheres and the problem still happens. It only seems to happen when rendering, not in Physics or Blueprint previews or in-game. Here’s a small video of the issue I am having:

Has to be a result of the PHAT asset settings.
OR - something caused by CHAOS maybe.
either way, without collision within the phat asset, the hair wouldn’t bobble the way it’s bobbling in the video… so what collisions did you delete?
To test the PHAT try disabling gravity and toggling the chain to see if anything reacts oddly or spazzes out - preferably after loading the same pose as the video, or you may never find the problem.

Also, as almost always, it’s not the only thing in the scene that isn’t initialized.
The fire, the candle, and any other physically based thing is probably delayed.
Generally, I start recording only after the scene has “spun up”.

  • I deleted the collision between every single capsule and sphere just to be sure. It still spazzes out and explodes on the first frame.

  • I tried disabling gravity on the hair, it definitely still spazzes out on the first frame, just doesn’t fall towards the ground afterwards as expected.

  • I generally have 10 frame handles at the start and end of my sequences, just in this case the effects of the explosive hair are lasting almost 100 frames before it settles down and behaves normally again. I suppose worst case scenario I can give the sequence 100 frames for the hair to calm down and just cut that out in post.

The thing that is strange is the hair was working fine yesterday. I have a suspicion the new version of Unreal (4.26.2) is in some way related to this problem since I finally updated to it last night and the problem started when I fired up the project today.

Depends on what version you came from, but it is possible, if not very likely.

So the phat asset is not doing this at all when you start simulating without gravity?

No, it still explodes on the first frame even with gravity disabled.

When looking at the phat asset in Persona directly?
If thats the case the issue has to be one of the collisions - or bone orientation constraints.