# stream tracer from point with ray
**URL:** https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481
**Category:** ParaView Support
**Created:** [March 15, 2019, 3:32pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481 "2019-03-15T15:32:29Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@drudox00](https://discourse.paraview.org/u/drudox00)
#### Post date: [March 15, 2019, 3:32pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/1 "2019-03-15T15:32:29Z")
Hi all !
I would know if there is a way to create a stream tracer from custom filter using a set of data (in my case 5 polydata vtk point representing polymer) and use a certain ray around it … there is such possibility ?
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [March 15, 2019, 3:57pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/2 "2019-03-15T15:57:24Z")
Do you mean the `Stream Tracer With Custom Source` filter?
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### Author:  [@drudox00](https://discourse.paraview.org/u/drudox00)
#### Post date: [March 15, 2019, 3:59pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/3 "2019-03-15T15:59:51Z")
yes!!
I try to use the full box and the polymer as source ! I obtain 5 very close line (that looks one) what I need is to having an area around the polydata to use as source … or using the filter properly setting a ray around the source … I don’t know
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### Author:  [@drudox00](https://discourse.paraview.org/u/drudox00)
#### Post date: [March 15, 2019, 4:39pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/4 "2019-03-15T16:39:03Z")
Do you have any advice ?
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [March 15, 2019, 4:59pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/5 "2019-03-15T16:59:10Z")
I really don’t understand what you are asking. With the `Stream Tracer With Custom Source`, just set the volume with the vector field as the `Input` and some other data set as the `Seed Source`. The filter will trace streamlines from every point in the `Seed Source`.
I am guessing that you are asking how to place seed points. The only trick is to create a data set with points where you want to trace from for the `Seed Source`. You can use one of the sources provided by ParaView (such as `Sphere`, `Plane`, or `Box`) or a filter to modify an existing data set (such as `Slice`, an extract, or maybe `Transform`).
If the points in your `Seed Source` are too close, maybe you can try to first `Transform` them to scale the size up (scale greater than 1).
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### Author:  [@drudox00](https://discourse.paraview.org/u/drudox00)
#### Post date: [March 15, 2019, 5:04pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/6 "2019-03-15T17:04:42Z")
I’m maybe not well explain ! I’m able to use the filter properly ! but I want to increase the area around the polymer as source !
basically I guess your suggestion to create a sphere around the data is what I was looking for !
How can I create it around my polymer data ?
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [March 15, 2019, 5:08pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/7 "2019-03-15T17:08:23Z")
I can’t think of an automated way to do that. Your best bet is to look at the `Information` tab and create a sphere at the center of your polymer data and a radius as you wish. That said, if you are doing all that, you may want to just use the standard `Stream Tracer` and use its built in point source with the same center and radius.
Another approach might be, as I suggested earlier, to apply the `Transform` filter to your polymer data and scale it up to make it bigger.
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### Author:  [@drudox00](https://discourse.paraview.org/u/drudox00)
#### Post date: [March 15, 2019, 5:34pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/8 "2019-03-15T17:34:57Z")
But if I scale the polymer up, I still get just 5 line (one for each point) right ?
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [March 15, 2019, 5:55pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/9 "2019-03-15T17:55:41Z")
Yes, that is correct. Earlier you said that the 5 lines were so close that they looked like 1 line. I thought you wanted to see the 5 distinct lines. If you want more, then yes you will need to create new geometry with more points (with the sphere or point source).
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### Author:  [@drudox00](https://discourse.paraview.org/u/drudox00)
#### Post date: [March 15, 2019, 5:57pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/10 "2019-03-15T17:57:27Z")
ok !! thank you very much for your help ! I think now I have all the knowledge to proceed with my post processing !
have a nice week end
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### Author:  [@drudox00](https://discourse.paraview.org/u/drudox00)
#### Post date: [March 18, 2019, 5:13pm UTC](https://discourse.paraview.org/t/stream-tracer-from-point-with-ray/1481/11 "2019-03-18T17:13:12Z")
Dear Kenneth,
When you speak about `transform` filter may you explain me how to increase the size of the polymer (data) but respect to the same center ! basically I would like to increase but respect the same center of mass ! How can I do that ?