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Child hair particles set to "Interpolated" causes jittering when groom on alembic cache
Open, Confirmed, MediumPublic

Description

Blender 2.8x
Win10

Hi,
THE PROBLEM is that if you turn on "CHILD PARTICLES" and SET them TO "INTERPOLATED" MODE it causes JITTERING of them
acros surface of the geo from which roots.

When selecting "Simple" mode everything works fine - No jitter at all, perfectly sticked to the geo.

You can test it simply by switching from mode to mode to see this problem. Its already setuped for rendering using eevee but same problem using
Cycles renderer.

Note that I ve briefly tried to change export settings for Alembic during export of anim but nothing helped...still causes this problem.

Also note that when outputting alembic cache for animated object using transforms not armatures, it works ok. But when exporting alembic from armature animated
object this causes this problem.

please see this Zip archive with readme info and example scene....

Thank you,

Libor

Details

Type
Bug

Event Timeline

here is some rendered animation with close up of the hair particles jittering on my animated model (alembic cache)

pls when viewing change quality below video to highest resolution (1080p) or just download and playback at your desktop

Thx again.
L.

Philipp Oeser (lichtwerk) triaged this task as Confirmed, Medium priority.

Confirmed on first sight
(Looks like 2.79 has a similiar issue even)

@Sybren A. Stüvel (sybren): mind having a look?

@Libor Batek (lbatek) please put the description of the issue in this task, instead of hiding it in a ZIP file. Hiding it like this makes it invisible to the search engine, and makes it harder for developers to access as well.

@Sybren A. Stüvel (sybren) ok, sorry not doing it before....should be done right now

Have the same problem, here is a side by side basic test

Libor Batek (lbatek) added a comment.EditedApr 26 2019, 9:29 AM

I ve tested to render animation with mblur and hair on alembic cache and there is some problems too....not sure if it corelates to the above mentioned problems or its kind of new problem.

EXAMPLE_MOV (Apple ProRes)

still frame from animation with mblur...seems like hair particles doesnt refer to preceding frame position of the hair particles (not sure If I shouldnt use bake cache for particles??)

they spread from world origin