Isosurface

[geotyr]

Hello,

I am working with a point set in x, y, z, sf.
I am trying to create an isosurface using the scalar field.
It is a standard option in 3D visualization of scientific data but the result is usually visual and cannot be exported as a mesh.

Is there any way to do that with Cloudcompare?

The isosurface is based on a threshold applied on the scalar field. I have tried to extract these points, compute normals and do a poisson reconstruction but the results do no respect the shape of the points set.

Thank you for your help.

[daniel]

Not sure to understand. Do you have a 'volume' point cloud? Can you show me what your cloud looks like once you have applied the SF threshold?

[geotyr]

Okay,

so I have been working on the subject. The isosurface is the equivalent of topographic contour lines for volumes.

My first problem was that the volume that I generated using the SF filer was full of points, so I applied another filter in order to generate the shell (see in attachment). The problem now is that shell has interruptions or holes and the creation of the equivalent surface i complicated using 3D software. So I contacted the support of the software I used to create the data and they told me that I could already export the isosurface from the program.

The format is an ASCII file with at each line the XYZ coordinates of the vertexes of each triangle of the isosurface. Is it a format I can open with cloudcompare? I tried to import it as stl but the coordinates of the points are negative. Shifting the coordinates to positive values is enough? Is there another format I could use?

Thank you

[daniel]

Do you have only the vertices in the file? Isn't there something else to describe the triangles? Could be an OFF file in this case.

Can you send me the file maybe?

[geotyr]

the file only contains the 9 coordinates of the vertices of the triangles of the mesh
there is no header or anything else
it is a raw format
the size of the compressed file is of around 5mb
How can I send it to you?

[daniel]

Should be small enough to send it via email: cloudcompare [at] danielgm.net

[geotyr]

OK

So this format cannot be loaded directly in CloudCompare.

Thanks for looking at the data.

I have been looking for other options of software that we could use for the export of the isosurface. One gives the option of a vtk format. It is a demo version and I cannot export data to try it. I am not familiar with vtk files. Would it be okay to have the isosurface in this format?

[daniel]

If you have volume data such as a CT scan, then you could use ITK Snap or Slicer.

And to answer your question: we do support the VTK format. It should work as long as the exported isosurface is composed of triangles.