CloudCompare forum

Dear all,

I have a question about the parameters to calculate the normals in the M3C2 plugin. I want them to calculate manually because I have a big difference in distance when I use the normals of Cloud1 (Edit, Normals, Compute) than when I use the 'guess param' in the plugin.

I have 2 cubes of 15 cm by 15 cm. My first pointcloud (reference cloud) has 13.000 points, the second 580.000. Which values should I use for the Normals Scale and the Projection scale? And what in the case when I analyse two planes?

Thanks.

Hi,

the Guess parameters should be used very carefully. It's here to have a set of parameters that would make the plugin run, but they are certainly not optimized.

I don't fully understand all aspects of your problem. For the normal and projection scale, it's not really about the number of points, but the point density and the typicaly scale of your object. Could you give us more info on your point spacing and the size of your cube ?

Given the difference in the number of points, you should use the smallest point cloud as your #1 point cloud to speed up the calculation.

Dimitri

Hi Dimitri,

I have two pointclouds of the same cube of 15 cm by 15 cm by 15 cm.
The density in cloud #1 is 18pts/cm², the density in cloud #2 is 1282pts/cm².

Regards,

Yannick

Hi Dimitri,

Can you tell me which parameters I should use to calculate the normals in M3C2 given the pointdensity above? I want to know the signed distance between the two pointclouds, which would be zero in theory.

Thanks in advance !

Kind regards,

Yannick Vandenbroeck