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My Goal

...is to have a particle-trail-tail continue infinitely, despite having a "Frame Start / Frame End" property in the Particle System tab, rather than using keyframe animation.

My animation is a model of the solar system, where the planets are constrained to curves, and emit a particle trail which conforms to the same curve.

animation of the trails ending

My Setup So Far

  • The orbital paths are curves.
  • The planets are empties, using Object Constraint, targeted to the orbit-curves.
    • A UV sphere is parented to each empty as the planet object.
    • A plane is parented to the empty as the (trail) emitter object.
  • The orbit animations are keyframed on 1 and 360 as the curve offset percentage, and then set to linear extrapolation in the graph editor.
  • The particle trails have "Frame Start / End" properties, which are not animatable properties, rather than something that I know how to keyframe.

The Problem

The animation above is frames 264 - 456. The extrapolated curve motion continues past frame 360, but the frame-coded particle emitter does not.

I thought I would use linear extrapolation like I did for the orbits themselves, but I cannot seem to figure it out.

The Request

I'm looking for a way to make the trails continue indefinitely, regardless of how many frames the ending animation turns out to be.

Additional Potentially Useful Screenshots

My object organization and hierarchy:

My object organization and hierarchy

My particle emission settings:

My particle emission settings

My trail shrink is a texture blend, using a ColorRamp from white to black. The Influence is set to Size. The Mapping is set to Strand/Particle:

enter image description here

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2 Answers 2

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Array and Curve Modifier.

Going to offer up an alternative approach to using a particle system

enter image description here

Can make a similar set up using an array and curve modifier.

Slap together a Very quick example

  • Icosphere as planet

  • Add and empty, make the icosphere its parent. It will be used as an array offset object, ie its distance from ico will separate, its scale will cause each to be smaller.

  • Add an orbit.

  • Add an array modifier to the icosphere, with object offset targeting the empty

  • Add a curve modifier, targeting the orbit circle.

  • Have arbitrarily chosen the X axis to follow the curve

  • Ico Can be set to orbit infinitely by setting a driver on its X location based on the frame Continuous Looping animation - Differing rotational speeds

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    $\begingroup$ Hi @batFINGER, thanks for the reply. I find your method to be simple, elegant, and more clever than I was being with the particle system. -- I'd had my planet anchored to an empty, with the thought that later on I'll make the planet itself rotate around the empty. Do you know a way to use both rotation and trails with your method? Thanks again! $\endgroup$
    – Gabe S
    Oct 13, 2021 at 17:38
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    $\begingroup$ If just the planet is to rotate, not all the "followers" One quick method that comes to mind is a slightly larger planet with copy loc constraint to ico. $\endgroup$
    – batFINGER
    Oct 14, 2021 at 7:00
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You can do this with animation nodes, but...the first sphere is not the biggest one, i don't know if you can live with that...

here is the nodes setup:

enter image description here

result:

enter image description here

you can change the trail length by changing the fade length value

enter image description here

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    $\begingroup$ Hi @Chris, this is neat. I don't think it will work for my planet trails, but I'll definitely be studying this because I can see many future uses for it! $\endgroup$
    – Gabe S
    Oct 13, 2021 at 17:42

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