Normals change after importing cloud from text file

[gysvanzyl]

Hi,

I'm importing a point cloud from a text file that I generated myself. The points lie on a perfect cylinder with its axis aligned with the global Y-axis. As such, if I understand things correctly, all points should have a normal with a zero y-component. This shows the Ascii file import window with all Ny values zero.

Ascii file.png (53.02 KiB) Viewed 555 times

The import seems to complete fine, and the shaded view shows that normals were imported. However, the normals values have changed. All points now have a non-zero y-component for the normal:

After import.png (91.73 KiB) Viewed 555 times

Do I misunderstand something in how normals should behave?

Gys

[daniel]

Nope, that's 'normal'. It's because normals are compressed to save memory (they are replaced by the nearest orientation from a list of orientations regularly sampled on a sphere). Hopefully the resulting angular error should be quite small.

[gysvanzyl]

OK, thanks. Indeed, the errors are quite small. It's good to know that I've not been doing something wrong.