G2 continuity - visual kinks (Surface Normals, shading, Bug)


the screenshots shows two surfaces that meet at G2.
left: 2 single surfaces
right: joined


(parallel projection)
the situation does not improve, if the rendermesh settings are changed.

is there something wrong with the mesh normals ?
or is it a problem of the graphic card, that does not interpolate inside a mesh face in a nice manner ?

This is quite annoying, especially for first / fast visual inspection of surfaces that will be joined later.
Workaround is joining / undo.

surface_normals.3dm (3.1 MB)

kind regards -tom

Macbook Pro 16’
AMD Radeon Pro 5500M 8 GB
2.3 GHz 8-Core Intel Core i9, Mac Os 10.15.7
Rhino Version 7 (7.27.23013.15002, 2023-01-13)

systeminfo_TP_2023-01-01.txt (3.5 KB)

On Windows:

Without “Advanced GPU Lightning” on, backfaces have a slightly different shaded render:
backface
(those are 2 open surfaces, one is with positive normals, the other is hidden and with flipped normals)

Enable this:


And the backfaces will render in shaded the same way as front faces.


Tom, you have visual discontinuity because your 2 surfaces have different normals.


@stevebaer sorry to tag you (I don’t know who else works on the graphical/render part)
Are backfaces meant to have different aspect than frontfaces?
This:
2023-02-01 13_03_53-Rhino Options
doesn’t work fully, if Advanced GPU Lightning is off…

Hi Tom - the surface normals are flipped on one of the surfaces - there is a a bug track item, I believe, about this - I’ll see if I can find it and giver it a boost, otherwise I’ll make one - I’ve noticed flipped surfaces shade differently in at least some cases.
RH-69567 Display: Shaded views depend on normal direction

-Pascal

1 Like

thanks @maje90
thanks @pascal

flipping the normal of one surface with _dir
or / and
setting “Use advanced GPU lighting”

both removes the visual kink.

but looking forward to have the same shades independent of front / back face.

kind regards -tom