# Keyframing Force Reinjection Every N Steps on Particle Tracer disappearing particles

**URL:** https://discourse.paraview.org/t/keyframing-force-reinjection-every-n-steps-on-particle-tracer-disappearing-particles/15833
**Category:** ParaView Support
**Created:** [December 4, 2024, 8:03pm UTC](https://discourse.paraview.org/t/keyframing-force-reinjection-every-n-steps-on-particle-tracer-disappearing-particles/15833 "2024-12-04T20:03:50Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![mvanmoer](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mvanmoer/32/2623_2.png) [@mvanmoer](https://discourse.paraview.org/u/mvanmoer)
#### Post date: [December 4, 2024, 8:03pm UTC](https://discourse.paraview.org/t/keyframing-force-reinjection-every-n-steps-on-particle-tracer-disappearing-particles/15833/1 "2024-12-04T20:03:50Z")

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Hello,  
I am attempting to mimic an injection and wash cycle of particles in a volume. That is, particles are reinjected every timestep up to a point, reinjection stops, then existing particles continue to be advected. I have created a Particle Tracer and in the Time Manager added ForceReinjectionEveryNSteps. Attached is a screenshot of the pipeline and Animation Keyframes dialog.

 ![keyframing_reinjection_pipeline_setup](https://discourse.paraview.org/uploads/default/original/2X/4/4f9470729355ab30e464e1dfb30bdfb264df09fc.png)

For the first 6 timesteps new particles are injected. At this point there are ~6000 particles.

 ![keyframing_reinjection_up_to_keyframe](https://discourse.paraview.org/uploads/default/original/2X/f/f6acf3712a1fc22137dd289ef84317ead4af7ba9.png)

On the 7th timestep, the particles stop reinjecting as expected, but the majority of them disappear, which is unexpected and not what I need.

 ![keyframing_reinjection_at_keyframe-missing_particles](https://discourse.paraview.org/uploads/default/original/2X/9/907569a1d7d9ae41b057c95a7a0d8118fa7c02fe.png)

Any thoughts on what is happening here?

Thanks,  
Mark

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### Author: ![mwestphal](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mwestphal/32/17_2.png) [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [December 5, 2024, 4:01pm UTC](https://discourse.paraview.org/t/keyframing-force-reinjection-every-n-steps-on-particle-tracer-disappearing-particles/15833/2 "2024-12-05T16:01:24Z")

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Hi @mvanmoer

Please share your data and ideally a state file.

Best,

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### Author: ![mvanmoer](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mvanmoer/32/2623_2.png) [@mvanmoer](https://discourse.paraview.org/u/mvanmoer)
#### Post date: [December 5, 2024, 4:21pm UTC](https://discourse.paraview.org/t/keyframing-force-reinjection-every-n-steps-on-particle-tracer-disappearing-particles/15833/3 "2024-12-05T16:21:41Z")

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Hi Mathieu,

[https://uofi.box.com/s/66g47xuczkqzcdjrc5dsau8ahxbepj0z](https://uofi.box.com/s/66g47xuczkqzcdjrc5dsau8ahxbepj0z)

Thanks! edit - I’m using ParaView 5.12.0

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<div class="post-metadata">

### Author: ![mvanmoer](https://discourse.paraview.org/user_avatar/discourse.paraview.org/mvanmoer/32/2623_2.png) [@mvanmoer](https://discourse.paraview.org/u/mvanmoer)
#### Post date: [December 10, 2024, 3:58pm UTC](https://discourse.paraview.org/t/keyframing-force-reinjection-every-n-steps-on-particle-tracer-disappearing-particles/15833/4 "2024-12-10T15:58:22Z")

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I have a partial workaround:

1. Separate just the injection cycle timesteps
2. Create the same pipeline as above and Save Data (or Save Geometry)
3. Use the .vtp of the last injection timestep as a seed source for the wash cycle

This shows the advection that I was aiming for, but there doesn’t seem to be a way to take the ParticleAge from the injection and use that as an offset during the wash.