# How to control the number of seeds when using the Particle Tracer filter?
**URL:** https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238
**Category:** ParaView Support
**Created:** [October 10, 2025, 9:43am UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238 "2025-10-10T09:43:31Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@enrisang](https://discourse.paraview.org/u/enrisang)
#### Post date: [October 10, 2025, 9:43am UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238/1 "2025-10-10T09:43:31Z")
Hello,
I am using the Particle Tracer filter to simulate the injection of particles into a fluid domain via a catheter. Specifically, I have set the velocity field as the input and the catheter tip as the seed source.
I noticed that the number of particles injected matched the number of nodes on the surface (617 nodes = 617 particles, left view). Since I would like to inject more particles, I remeshed the surface to increase the number of nodes to 1019. However, only 769 particles were actually injected: it appears that not all of the nodes are being used as seeds (right view).
Why is that? Is there a maximum number of seeds? Are the nodes too close together?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [October 10, 2025, 11:44am UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238/2 "2025-10-10T11:44:46Z")
There is a “MaskPoints” property in the ParticleTracer, make sure to set it to 1.
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### Author:  [@enrisang](https://discourse.paraview.org/u/enrisang)
#### Post date: [October 10, 2025, 12:13pm UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238/3 "2025-10-10T12:13:39Z")
I can’t find the ”MaskPoints“ property in the ParticleTracer, but only in the TemporalParticlesToPathlines.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [October 10, 2025, 12:15pm UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238/4 "2025-10-10T12:15:43Z")
Ha right!
Please share your data then.
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### Author:  [@enrisang](https://discourse.paraview.org/u/enrisang)
#### Post date: [October 10, 2025, 12:44pm UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238/5 "2025-10-10T12:44:10Z")
Thanks! Here is the link to the shared folder with my data.
> **[particle-tracer-injection - Google Drive](https://drive.google.com/drive/folders/1g6i7eLlz6V-mjfkln1tqp6Rl95bv2Hb0?usp=sharing)**
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [October 13, 2025, 7:18am UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238/6 "2025-10-13T07:18:43Z")
Your points are right on the edges of the volume mesh, which makes some of them “outside” of the mesh because of floating point precision issue. A very small transfortm fixes that:
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### Author:  [@enrisang](https://discourse.paraview.org/u/enrisang)
#### Post date: [October 13, 2025, 9:44am UTC](https://discourse.paraview.org/t/how-to-control-the-number-of-seeds-when-using-the-particle-tracer-filter/17238/7 "2025-10-13T09:44:39Z")
Thanks! I slightly translated the surface along its normal and it worked. Really appreciate your help!