Hi there.
I believe there is a bug with rendering a vray light as visible with a directional value > 0. The higher the directional value the darker the light renders when viewed through a refractive material.
- In Vray Next the light renders correctly when not viewed through a refractive material.
- Using Vray 3.6 the light renders darker whether through refractions or not.
The attached images explain it better.
Justin
It might be wierd, but actually the physically corect behaviour is the one in 3.6. Vlado has a short video showing this in real life 25 reactions · 11 comments | Lon went to a camera rental place today and I took this video in the meantime. An egg crate light diffuser is probably the best explanation of why directional V-Ray lights look darker when you look at them from the side. Apparently they are used in real life to give directionality to otherwise diffuse emitters. | Vladimir Koylazov 
We have changed this to show the full light intensity for the camera rays in V-Ray Next by popular demand and we have request to change this for the refraction/reflection rays. However, doing this might effect how the light work by effectively making it non-directionaly. Long story short, we have this as something that we should work on and it is in the todo list.
Best,
Blago.
I’m guessing the “correct” 3.6 version is replicating the look of what a honeycomb grid would do to a light. In some situations this would be desirable I guess. Would it be possible to just include it as an option in the light settings?
Just watched the video. Exactly as I though. The honeycomb grid effect. The problem is that some ceiling downlights for example have a specific angle of illumination and they don’t use honeycomb grids. Short of using an IES light instead, having the option of whether to use this effect or not would be very useful.
Yep, looking for a general solution is in the todo list.
Best,
Blago.
Thanks for the response.
would be nice to have this darkening effect as an option in the light setting. Any update on this?
I just posted this too, and it’s still present with the latest vray. I mean it’s making it not usable in the scene I have where I use vray light as visible LEDs. Indoors they look like black LEDs.
Just encountered this issue as well. At first I thought it was a bug but then that it might be correct behaviour and after seeing Vlado’s video above it appears it is! Should be able to work around it for now but an option box to keep visibility in reflections/refractions would be handy
