Hi guys,

So I've been reworking an older project and part of that was relighting. My set up is:

interior set lights: (light linked to not light any objects outside, including glass, except sunlight)
skylight with hdri, portal geo that spans the glass windows
sunlight
two sun bounces (area lights)

exterior set lights: (light linked to affect only glass, outside vegetation)
skylight with same hdri, but no portal geo
sun bounce (area light)

Render settings:
6x6 samples
5 min ray
13 max ray
diffuse quality 3
reflection quality 3
refraction quality 3
diffuse limit 1

I having a massive issue with these huge fireflies. Any ideas what the issue is?

When I get back to the computer tomorrow I'll re-add the lights in the render one by one to fish out the problem, but I was wondering if anyone else ran into this issue. I think its with the portal geo?? Thats the only thing I havent used before and I havent had this issue before now.

I have a render attached. The black object is a matte.

Thanks guys!

Try limiting light intensity/exposure, clamp the HDRI map and avoid using GGX specular in shaders.

Or use a 3rd party renderer better suited to interiors.

thanks for the reply @cpb

So it is the portal geometry that is giving me the noise. I turned off every light and then turned that one back on (checked the other as well). I turned the intensity down to one and still received the same amount of noise. I upped the sampling quality and glossy filter amount of the light and no change.

I then just turned off the portal geo and the noise went away. I tested it further and used a classic shader with the specular model set to blinn, still received noise. I went back to the light. I removed the hdri completely and the noise went away but I still had the portal geo on.

For this project I am required to use mantra unfortunately.

How do I clamp the hdri? I think that is what's going to fix my problem. I did another test with an hdri of a medium dynamic range and it eliminated the fireflies.
This is the HDRI I'm using which as an extremely high dynamic range: https://hdrihaven.com/hdri/?h=derelict_overpass [hdrihaven.com]

I suppose there are some limitations of which hdris can be used. Worst case scenario I'll find a different hdri.

clamp with limit COP, save as rat or pic.