V-Ray Light, Affect Specular/Reflections - Getting old behavior back?

[JonasNöll]

I think the option to control reflections and specular independently in V-Ray lights has been removed in later V-Ray versions.
Before you could have for example have a domelight emitting specular and a totally different geometry just show up in the reflections.
Now if you do this the geometry shows up in the reflections but the specular from the domelight is being totally removed.
Or you could have 2 domelights, and controlling reflection strength and specular strength independantly.
Also now the Affect Reflections button apparently has no effect? And The Affect Specular just enables or disables both?

What is the reason for this and why is this the preferred way now?
And is there any way to get the previous behavior back in V-Ray 5 to support scenes set up previously and get consistent results?

[vlado]

The old behavior was not physically accurate as the specular from a dome light did not always match up with the reflections and this prevented some optimizations that I wanted to implement. In addition, the new behavior matches that of other render engines as well (like Arnold, Corona, Redshift etc) which makes lighting setups somewhat more portable. Those engines have only two options - "affect diffuse", and "affect specular" which behave identically to how they work in V-Ray now.

The "affect reflections" option now only controls how the light appears in perfectly specular reflections (without glossiness). In principle, it is possible to use some threshold that determines what is "reflection" and what is "specular" (glossy). Would that be useful?

Best regards,
Vlado

[JonasNöll]

Hi,

thx for the reply. I will tell you the issue that I have and maybe you can help me come up with a solution for that specific case.
Basically I am having an issue with the way the ground projection works with V-Ray and the dome light and I want to make it behave the same way like in Corona (as described in this thread: https://forums.chaosgroup.com/forum/...orona-vs-v-ray)

So I built a setup that works perfect in my case in V-Ray 3.6 but not in V-Ray 5.

Basically the setup is like following:
- Have a domelight with VRayHDRI in spherical projection mode
- Create a dome geometry that I can scale smaller or bigger depending on my need and put a V-Ray Light Material in with VRayHDRI set to 3ds Max Standard and put a spherical UV. The UV Gizmo center represents the Tripod height of the captured HDRI. The scale of the dome geometry is the scene radius (like in Corona)
- Disable GI, Cast and Receive Shadows and only have it show up in the reflections/refractions and primary visibility.
- (Then I have an additional goundplane to catch shadows and so on but thats not important for this case)

This way I will get my direct lighting and specular from the domelight but the reflections are happening from the geometry and I don't have the distortion issues from using the ground projection in the domelight. Once you link and align everything to the light you can scale and rotate everything together. Works perfect for V-Ray 3.6 and look exactly like in Corona without those issues of the ground projection and/or too largely scaled reflections from the domelight.
But in V-Ray 5 the domelight doesn't cast any specular anymore, basically I only get the diffuse light contribution as all speculars that are behind my dome geometry are "blocked". The workaround is to put another additional light "inside" of my dome geometry have it only affect specular and put it at the position of the sun but that is less than ideal because the specular doesn't match the indefinitely far away domelight diffuse contribution and because that changes for each HDRI.
Was happy to have this setup working in 3.6 but in V-Ray 5 unfortunately because of the way things changed it is not so easility possible anymore
So any idea how to do this in V-Ray 5?

Thanks a lot

Apart from that the option to control specular and reflections independently was something that I used very frequently. For me the new way doesn't seem to offer any advantages at the moment so I just wonder if it could be switched back possibly.
Similar issue with the decision to remove the option to independently control specular and reflection glossiness in the material, but that is another issue...

[darius_wojcik]

Sorry if I use your post but for me it behaves like a bug and not a physically accurate feature.

I have already created a ticket for this. This change affects 350K images per month in our system. And for me it makes a difference if I see the light source in the reflection or not.

In the screenshot you see what I mean. Where do I have the possibility to take the light source out of the reflections?Also for me this is not a good decision to remove this.

[JonasNöll]

darius_wojcik: It apparently disappears if you also put "Invisible" and disable "Affect reflections". In previous versions everything made more sense for my understanding, you can have it visible but still chose to affect affect reflections or specular independently.

[PIXELBOX_SRO]

i second all the posts its absolutely legitimate request to have this back.
no idea where this comes from...could be beacuse of the lightmix having issues with the old setup.

[darius_wojcik]

Thank you very much for your answers and excuse my "DeepL english"

JonasNöll Well, until now the invisible checkbox was only for "invisible to camera" and not "invisible to reflection". I controlled that with "Affect reflections". You still have a weak specular light but that was ok.

My guess is that the Vray version was compiled for 3D Max 2021? If I compile the same scene in Max2019 and render it with Vray3.2, it works. But Max2021 and Vray3.2 causes problems.

I really hope it is a bug and not a new feature. We have over 1000 carpaint materials that are not working now. We have 1200 car 3D models that need to be revised. That would be a small catastrophe for us.
And at the moment I don't see any alternative to shut off the light source from the reflections.

