Problem rendering with 1.50

[nate]

Hi,

I'm having some trouble rendering with VRay 1.50 SP1 and wondered if anyone could help. (See attached, full render and render with maps and reflections turned off)

I've narrowed the problem (black and white artifacts - lots!) to imported models, in the instance below the offending articles were the tables tops, once remade in that scene everything rendered OK. It doesn't seem to matter if the models were made in Max 8 or 9 and ones that work in one scene will cause a problem in another.

So far I've been lucky that the models have been simple to replace, but as well as the time taken to do test renders hiding different objects to find out which is the problem, I'm dreading the day that I'm on a tight deadline and have to remodel something complicated in the scene.

These were the renders settings (for high res I upped the irradiance to 40 subdivs, sample look up to best and whacked the LC up to 1000). These settings worked OK, without this problem in 1.47 (QMC instead of DMC), but I can't imagine this is a bug as no-one else on the forums seem to have the same problem.

What am I doing wrong? Any ideas gratefully received!

[rivoli]

some of those artifacts are caused by the antialiasing filter. sharpening filters like mitchell can cause them, you can either change filter type (or turning off filtering altogether), or check clamp output and subpixel mapping.

not sure whether it sorts everything out though, there seems to be a lot of odd stuff going on there.

[vlado]

Also, check the visibility of VRayLights in reflections/speculars - it looks like there is a light that is reflected in the materials in the 1.5 version, but not in the 1.4 one.

Best regards,
Vlado

[nate]

I could definitely with improving my work in general so I'll give some different anti-aliasing filters a try but the main thing is that the problem seems completely reliant on imported models.

Both of the previous images were done in 1.5, just less mess with reflections and maps turned off.

Here's another example which is probably a bit clearer, a different scene to the previous, the first image has an imported table (3DS file) which is causing some strange disco effect. The second image shows everything exactly the same (same lights, scene, materials, settings etc), the only difference is that this table was made within the scene.

Also, not every imported model causes this problem but at least one model in every scene does. It doesn't make any sense to me.

[vlado]

If you wish, you can send me one of those models to vlado@chaosgroup.com for investigation on what is causing the issue. Do you also get any warnings in the V-Ray log file?

Best regards,
Vlado

[nate]

That would be brilliant, thanks Vlado. I'll send them through tomorrow when I'm back at work.

[DaForce]

Yeah that level of problem (last image) would almost definitly cause something to show up in the vray log.
well worth checking.

[RErender]

I have seen similar issues on objects with bad UVW's, if you if you put a new box UVW on the objects does it fix it?

[nate]

OK, these are the warnings that I get in the VRay log:

Warning: Subpixel colour mapping is on: rendered result may have incorrect brightness.

Warning: Camera matrix is not orthonormal and 'Max-compatible ShadeContext' is ON

Warning: Standard materials and lights may shade incorrectly

I get these for both the good and bad image but with the bad image I also get:

Material returned overbright or invalid colour (object "foster tab",RGB: 1.10197e+025 0 9.58658e+010)

I didn't use a UVW map for either image (because the offending model is just stainless steel and glass) but when I tried applying a UVW box to the bad model it didn't make a difference to the log warnings or the rendered image.

Interestingly, when I turned sub-pixel clamping off I got an effect much closer to my first posting (see below).

Could this be a mesh/poly problem. When I import the model in as 3DS file it doesn't render correctly but when I create it from polys in the scene it does?

Have emailed the model to Vlado so maybe he can pick something up. Thanks for everyone's help and suggestions so far by the way.

[rivoli]

Warning: Camera matrix is not orthonormal and 'Max-compatible ShadeContext' is ON

have you tried unchecking max-compatible ShadeSontext in the vray settings tab?
I happened to have problems with the camera correction modifier and that one on in the past.

[nate]

You're a genius!

It'll render absolutely fine with this unchecked. Thanks so much for that, you've saved me hours

[tehamnes]

I've had the same problem, especially with bathroom scenes with reflective tiles. Lots of white/black dots all over the place.
Tried unchecking reflection/specular visibility on vraylights etc etc. but the dots would still be present.
Then I set the global refletion depth to 4 or 5 and the dots disappeared! Don't know excatly why...? As rivoli mention I think I also unchecked the max-compatible shadecontext at the same time, so one of the two fixed it.

[rivoli]

It'll render absolutely fine with this unchecked.

glad it helped. I struggled with that one myself once

[nate]

easy when you know how!

[DaForce]

yep, the vray log really is worth paying attention too