No idea why there is so much noise/fireflies

[sburkeW2VGV]

Hey guys. I never had this problem with exterior scenes before. In this scene, I didnt do anything different from what i usually do. I have an HDRI map for ligthing, and a small corona light in spherical shape added in the garage. The window frames and roof is made out of PVC plastic matte material. I tried various materials (including a regular corona material) on the window frames.. I tried turning off glossiness and reflection on all the materials. I just cant get those firelies away from the render. As you can see, there is also fireflies in the grass and slightly in the bushes and trees also. Its so annoying! Any idea what i am doing wrong?

 

[darawork · Accepted solution]

Hi,

The number one cause for fireflies in Corona is due to ramping up the light multipliers in the lightmix section of the Virtual frame Buffer render window. All light values should not go above 1.0
The process should be; create your desired lightmix by changing the values in real-time, then once you're happy with the balance press the  '>scene' button, stop the render and then restart the render again. This bakes the light multiplier values into the actual lights themselves and does not rely on the VFB to multiply the lights artificially. When you boost the light values over 1.0 in the VFB you are also boosting the noise that needs to be resolved. You can safely boost all you want, but just remember to press the ">scene" button after you're happy with the look of the scene, then stop, and re-start the render for the changes to take effect.

"The bake lightmix to scene button".

Another thing to check is that you are not using any CoronaMTL materials to light the scene, or emissive values in regular CoronaLegacy Materials or the new Physical material.
You should also add an Albedo render element and check if anything appears red in the render element drop down. The red areas are materials with out-of-range white values and will contribute to added noise and fireflies.
Another thing to check is that you don't have any light sources inside glass, or other transparent materials. The light source should always be outside, as close as possible to trick the viewer that the light is emanating from the inside, but it's actually just outside the object.. e.g light emitters inside a glass bulb etc...

Also, because yours is an outdoor scene, I would make sure that the Primary and Secondary solvers, in the Performance tab of the main render setup window are both set to 'Path Tracing'. 'UHD' Cache is mainly used for indoor scenes.


This is a very handy tutorial to watch so as to avoid some common mistakes:

Let me know how you get on, or if any of the above helps. 
Regards 🙂

[sburkeW2VGV]

I solved the problem. I did what you said. I turned everything to 1.0 value. I used the EV for more brightness instead. I also adjusted the gamma back to 1.0, in the Color Correction I had attached to the HDRI. I think the decrease of gamma value was totally causing those fireflies. Now there is almost nothing. Thanks for the response!

[darawork]

Sweet. Glad to be of help. I noticed my renders improving and taking less time to render just by keeping everything 1.0 or less in the VFB too. It's probably the most important thing to remember.

Regards,

[sburkeW2VGV]

I will definately remember that. Its so easy to get lazy and hung up with the luxery of the lightmixing. Cheers!