Define boundaries for Poisson reconstruction

[Aurel]

Hi, I'm quite new to CloudCompare but I'm really enjoying the use of it.
I've acquired a river bank cloud and I'd like to convert it into a surface.

The attachment bank-cloud.jpg is no longer available

The Poisson reconstruction seems to be an appropriate tool as it manages to reproduce well the complex topography of the area. However, when running it, it looks like the tool is trying to interpolate the summit points of the river bank with the foot points, thus generating a quite odd surface:

bank-cloud.jpg (205.04 KiB) Viewed 23511 times

Is there a way to define boundaries within which I want the program to run? It could also help me preventing interpolation where data is lacking on the "cliff" (where vegetation was present).

Thanks very much in advance

Aurélien

[daniel]

Are you speaking about the 'bubbles' that Poisson generates (in which case you have to play with the 'density' scalar field).

Otherwise, you can manually segment the cloud?

Or did I misunderstood something?

[Aurel]

Yes I'm speaking about this big "bubble" (cf image) having no real topographic significance:

bank-poisson.jpg (41.7 KiB) Viewed 23358 times

As much as possible, I'd like to avoid having to manually segment the cloud. Therefore, I'm looking for a way to prevent CC from constructing an interpolated surface between the top of the river bank (yellow-orange color on the image) and the foot of the bank (blue color).

I'm not sure what the 'density' scalar field refers to, but I'll give it a try.

Thanks

Aurélien

[daniel]

The density scalar field is output by Poisson. By 'construction' it always create a closed mesh (hence the bubbles). But it can also output the Poisson grid 'density' as a scalar field. The farther a part of the mesh is from the original cloud, the smaller density it will have. This way you can easily remove the parts of the mesh that are too far from the original mesh.

And you can do it very simply by interactively playing with the 'Density' scalar field display parameters (the 'minimum displayed' value = the left circle on the S.F. widget in the mesh properties) and eventually use the 'Edit > Scalar fields > Filter by value' tool to split/cut the mesh where you stopped.

[Aurel]

Thank you Daniel,

indeed, I did not tick the box "output density as scalar field" when running the Poisson reconstruction.
It works fine, and I've been able to delete most of the irrelevant surfaces.

Have a nice day,

Aurelien

[sololeakrg9]

As much as possible, I'd like to avoid having to manually segment the cloud. Therefore, I'm looking for a way to prevent CC from constructing an interpolated surface between the top of the river bank (yellow-orange color on the image) and the foot of the bank (blue color).

[daniel]

Well, that' how the PoissonRecon library works (by the way, this is a third party library, all credits and praises should go to its author, Misha Kazhdan ;). And I don't know if there are options to do that automatically...