Vraylight (the object itself) casts unwanted shadows.

[samuel_bubat]

Hi there,

I have a light setup like this.

A ground plane and several vray lights. All the vray lights are set to "include" various objects.
The groundplane is lit by a simple white from the vray Environment Dialogue. No Vraylight Affects the groundplane.



In the rendering, the light sources seem to to cast shadows from the environment on the ground plane.
A pretty undesired effect. Anything that can be done about this in the short term, without ripping the scene
apart in various layers ?

[vlado]

Are the lights set to "invisible"? Are you using GI or ambient occlusion? In any case, a work-around might be to use the a dome light.

Best regards,
Vlado

[rivoli]

I was really intrigued by this one and just had a quick try. the lights don't seem to actually cast shadows on the ground, they rather make darker what they should cast light on, if the object is excluded. if you make them double sided you'll see the "shadows" going both directions.
using a dome light instead of the environment seems to help a bit, but the problem is still there, even if fainter. weird.

edit: well, it seems related to gi, if you turn it off the problem disappears.

[samuel_bubat]

Yes, all lights are invisible. I´m using GI BruteForce/Lightcache but it happens with other GI methods as well.

[vlado]

Hm, ok. Another option would be to put a VRayColor texture on the lights, and set its alpha to 0.0 so that they are completely transparent, but still emit light.

Best regards,
Vlado

[rivoli]

the workaround mostly works, but not completely:

[samuel_bubat]

Yes, this works more or less. The shadow is gone , but with alpha 0 it get´s brighter than the actual groundplane, wich is not pure white in my case.


(I added this texture just to the light on the left)

I can adjust the alpha and get a nearly clean result at around 0.3.
But it ´s still not perfect. It somehow looks a bit dirty in this area.
Anyway, for the preview today it will be ok.

Thanks, that was a quick solution !

[vlado]

Ok then; I made a note to look into this anyways.

Best regards,
Vlado

[samuel_bubat]

There seems to be a bit more wrong.
It looks like the include/exclude is not working properly.

Some images.

Standard Vray Light, nothing excluded, visible, multiplier 30


Same settings as above, but the plane is excluded
But there is still light hitting the plane.


Same as second image, only the light is invisible now.


Multiplier turned down to 1
These are the shadows I experienced earlier

[vlado]

Yep, that's how it works right now. Will be fixed of course, but for the moment there isn't much else to be done.

Best regards,
Vlado

[samuel_bubat]

Yep.. no problem, just wanted to give you all the infos, maybe it helps.

[vlado]

Hehe, yes - thanks!

Best regards,
Vlado

[chrisjacks21]

Interesting, I have always wondered about the unwanted shadow when excluding lights from floor geometry - I have had this problem when using VRay lights positioned close to the floor in a studio car render setup.

[cgrande]

Yep, that's how it works right now. Will be fixed of course, but for the moment there isn't much else to be done.

Best regards,
Vlado

So is this being solved for RT in the next update in December 2011? Seems to only be an issue for me when using OpenCL. CPU doesn't cause these mysterious shadows. AKA Ghost shadows.

[vlado]

Hm, not sure - can you show me an image?

Best regards
Vlado