Vray Dome light noise?

[sassom]

Hello everyone,

I'd like to light an interior scene with HDRI dome light. It creates a lot of noise (small white dots actually), unless I pump up the subdivisions or the dome light, or the DMC image sampling, but that increases the render time too much. I've got to make an animation quickly, so the time is really crucial. (The noise is not created by the HDRI, but the dome light itself- it also exists if I apply no map to the dome light.)

I'd like to achieve an optimal solution. What's the best solution to get rid of that noise?

An alaternative method I've been trying: I found out that if I don't use dome light, instead apply the HDRI map in the VRay Environment override slot, it creates no noise, but the GI quality is much lower than with the dome light, the shadows blur out too much (I'm using irrmap+light cache by the way). It only improves, if I render with high irradiance map settings, but it's still much worse quality than with dome light. If I use Brute force+light cache, the shadows improve, but it's noisy, and takes forever to render.

So: what's an optimal solution? I'd like to have acceptable quality shadows with low noise, and quick render times.

Thanks in advance!

sassom

[Svetlozar Draganov]

DomeLight in general produce more noise than other Vray-lights since it emits light from a lot lights arranged spherically/hemispherically around the scene.
There are two ways to decrease the noise-levels - the first one is to increase subdivisions which as you've already notices also increase render-time, and the second one is to check Store With Irradiance Map option and Vray will calculate DomeLight illumination using Irradiance Map engine. For the second approach it is necessary to turn on Irradiance Map GI otherwise the result won't be accurate.

Another option would be to place HDRI texture into Background Slot and place VrayLights behind the windows.

[sassom]

Thank you for your answer!
This helped me a lot.

I see, the "Store with Irradiance Map" option produces kind of similar result as inserting the HDRI map into the Vray Environment override slot (or the background slot, as you said).

So if I see it right, this way the shadows' quality can be adjusted by Irradiance map settings?

Thanks again!

[tashko.zashev]

Thank you for your answer!
So if I see it right, this way the shadows' quality can be adjusted by Irradiance map settings?

Yes, for this setup higher Irradiance subdivisions settings are recommended if you need more sharp and detailed shadows.

Also you may have noticed that the V-Ray Dome light has and advanced option (MIS)

this option allows to disable Multiple Importance Sampling for the light. When MIS is enabled (the default), the light's contribution is split between direct illumination on the one hand, and GI (for diffuse materials) or reflections (for glossy surfaces).

It is ON by default and the noise level is being reduced a lot when using GI (Irradiance map mode for an example).