CloudCompare forum

Hi Daniel,

first of all I want to express my appreciation for you and your coworkers for writing this advanced program.

I am testing the 2.5D volume estimation and I could use any information about how to find a good grid spacing. I have tried to insert different values obtaining different volumes every time. So, what I would like to understand is what would be the best grid step value to insert for my cloud.
Surely, this information can be found in the report panel as well, however I need some extra explanation about the statistics.

Thanks,

Giuseppe

Hi,

In fact the smaller the grid step is, the better the approximation will be. However, for small step values you'll generally get holes... which are not good for the approximation of the volume. You can of course try to use the 'interpolation' filling strategy to cope with that issue. But it depends on the size of the holes and how smooth is the real surface.

Anyway, assuming the clouds are regularly sampled, a rule of thumb for the grid step would be:
- compute the average "2D" surface of a cloud by simply multiplying the X and Y dimensions of its bounding-box (S = DX * DY)
- divide this surface by the number of points (S / N)
- compute the square root of the per-point surface to get a first approximation of your ideal grid step

Hi Daniel,

I tried the Volume function as well. I think it works very well! However, the Background color changes from black to white when closing the tool.

Another suggestion would be to make the resulting grid values available as a scalar for better cross checking

Thanks for the feedback.

The color bug is fixed (I've updated the online 2.6.3.beta version).

And I'll add your suggestion to the TODO list (however the scalar field will be exported with the grid points - i.e. as a new cloud as the values are computed on the grid only).

Hi Daniel,

I am using this opportunity to kindly ask you if there are any plans to realise your thoughts on exporting the cell values in the near future releases?
I am just asking because this would be really helpfull to visualise deformations - not just where they are but also which kind of deformation.

Best,
Sascha

Okay that's done. The updated 2.8 beta version is online.

I simply export the grid as a point cloud. You'll see that the points altitude is therefore the difference of height (and neither the minimum or maximum height). Hope this helps nevertheless...

Daniel

awesome!
Thanks a lot!

I am still getting the 2.5D volume bug in version 2.10 alpha release
Where i get asked to use 2 point clouds error. where as in the older 2.6.3 version it works fine so i went back to this version.
Its to bad as 2.10 Aplha version gets great acceleration from my AMD rx580 GPU

Yes, I fixed the code (I totally forgot about this glitch). However I won't be able to update the 2.10.alpha version before the end of the week.

Thanks for the feedback anyway.

Awesome thanks. I do have to say cloudcompare is an amazing program.