M3C2 input Parameters

[Linzoid3000]

Hi Daniel,

I have two questions about the calculation of the default input parameters.

1. For the core points, the value doesn't have a unit. What is the unit? The same as my data, meters? Is it a search radius? One core point in each 0.254m radius? Or is it a proportion? For example, 0.254. Can I consider this 25.4% of the full cloud? How is this value chosen?

2. How are these default numbers chosen? I understand that a user may adjust the normal and projection scales (D and d) depending on the heterogeneity of the input data to adjust the sensitivity. So I wonder how these numbers are chosen when I allow defaults.

Thanks in advance!!

Lindsay

[daniel]

1. Yes, it's the minimum distance between two core points (we simply use the 'Subsample" algorithm to select the core points - see http://www.cloudcompare.org/doc/wiki/in ... CSubsample). The units are the same as the clouds.

2. By default it's only very random guesses, based on the size of the clouds bounding-box (like a given percentage). And if you use the 'guess params' buttons, we make some random samplings, and we try to guess better parameters. However it's still approximate and random...

[Linzoid3000]

Thanks Daniel!!

[Soundous.Bellout1994]

Hi Daniel,
I hope you can help me.

I just started to work with CC, and I need a signed distances between comparated clouds.
I have read that it works with a plugin M3C2 but it's not activated.

I don't know how to activate it or to download it. I hope you can help me.

[daniel]

You'll need the Windows version probably (or the latest Linux and MacOS versions maybe).

And of course you'll need at least 2 clouds that you must select in order to enable the plugin.