[deadalvs]

hi.

i got the problem witha single nurbs surface (revolved from curve) that it always renders black with a subtle reflection.

the mxm itself seems to have no problem and renders perfectly with polys.

the side corresponding to a poly's normal normally renders transparent as usual but with my geometry i get no side working. all black.

even converting the geometry to polys does not help.

any idea what the problem could be ?

i also tried simple cubes with polys and nurbs - the nurbs strangely rendered black with just a subtle reflection.

any idea ?

[deadalvs]

here's a sample:



two 5x5 cm cubes. (0.1 cm above ground); left poly, right nurbs.

both with the same dielectric material.

what could be the problem ?

[Tim Ellis]

Inverted normals?

The smoothing angle problem with CG & glass?

Tim.

[deadalvs]

do nurbs have normals ?



* * *

smoothing angle ? this nurbs cube there is a standard 3rd degree cube. that should be able to render without problems.
i guess there won't happen any smoothing.

could it be a problem with the export and advanced tesselation ?

hmm.

[Jorge Alix]

I think could be due to the NURBS has not sewed vertex as Polys, try that and you see the result, for example separate the faces from the poly cube and you'll get the same result. I think this happends in other renders.

[deadalvs]

i know what You mean.

i will try that. but mathematically it makes no sense, does it ?

[corneliu]

do nurbs have normals ?

Nurbs have normals and direction.
You can display them from the Maya menu Display->NURBS->Normals Shaded.
This plays an important role for the tesselation before render. So what you see finally are 2 rendered polygonal objects with different construction.