Using Background color (from Environement)

[kostenurka]

Hi,

From vray2 I'm used set my background color from environment slot to white for having simple white background. I'm trying same technique in vray3 but white color with multiplier 4 seems to illuminate my scene which is not what I want.
I expect to illuminate my scene independently from the background by using dome light.

Do you know how Background can be only a background and not source of light?
thank you

[Grigio18]

Hi,

From vray2 I'm used set my background color from environment slot to white for having simple white background. I'm trying same technique in vray3 but white color with multiplier 4 seems to illuminate my scene which is not what I want.
I expect to illuminate my scene independently from the background by using dome light.

Do you know how Background can be only a background and not source of light?
thank you

Try to add a black color in the environment overrides, you can override gi, reflection, refraction and matte separately.

[Peter.Chaushev]

The only ways the Environment Background will leak illumination through a Dome Light is if the Dome has been set as a Hemisphere instead of a full Sphere or its "Affect (..)" parameters are disabled.
Additionally, keep in mind that anti-aliasing of edges bordering the background will look unfiltered if the Background intensity is higher than 1. This gets progressively more pronounced the higher the values are.

Try to add a black color in the environment overrides, you can override gi, reflection, refraction and matte separately.

These override options only alter how the the Environment Background affects the scene. They do not override the GI itself (or global Reflections/Refractions/Matte). If a Dome Light is properly set, the Environment overrides will have no effect no matter how they are set.

Kind regards,
Peter

[kostenurka]

Thank you for answering. The configuration above works. Now I have pure white background in combination with wrapper floor.
I've set my HDRI on GI (skylight) slot. If now I set a domelight with HDRI it works as a double light source independently from my GI slot. How can I connect my domelight with my GI ? Is it actually recommendable anymore (like it was in vray2) to use dome instead of GI ?
Thanks

[Peter.Chaushev]

Well, if there is a wrapper (shadow catcher) floor, first you need to make sure the Wrapper Material > Matte > Matte for Secondaries option is set to "All secondary rays". Then, make sure the Dome Light (set to Sphere preferably) is invisible (so the Environment Background is displayed instead).

You don't need a GI override. As already mentioned Dome light blocks GI illumination if it is a sphere.
If it is a hemisphere, the Dome block GI from half the Environment (in which case you would need to set up a GI override with a copied hdri texture from the Dome Light to compensate for the other half).
You don't actually get a double light source by using same texture for GI and Dome Light. If you wish to increase the Dome light illumination, simply increase the light intensity. Also, in most cases you would want to match the overrides and background intensity values (as well as Dome Light's).
Also, depending on the scene, consider using the post-production VFB Exposure tool instead of increasing the background intensity value to minimize the negative effect background intensity can have on anti-aliasing (which I mentioned in the previous post).

You would still need Reflection/Refraction overrides (again, copy the hdri texture from the Dome Light) to properly render the scene objects, otherwise they will be affected by the wrapper plane.

See the following screenshots - the scene consists of a shadow catcher plane, a Dome Light, and 3 spheres (front 2 polished chrome, 3rd one is glass):
1. Dome Light is invisible. Background uses the Dome Light hdri texture. No overrides needed.
2. Dome Light is invisible. Background is set to white color. Reflection/Refraction overrides use the Dome Light hdri texture.

Kind regards,
Peter

[SHoutzager]

I was just working on the same thing (controlling global reflections)! So I was able to get reflections with a dome light and could control that dome light to some extent. A few questions.

1. How can I pivot the hdr image that the dome light uses?

2. How do the Envirorment Override settings work? I put a bitmap and an hdr image in the reflections override and it never made a difference. Again I am trying to control what is being reflected into the whole scene.

Could you make the files available Peter? I am still getting a matte black floor that i set with a Wrapper material.

[Peter.Chaushev]

Hello, Steven,

You can control the hdri projection in two ways - either by manually rotating the viewport widget (see "Use Transform" https://docs.chaosgroup.com/display/...tDome-Settings) and/or through the TexBitmap's UVW controls (https://docs.chaosgroup.com/display/...mentParameters)

As for the Overrides, by default, V-Ray uses the Background color/texture for GI, Reflections, Refractions, and Secondary Mattes (make sure texture's mapping is set to UVWGenEnvironment). To have one color/image for background, but another for, let's say, material reflections, you can manually change that aspect of the background functionality using the specific Environment Override.
GI based on the Background or Override color/texture slot, does not have any effect on the scene if a Dome Light is set. This is due to the Dome essentially encapsulating the scene (and even if the light is set to invisible, it still overrides any skylight illumination).
To have illumination from Dome Light but reflections from the Environment override, you would need to disable the Dome Light's "Affect Reflections" checkbox.

If you wish to use override settings only for specific materials, such options are available in the Material > Maps > Environment Overrides section (https://docs.chaosgroup.com/display/...nmentOverrides).

The Wrapper material I used as shadow catcher is Preset library > Diagrammatic > Matte Shadow Receiver (https://docs.chaosgroup.com/display/...rials+Category). Make sure to set Matte for Secondaries to "All secondary rays".
If your Wrapper material renders completely black, it probably means you have not slotted a base material within.

Kind regards,
Peter

[SHoutzager]

I used the Matt Shadow Receiver material and set the matte for Secondaries. I am still getting a semitransparent black. What base material do I need? I just created a generic base and attached it without setting anything.

[Peter.Chaushev]

A generic material would do (unless you want to simulate shadows on a specific surface).
The result you show is probably due to a mismatch between the Environment and Dome Light intensities (Environment having a lower value). Make sure they match. The same goes for any Overrides you use, unless you want to purposely make, let's say, reflections stand out.

Kind regards,
Peter

[SHoutzager]

Got it working!! I had to turn GI off. Then the intensity of the dome light and the background image I used had to match.