CloudCompare forum

Hi everyone,

I aligned two STL meshes using the **"Align (point pairs picking)" / partially aligned objects** workflow in CloudCompare. After the alignment, I would like to evaluate the RMS error only in specific regions of the meshes.

My first thought was to crop the meshes after they were aligned, but I couldn't find a way to export the STL files while preserving the transformation applied during the alignment process.

Is there a way to:

1. Export STL meshes after alignment, keeping their aligned position?
2. Crop both meshes in their aligned position and calculate the RMS only for the selected region?
3. Evaluate RMS for specific regions of a mesh-to-mesh comparison without cropping the entire model?

I tried cropping only the reference (master) mesh, but as far as I understand, CloudCompare still calculates the RMS considering the entire mesh, including areas that are missing on the test mesh, which may be affecting the results.

I'm working only with meshes (STL files), not point clouds.

Any suggestions would be greatly appreciated. Thanks!

So for '1', as soon as you export the aligned mesh to STL, it should be saved with the transformed coordinates. So it should keep its aligned position.

For '2', you can use the scissors tool, but you might want first to sample points on the mesh to be able to make a finer selection. Then, compute the distances between the cropped mesh (or cropped sampled cloud) and the reference mesh. Then use the 'Edit > Scalar fields > Compute Stat. Params', choose the 'Gauss' distribution, and you'll see in the Console several statistics, one of them being the RMS.

And for '3', there's no direct way to do it.