lighting problem Vray 2.40.03

[emonimo]

Hi,
I recently changed to a new workstation, and I was rendering an old scene just to test speed, when this anoying surprise came to mi image. Here you can see the diference between the two renders. The one that looks ok is rendered in my old machine with Vray 2.3 and the one looking really strange is the rendered in the new one with Vray 2.4... Does anyone had a similar problem?... is there any solution?
The material of the lamp is a simple 2sided material with no refraction, just some reflection (the geometry has thicknes), and the light is a Vray sphere light with the same settings in the two renders. Both rendered with Brute Force.

[voltron7]

Hi...i have noticed that since a certain build I cannot recall, a lot of times normals are wrong and it's really annoying.
It seems like it is random, too, and happens on standard max primitives, edited polys, and especially on lathe modifiers and mirrored instances...
No real solution, but try reversing normals. Also, u can check that by using an override material with the vraydirt+vraylightmtl setup.
backward faces and double faces show up as pure black...there are many write-ups/tutorials about that material, too. I think Ronen B. has a good one.
Can't say if it's V-ray or 3ds max as it seemed to start for me when going from max2012 to 2013.
HTH

[vlado]

Hi emonimo,

Can you post that scene? If there's a bug I'd like to fix it before the next update.

Best regards,
Vlado

[emonimo]

Thanks for your answers, Voltron and Vlado. I have tested a few things and nothing worked... the geometry as I said has thicknes... its a line with Lathe and Shell modifier, so I think normals are not the problem.

I cant post here the scene because it has some copyright material in it, so I have send it to you, Vlado, via email.... to vray@chaosgroup.com... Is there any problem with this method, please let me know.

Hope you could find the solution to this.

[emonimo]

I forgot to say that changing the lamp material to a Vraymaterial with some glossiness in its refraction works perfectly (but longer rendering time)... the problem appears when using 2sided-material

Edit: with no shell modifier in the geometry (no thickness), it also works nice... the problem is the 2sided-material with thickness... hope it hepls

[Neilg]

Edit: with no shell modifier in the geometry (no thickness), it also works nice... the problem is the 2sided-material with thickness... hope it hepls

I was under the impression that the 2 sided material was made to be used with geometry that was single sided - no thickness.

[voltron7]

I was under the impression that the 2 sided material was made to be used with geometry that was single sided - no thickness.

second that ^

[tashko.zashev]

Hi,

It's seems that this is a light cache issue and enabling "Retrace threshold" parameter will helps for this case.

[emonimo]

Thanks for you quick answer... I've been really busy, and havent got time to test... tonight I'll check the ''retrace threshold''.