Why Front view surace dark in one rhino and light another and odd reflectance


I have a surface facing me in Front view, its almost black, make view Back view and I see the colour I had hoped it would be.
files attached.
I copy paste it to a new Rhino V5 and its the colour it should be.

I have not done anything at all to lighting, I never touch lighting. so why is this ?

It is the size of my model so I cant view plans or see my darker lines !!!

Furthermore the surface looks somewhat bent and bashed given the reflections, yet its an extruded curve which is two straight lines with a shallow BlendCrv created curve between, and the V shaped light patterns occur on the straight bit !

I do find the V5 reflectance odd when I also make flat surfaces. planar surfaces seem to have curvature !
FrontViewsurface light yet dark in another project.3dm (63.2 KB)
FrontViewsurface dark.3dm (103.9 KB)


In the first example you have display mode: Ghosted in the other you have display mode: shaded.

The middle part of the surface have positive curvatur so it is not a plan surface, that could explane the ligth.

Håbe that helped

Ah yes, silly me !