[vlado]

Hey Jonas,

Here is a setup that I think is similar to what you need in V-Ray 5. Does it work for you?
https://drive.google.com/file/d/18BA...ew?usp=sharing

Best regards,
Vlado

[JonasNöll]

Hi Vlado,

thanks for the file but from what I can tell this one has exactly the issue that I was talking about.
As soon as there is any light "behind" the geometry dome, all the reflection and specular will be ignored.
In 3.6 I can just disable the cast shadow in the geometry of my dome and would get the specular (for example from the sun) and the reflection.
In VRay 5 as soon as the light is "behind" my geometry dome (which a VRayDomeLight always is) it will only consider the diffuse lighting but not the specular anymore.
I attached 2 pictures to hopefully demonstrate the issue:


Added a new Omni Light and put it near the teapot. The light is "inside" the geometry dome. A specular appears on the teapot as you would expect.


As soon as the light is moved outside the dome the specular gets removed on the teapot. In 3.6 this is no issue.

If the problem doesn't really get clear I can prepare a comparision to you for 3.6 and 5 with a more realworld scenario (car on a parkinglot with hdri lighting) where you can see the difference between both. In 3.6 using this setup I get the yellow sun specular from my sun and all the shaders look nice. In 5 basically it is just the same as I ONLY had the dome with no domelight emitting specular. It is possible to "fake" it by putting a light "inside" the geometry dome and moving it manually to the position of the sun in the projection. But that is very inconvenient compared to the approach before where you can just swap out the HDRI and the specular is at the right position. Also because the diffuse light from the domelight is infinitely far away and the specular light "inside" the geometry dome it has a different appearance...

[vlado]

As soon as the light is moved outside the dome the specular gets removed on the teapot.

I can't see your images for some reason, but I'm not able to reproduce this. In my scene, I've added an Omni light outside the dome and it seems to produce a specular highlight on the teapot (see the attachments).

If you use a VRayLight outside the dome, then you'll have to modify the scene slightly - replace the self-illuminated VRayMtl on the dome with a VRayLightMtl material that has zero opacity (f.e. with a VRayColor map set to black) and make the dome light invisible. Here is the modified scene: https://drive.google.com/file/d/1cu2...ew?usp=sharing

The V-Ray 3.6 behavior is not coming back, but I'm trying to see if we can provide alternative workflows to do what you need.

Best regards,
Vlado

[JonasNöll]

Hi, somehow the forum doesn't let me upload any pictures anymore and I uploaded them on my webserver:

The pics from before:
https://www.jonasnoell.com/downloads/vray/spec1.jpg
https://www.jonasnoell.com/downloads/vray/spec2.jpg

Comparrison in my setup between 3.6 and 5.
https://www.jonasnoell.com/downloads...omparrison.jpg

I will check out the new file you sent and see if this fixes my issues in the meantime

[kosso_olli]

The V-Ray 3.6 behavior is not coming back, but I'm trying to see if we can provide alternative workflows to do what you need.

Well, I just can not shut my mouth about this one: What would help Jonas (and me) immensely, would be the addition of a way to control the upper half of the dome light, as requested years ago and debated on 9 pages in a recent thread nobody cared to answer, except for Lele.
That way, the workaround with the sphere geometry here is not needed and this problem would be gone.

[vlado]

I'm having this in mind and I have some draft implementation already. I did not see (and still don't see) any particular reason to jump in that thread - as you pointed out, we've already discussed this before.

Best regards,
Vlado

[JonasNöll]

Hey unfortunately I can't confirm that this works. Weird stuff is happening, but definitely not what I would expect. In your setup, Vlado if you boost the Affect Specular Value it would also overlay both reflections (The one from the domelight and the one from the geometry)
In my scene if I put a VRay color in my LightMaterials Opacity it will become transparent and change the whole look. I found out that it then overlays the background color. If i switch the background color to black it looks similar but the refraction of the environment in my carwindows becomes totally messed up.
Also the yellow specular of my domelight still doesn't show up.

So basically I just have a HDRI with a strong sun. I only want to use one light in my scene which is my domelight.
The domelight should be responsible for the diffuse lighting and the specular highlight of the sun.
And my geometry dome should be responsible for the reflections of my environment and the primary visibility.

In V-Ray 3.6 that is very streight forward. I'm hoping that there is also a way in V-Ray 5 because that would improve the issues that we are having with the domelight ground projection
Basically the issue as kosso_olli said is still the same, I just want to have a setup that works as easy as in Corona.

Thanks for the help, appreciate this

[vlado]

Ok, in that case it would help if you can send me an actual scene to look at to vlado@chaosgroup.com; there's obviously more stuff in it that in my simple test. If you tell me what is your 3ds Max version, I can also get you an experimental build where the dome light has a radius and behaves similarly to Corona.

Best regards,
Vlado