Particle Emission Cyclic Glitch when Parented #39528
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Reference: blender/blender#39528
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System Information
Mac OS; Macbook Air
Blender Version
Broken: (2.70
19e627c
) - CurrentShort description of error
In trying to create a light-streak type effect, I wanted to create a very tightly-controlled stream of particles.
Parenting the emitter to an Empty causes every 10th particle to be spawned in an incorrectly offset location.
Exact steps for others to reproduce the error
...Makes for an ideal zero-size emitter yet which also has normal data to work with (unlike an actual lone-vertex mesh)
I immediately noticed that it was a regular interval - every tenth particle - and so suspecting some kind of rounding glitch, I tried messing around with different particle amounts, lifetimes, cache steps and subframe values, but I couldn't get any joy no matter what I did.
I have omitted the cache to aid with small file size attachment, but this should be quite easy to reproduce on the receiving end, whoever reads this.
Just parent the Plane emitter to the Empty, bake, observe glitchy chain, then unparent and rebake, nice smooth chain.
(Both Compositing Nodes and Camera location are in fact set up to make it worthwhile actually pushing a render through to see the visual direction I was trying for)
Jarron-ParticleEmissionCyclicGlitchWhenParented.blend
Changed status to: 'Open'
Added subscriber: @Jarron
Oh I forgot to state the method of Parenting.
Neither works right I think, but they give different results.
Parenting directly via the Object tab is the one that gives the actual reported behavior of every nth particle having an issue.
Parenting via a Constraint "modifier" gives a kind of clumpy effect.
Might be related, might not be - but in either case it's not the effect I was hoping for.
Hmm maybe I should've titled this "periodic" glitch rather than "cyclic"
Added subscriber: @willi-2
I can repro the problem. Two comparing screenshots:
Without artifact:
With artifact:
That every 10th particle has an offset is because 10 particles per frame are emitted. I guess it has something to do with when the intermediate particles (the 9 between) are born and when their physics simulation starts. It seems one frame too late.
First I thought it's because of the faster movement of the emitter and you'd get the same glitch if you'd manually move the plane faster instead, but this could not be confirmed.
Added subscribers: @LukasTonne, @Sergey
@LukasTonne, can you have a look here? Might be a design limitation which would be nice to be taken into account for the new particle system you're working on.
Changed status from 'Open' to: 'Resolved'
Looks like this got fixed by
6416979b