Sunlight occlusion issue

[Bruce Hart]

Hi Guys,
I have recently been learning Vray and have come accross a problem with a test scene. As you can see I have some fixed lights on the ceiling fans. If I make the fixed light geometry non shadow casting in the Max propeties, the Sunlight passes through it like there are no shadow casting objects above and shines a silhouette of the object on the wall. The fanlight indicated is not actually the culprit, but is behind the view.

I fixed this by making the fan lights shadow casting again, but this seems very strange and I would like to understand what is going on. The wireframe screen shot is a Sun's viewpoint which confirms that it is the sun passing through the mesh and ignoring the shadow occluding objects (the ceiling) above. I have also shifted the sun's position to confirm and tried turning it off.

Any thought's on this?

I'm using Vray 1.50 SP3a
Caustics and reflective GI caustics are off
Units are in mm/Meters
Sun shadow bias is 0.001m

The fanlight object behaves the same regardless of material applied. This was originally a Revit model, but the object is an edit poly.

Perhaps I'm missing something obvious, but I would be thankful for any help

Cheers
Bru

[Preisler]

Hi,

If you use the VRaySun then try set it to invisible.

Preisler

[Bruce Hart]

Hi Preisler,
thanks for the reply. I tried making the Vray Sun invisible but the effect is still there. Even if it wasn't, I would still be non the wiser as to exactly why this is occuring. The ceiling and roof objects are clearly shadow casting, but an object beneath them with shadows disabled allows the sunlight to cast through this object.

I made a new teapot near this area and made it non shadow casting, and as you can see, it allows some of the outside sunlight to project through it, and on to the wall. Weird.

B

[pskdude]

revit

Well in my opinion Revit and Archicad models always behave strangely when it comes to lighting. In my opinion from past expiriences if your having this many issues remodel the objects instead of figuring out why its happening. Best advice i can give.


Thanks,
Ruben

[Morbid Angel]

do all your objects have thickness? ie they are shelled.

[Bruce Hart]

Hi Guys,

I've found what this problem is from - not surprisingly it was my fault all along. I had turned down the Max transparent levels in the Global Switches Tab to 5 instead of the default 50. I have been using Mental Ray for a few years and to speed up the rendering process you tend to dial down the reflective/refractive count (and many other settings) so acheive maximum render speed. I thought that the Vray default setting of 50 transparent levels seemed a bit much.

The first thing I did with this scene was to shell the roof objects but this was never going to fix it. I have had many bad experiences with Revit geometry too in the past, and I thought this was another typical face normal problem or general Revit wierdness. The setting of 5 I had, introduced just a tiny bit of Sunlight that could be mistaken for some other problem. Being in the Mental Ray mind set, I assumed wrongly that the Max Transparent parameter applied only to refractive transparent materials.

If you were to set this value to 2 and render with Max created objects you will see the effect attached. The objects below the grey box have shadows turned off. That will teach me to fiddle about with the settings.

I've realy enjoyed getting into Vray so far - but more experiments and reading required.

Thanks for your replies