Why are surfaces created even where there is no point cloud?

[ken＠67]

When I applied Poisson Surface Reconstruction, the surface are created even where there is no point.
The black area shows point clouds.
Why are surfaces created even where there is no point cloud?
Why the surface converges to a rounded shape?
Could you recommend an article or where should I get the theoretical guide?

[daniel]

Yes, the Poisson Surface Reconstruction algorithm creates a closed and continuous surface by default.

But there's a way to clean that afterwards: see the documentation: https://www.cloudcompare.org/doc/wiki/i ... n_(plugin) (especially the "Using the output density" section).