Trying to convert a scan of the inside of building from points to mesh

[Ricky]

Hi there,

first off: I am new with cloud compare, please bear with me.
I have a 3D scan of the inside of a rather large building. We used the Leica BLK360. I thought the built-in software could automatically transfer the point cloud into a mesh. Someone else did the scanning, I am unsure whether this person failed to do the exporting to a OBJ/STL or not.
Anyway, I am stuck with this point cloud for now. The output is supposed to be used for measurements for different artistic installations, planning basis for the artists etc.

What I did so far:

- calculate normals
- poisson reckon surface reconstruction

When exporting one or multiple (there are 23 individual meshes) and exporting them I can choose between: .bin .fbx. dxf .shp

When exporting to a .fbx files it seems like the output is "solid" but I need it to be hollow.

It feels like I am close but not entirely there. Is there an option to directly export to .stl or .obj? Why is my output solid? Will it be solid when exporting to one of those two formats? If yes: How do I make it hollow?

If you guys want to look at the file, its here: https://drive.google.com/file/d/1jbsUts ... sp=sharing
But be warned, its size is 2.48GB

Kind regards, I appreciate any help!
Ricky

[daniel]

Ok, thanks for the dataset, it's always easier to understand with data!

0) The normals are quite clean. I haven't checked them all, but the ones I checked were good. You can probably use a slightly larger radius if you want a smoother result.

1) Then, you have to merge all the clouds before computing the mesh. Otherwise, the Poisson Recon algorithm can only use very partial data and will reconstruct each cloud independently... And you'll end with a collection of mesh that don't fit together
--> See https://www.cloudcompare.org/doc/wiki/index.php/Merge

2) Due to how wide the cloud is, I used a reconstruction depth of 11. You could get a more refined result with level 12, but then you'll get a very large mesh (I already had more than 15 million triangles).

3) I then used the output "Density" scalar field, to remove the triangles that are too far from any point, and might not be correct (I'll let you play with it to see where you want to actually set the threshold):

first_poisson_mesh.jpg (250.83 KiB) Viewed 184 times

4) You can then use 'Edit > Scalar fields > Filter by value' to create a new mesh (use the 'Export' option to create a new mesh with only the visible triangles)

5) You can remove the scalar fields on the resulting mesh (Edit > Scalar fields > Delete all!)

second_poisson_mesh.jpg (162.46 KiB) Viewed 184 times

inside_poisson_mesh.jpg (176.94 KiB) Viewed 184 times

6) Eventually, you can export this mesh to any format you want (PLY, OBJ, STL, FBX, etc.). Mind that only the PLY and FBX format can keep the colors, as they are 'per-vertex' colors. Poisson Recon doesn't generate textures that could be associated to an OBJ file. And STL doesn't support colors at all.

[Ricky]

Ok wow. This just worked. I am super impressed!
Thank you so much Daniel, that has been super helpful ❤️

[Ricky]

Ok it seems that the colors are not exported as with a .fbx file.

I tried edit -> scalar fields -> convert to RGB and re-export that still resulted in a gray object. Do you have another hint for me?

Kind regards
Ricky

[daniel]

There might be tools that are able to read meshes with per-vertex RGB colors and then convert these colors to textures? Maybe Blender as I believe it can read PLY files, and probably FBX?

Sorry, not the expert in meshes ;)