# How generate a set of interest points on a surface from some points.
**URL:** https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436
**Category:** Support
**Created:** [December 20, 2021, 10:18am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436 "2021-12-20T10:18:24Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@Miguel\_Socorro](https://discourse.vtk.org/u/Miguel_Socorro)
#### Post date: [December 20, 2021, 10:18am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/1 "2021-12-20T10:18:24Z")
Hello, I have been able to see in some surgical navigation systems (like Mako for example) selecting some points, the system can generate automatically a broader set of points in places of interest.
For example, in this case:
_Figure 1. A 3D image of the pelvis and three selected points._
Selecting those 3 points (A, B, C) is enough to generate these other set of points
_Figure 2. Points generated automatically._
Does anyone have any idea how to do these things, if there is any recommended methodology or algorithms? I suppose that in this case, it is possible adjust a circle to those 3 points and generate some points, but there would still be more points that cannot be generated from a circle.
Anyone have any ideas or recommendations on how to do these things?
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### Author:  [@lassoan](https://discourse.vtk.org/u/lassoan)
#### Post date: [December 20, 2021, 4:55pm UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/2 "2021-12-20T16:55:35Z")
Normally these surface points are acquired using a tracked stylus. Do you want to simulate this sampling?
You may consider posting this question (with some more details and clarifications) on the [Slicer forum](https://discourse.slicer.org) where hundreds of community members are using VTK for developing surgical planning and navigation systems (of course not completely from scratch but building on 3D Slicer).
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### Author:  [@Miguel\_Socorro](https://discourse.vtk.org/u/Miguel_Socorro)
#### Post date: [December 21, 2021, 1:54am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/3 "2021-12-21T01:54:59Z")
The 3 points (A, B, C) are selected in the 3D model of figure 1 and later the system is able to automatically generate the set of points shown in figure 2.
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### Author:  [@lassoan](https://discourse.vtk.org/u/lassoan)
#### Post date: [December 21, 2021, 4:46am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/4 "2021-12-21T04:46:23Z")
Does the system displays the points that the user touched with the stylus or the system just randomly chose points of the surface near the 3 initial points?
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### Author:  [@Miguel\_Socorro](https://discourse.vtk.org/u/Miguel_Socorro)
#### Post date: [December 21, 2021, 5:19am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/5 "2021-12-21T05:19:31Z")
@lassoan The system is capable of generating the points always with the same pattern from the same three initial points. The generating points are not random, you can see that they are displayed in specific areas and always the same amount in each area.
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### Author:  [@lassoan](https://discourse.vtk.org/u/lassoan)
#### Post date: [December 21, 2021, 5:32am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/6 "2021-12-21T05:32:32Z")
Sorry, it is still not clear for me why a surgical navigation system would generate this point pattern. Is it for patient registration? Which navigation system is this? How the patient registration is done?
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### Author:  [@Miguel\_Socorro](https://discourse.vtk.org/u/Miguel_Socorro)
#### Post date: [December 21, 2021, 8:49am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/7 "2021-12-21T08:49:23Z")
@lassoan It is the Mako system and it generates that pattern of points for a registration process, but it always generates the same pattern of points from the three initial points mentioned above.
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### Author:  [@Stephan\_Hahn](https://discourse.vtk.org/u/Stephan_Hahn)
#### Post date: [December 21, 2021, 1:00pm UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/8 "2021-12-21T13:00:44Z")
@Miguel_Socorro What means the color (blue, white) because, from the images, it seems that blue dots are further from the surface than white?
Is each point have a geometrical meaning (e.g. curvature) or is it a pattern? If it is a pattern, I will suppose that an [ICP](https://vtk.org/doc/nightly/html/classvtkIterativeClosestPointTransform.html) algorithm was used to align the pattern on the surface, using the 3 dots as initialization. It means also that you will need the template pattern to reproduce the result obtains by the software.
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### Author:  [@lassoan](https://discourse.vtk.org/u/lassoan)
#### Post date: [December 21, 2021, 5:36pm UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/9 "2021-12-21T17:36:02Z")
The question has been posted on the Slicer forum as well and I added some details about the registration process:
> **[How generate a set of interest points on a surface from some points.](https://discourse.slicer.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/21161/2?u=lassoan)**
>
> To give some more context, this is a point pattern that the Stryker/Mako surgical navigation system generates to guide the surgeon in surface point collection (page 33 in this online pdf): This is just a convenience feature to guide surgeons who...
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### Author:  [@Miguel\_Socorro](https://discourse.vtk.org/u/Miguel_Socorro)
#### Post date: [December 22, 2021, 2:03am UTC](https://discourse.vtk.org/t/how-generate-a-set-of-interest-points-on-a-surface-from-some-points/7436/10 "2021-12-22T02:03:24Z")
@Stephan_Hahn I really don’t know if the geometric meaning is related to a pattern or to certain curves. I think it must be a pattern, anyway I just needed to know what is the methodology used to work with these problems and your answer has helped me. Thank you.