do i need sunlight if i am using dome light?

[jihao_lai]

i am using vray 6.00.01, currently on sketchup pro 2022. I know the standard rendering lighting is the vray sunlight and the default texture in the environment slot. But these days, its more efficient to use the domelight in order to eliminate the firefly effect prevalent in using the old environment slot. (still dont understand why its there). So do i still need to turn on the sunlight when using the domelight, or can i leave it off? Which option is more accurate in terms of creating a realistic photographic render? If i leave sunlight on, the shadows cast from the sunlight and the domelight differs, and the user have to match it. If i leave it off, the render lacks a strong cast shadow element. The thing that's got me even more confused on top of that, is the fact that some domelights come with a very bright spot in its texture, which the program uses as the direction of sunlight to cast shadows, whereas some simply don't. Also do i need to deactivate the environment slot when using domelight, or does the program automatically ignore the environment slot in favor of the domelight when the latter is presently used.

[natalia.gruzdova]

Hello jihao_lai,

I would like to answer by using Light Gen as an example. Have you tried using it?

You can notice that for the Exterior it gives you two options to generate: Sun & Sky and HDRI.

If you apply HDRI to your scene SunLight will be disabled by default in this case, because HDRI contains a large amount of data which can be used to emit light into a scene.
There is a wide range of HDRI maps in Cosmos Browser to simulate different environments like studio lights or outdoor lights and different scenarios like day, night, sunny or cloudy weather.


When you apply the Sun & Sky option it automatically connects Dome light to the SunLight, as a result the shadows will be matching and you will be able to control the position of the Sun in the SunLight settings. Additionally in this case you can change the intensity of the Dome light (sky) and SunLight separately to achieve the results you find fitting. Also, in V-Ray 6 there is a new feature called Clouds that you can enable in the SunLight parameters if the Sky Model is set to PRG Clear Sky.



I encourage you to try it out and see how it works and of course you can apply this logic to your own manually created lighting setups.

You can check these tutorials for more information:

• V-Ray for SketchUp tutorial — Finding the best light with Light Gen
• V-Ray for SketchUp tutorial — Creating evening skies
• V-Ray 6 for SketchUp — Customize the sky with procedural clouds

[jihao_lai]

natalia.gruzdova i understand that the sun and sky uses the vray sun plugged into a dome light; and that your default hdr setting always disables the SunLight. So my question is what's the difference between using the "sun and sky" which utilises the SunLight and the dome light, vs using SunLight and the environment slot? Does enabling Sunlight whilst using domelight (HDRI) as the main source of light make the render run less accurately or does it not matter? What if i wanted the glass panes to reflect the Sun in certain angles? I know this cant be done with domelight alone. If the Sun and Sky system is simply a domelight that uses the vray sun, could we just do it manually instead of prompting light gen to do it?

DomeLight was created to make up for the shortcomings of using the Environment slot. Does that mean the sun and sky system will eventually displace the need for using a domelight to cast environment light into the scene?

[natalia.gruzdova]

Hello jihao_lai,
I will address your questions one by one below.

DomeLight was created to make up for the shortcomings of using the Environment slot. Does that mean the sun and sky system will eventually displace the need for using a domelight to cast environment light into the scene?

V-Ray Dome Light and Environment section despite having visually similar results are different tools that do not substitute one another.
V-Ray Dome Light is a V-Ray Light that is sampled as a light source and has the same settings as other lights: intensity, units, temperature, visibility, caustics, etc. As well as some specific features like Finite Dome settings.
Environment map on the other hand is not a light source but it allows for a color or a texture to be used during GI and reflection/refraction calculations.
If you add Raw GI and Raw Light render elements and disable the SunLight you can note that Dome Light will contribute to both, but the Environment map will be visible only in the Raw GI, precisely because it is not a light source.

So my question is what's the difference between using the "sun and sky" which utilises the SunLight and the dome light, vs using SunLight and the environment slot?

SunLight combined with Sky texture in the Environment slot is a default setup to simulate daylight in a simple way and in most cases it can be faster to render.
However, the Adaptive Dome Light is also very efficient especially for interiors, because it automatically recognizes the openings like windows where the actual light is coming from and figures out which portions of the environment to sample and which ones to ignore.

Does enabling Sunlight whilst using domelight (HDRI) as the main source of light make the render run less accurately or does it not matter?

Basically, this is like having two suns in the scene, so if this is not the desired result you will want to disable the SunLight when using the HDRI.

What if i wanted the glass panes to reflect the Sun in certain angles? I know this cant be done with domelight alone.

You can use Dome Light for GI for example and at the same time override Background (in which case in the Dome Light enable invisible) or Reflections (in the Dome Light disable Affect Reflections) in the Environment settings with another texture, if this is needed.
If you need to override properties only of the specific material you can add Override material properties to it.

If the Sun and Sky system is simply a domelight that uses the vray sun, could we just do it manually instead of prompting light gen to do it?

Yes, you can add a Sky texture to the Color/Texture HDR slot in the Dome Light manually.

To sum it up, selecting the workflow depends on the result that is needed and V-Ray provides tools for many case scenarios.