unfold / unroll cylinder and point cloud

[andre8_l]

Hello,

I am trying to unroll a tower point cloud which I collected using a laser scanner. The issue is that the tower has a very particular shape: it's a truncated cone with a cylinder on it.

I divided the two surface but through the specific unroll tool I had not good results, is it even possible to obtain something?
Any suggestions?

Thank you,
Andrea

The attachment the tower.PNG is no longer available

The attachment cylinder shape.PNG is no longer available

The attachment truncated cone.PNG is no longer available

cylinder shape.PNG (290.47 KiB) Viewed 2954 times

The attachment unroll up view.PNG is no longer available

[daniel]

Well, actually these tools have been originally added to CloudCompare to do the exact same thing (and the conical shape was even more conical). Of course you have to set the right axis point, and make sure the cylinder /cone axis is aligned with X, Y or Z. And the last tricky part is probably to guess where the cone apex is.

Don't hesitate to send me the cloud (admin [at] cloudcompare.org) so that I can try on my side.

[daniel]

For the records, thanks to Andrea's files I was able to fix/improve the unroll tool. This is available in the latest 2.11.alpha version.

One can now set the angular range of the unroll tool for all modes (i.e. also the conical projections).

Otherwise, the former 'straightened cone' mode has now two flavors (with 'fixed radius' as before, or with a corrected radius based on the theoretical cone shape).

Here's the result:

UnrollCompensatedRadius.JPG (153.13 KiB) Viewed 2883 times

P.S.: mind that the unrolled clouds are not at the same height because the 'cylinder unrolling' method uses the Z altitude directly, while the 'cone unrolling' method uses the curvilinear abscissa (starting from the cone apex). It's easy to manually reposition the unrolled cone if necessary.

[muzo583]

Hi Daniel,
Could you provide a reference for the mathematical background of this application? And if possible, can we save the unroll parameters after processing point cloud and then roll the point cloud back?
Bests.

[daniel]

Hum, there's no documentation apart the code itself:
https://github.com/CloudCompare/CloudCo ... .cpp#L3656
https://github.com/CloudCompare/CloudCo ... .cpp#L3671

And there's no way to re-roll the cloud currently either.

However, the 2.13.beta version gives much more options, and especially the option to use an entity to 'read' the parameters (axis, radius, etc.). So it may be a way to save most of the parameters between 2 sessions of CC (simply save the cylinder or cone entity as a separate .bin file).