Dome Light Fireflies

[Jim Meston]

I am having a lighting issue getting fireflies where the hotspots are from the dome/portal setup.
I tried just adaptive without the portal but doesn't work as expected, very little light gets in.

Any tips?

[david.anastacio]

Hi Jim Meston, is the light going through glass? If yes, you could try to have the glass ignored or disable the cast shadows on the shader.

Best,
David.

[Jim Meston]

Hi David,

Thanks for your reply.
In this case this isn't the issue. Further investigation leads to the following.

All walls and windows removed.

I have the cam exposure quite high currently so this may have an effect on outcome.

Fist image is linear output, second is with OCIO transform.

To get rid of the fireflies I have to give it 256 samples or something higher.

Not sure if this is just how it is or if there is a solution.

[Jim Meston]

Also worth noting, upping the light subdivs seems to have no effect.

[chakarov]

Hi Jim Meston , could you share the scene, or part of it. My e-mail is georgychakarov@chaosgroup.com

[Jim Meston]

Hi Georgy, stripped scene set by wetransfer.

[chakarov]

Thanks Jim Meston , I've received your e-mail.

[chakarov]

Hi again Jim Meston , this could be caused by some very bright pixel/s in the HDRI, you could ignore those pixel/s by enabing "Clamp Max Ray Intensity" V-Ray ROP > Renderer > Options > Rendering. Seems to work on my side, could you check if it will work for you too.

[Jim Meston]

No this doesn't work for me. I thought that was for secondary rays? In fact this setting seams to do nothing here.

I believe it is to do with the portal light, how it is passing the HDR etc.

[Jim Meston]

Increasing the min shading rate seems to do the trick. So far. Thanks for taking a look !

[chakarov]

That is something I forgot to tell you, you do not need portal lights with V-Ray Next +. Just enable "adaptive dome" option of dome light.

[Joelaff]

While I have not seen the scene you might try blurring your HDRI (in an outside app).

[^Lele^]

What Georgy said: turn on adaptive dome, remove the portals.
The dome has both importance sampling and adaptive shading, it ought to be enough (it is in Max.).
No need to blur the HDRI either, i very frequently use for testing one i made myself with a tiny visible Preetham sun disk (in the millions float), and use no secondary clamping either.

Have enough AA (*not* MSR. avoid touching that!) to reach your chosen noise threshold (which doesn't look like it's the case in your renders), and by the time the sampler is done, you'll be fine.
Use a sampleRate render element (AoV, if you prefer) to figure out if you need more AA sampling to reach the N.T. you set, or not. (Red: bad.).

[Jim Meston]

Thanks guys, the issue I am having is that the portal light is getting loads of light into the scene, and with and adaptive dome light, nowhere near as much light is getting in, i.e. the setup with the portal light (whilst probably light intensity incorrect) was getting close to what was required.
I guess if I just drop the portals and use adaptive I will add some fill lights etc.


[EDIT +info]

Whilst I had spotted and understood the idea of adaptive lights, the reason I wasn't using them apart from stated above, is the on the help card it said WIP, and in the online help it says that they only work with Light Cache GI (I am pretty sure i read that) so I might have led myself down the garden path on this one !

[chakarov]

Your portal Lights has "No Decay" ON, which is adding unlimited light in the scene. That is why the scene is a lot brighter with it. You could remove portals, activate "Adaptive Dome" and set DomeLight multiplier to 3 or 5, or to adjust camera shutter speed in order to lit the scene to the level you want.