We all know the issue with VRayLights and directionality seen through reflection/refraction. Now we have something ready as a fix, but it comes at a price - the light beam looks different.
At the example below - plane and two disc lights with directionality set to 0.94 / 0.85 / 0.6 respectively. Left image is the old method, right one the new GGX light distribution.
I can provide a build for those who want to test it locally (V-Ray 6 license required).
Eager to hear your thoughts!
Cool if it fixes that bug. I don’t mind the different shape a bit.
Is the previous light distribution physically wrong? (Is the new GGX light distribution more physically accurate?)
Compatibility should be fine if there is a switch to revert to the previous light distribution.
Same question as flat, which is the more physical correct distribution? For me I don’t mind though as long as the bug is fixed
Both distributions are correct (they are similar to adding an IES profile to a light), however with the GGX-like distribution, the light is not so dark when viewed from the side.
Best regards,
Vlado
Can we still get full directionality with the new method? In other words, what about a value of 1.0 ? It is already difficult to control when you want a very directional light (by difficult to control I mean we have to use many decimal places to make small tweaks once we get close to 1.0. Rarely do we ever want a true 1.0, but we often want the light o look a heck of a lot more like a spotlight, and tweaking fine values between 0.98 and 1.0 is touchy.
The new GGX lights look great to me, perfect for washing up the sides of buildings at night etc. I presume there will be a “GGXness” spinner to set it as required? Or is it just an on/off tickbox? I’m hoping for the former!
@matanov I wonder how this new behavior affects the direct visibility of the lights source, if at all. Talking about the usual problem of area light being shown as black square/circle in render, if the directionality is too high and camera is outside of that solid angle. It`s annoying to deal with, adding another piece of geo under with light material and all that. So i wonder if with this update we still going to see black area. I understand the reality vs the cg approach difference of the phenomena, hence why it`s black. I think artistically, people expect to see source as something bright, even at low glazing angles. Thoughts?
We are still experimenting, but yes - in this implementation the camera angle is still affecting the looks of the source. @GLASS-CANVAS - yes there is a GGX spinner in this variant.
So this is still not in Vray6 hotfix3? I just installed it and my LEDs are still black behind the glass.
No, it’s planned for Update 1 (V-Ray 6.1).
Oh I see. Thx
it’s not in update 1 
No, not yet as we changed the original approach to something that seems to work better and there wasn’t time to fully implement it for Update 1.
Best regards,
Vlado
Hi, any update on this? is it implemented in VRay 6?
Hi, are there any papers on directionality of rect light? I’m doing simulation of this with real time rendering, but it’s not so good for now.
Probably coming in 6.2. Anyone with a problematic scene is welcome to send it over for a test.
Looking forward to this. Thanks.
