I’m currently rendering some pathtracer scenes and am disabling Unreal’s tone curve in the render settings to get maximum quality for color. However, disabling the tone curve or having the ocio config enabled gives me a ton of hot pixels / fireflies in the bright reflection areas.
Is there any console variable I can add or method of getting rid of this in Unreal?
I’ve tried every noise reduction, dust and scratches, dust buster effect outside of Unreal in Davinci and After effects but none seem to work without ruining the image.
I am trying to sort the same issue. Running UE 5.3.2
I have tried increasing samples on everything I can find.
PostProc:
RayTracedGlobalI llum 32
Ray Tracing Reflections 16
Path Tracing Samples Per Pixel 512
Path Tracing Max Bounces 4
Denoiser is OFF - cannot use that for VFX production
Bloom OFF
Lens Flares OFF
Vignette OFF
Max Path Exposure 3
Exposure Min EV100 0.0 Max EV100 0.0 (so the color/values are not adjusted by UE)
My Light is just a dome light with an HDRI and the sun is clamped to 3 so not crazy high values there either. ANd I have a directional light value 1.9
LOTS of fireflies, all that stuff did nothing.
I tried putting an area light 20,000 units away and up in the sky and made it 40,000 cd bright with attenuation at 100,000, to match the illumination given by the dir light and … the fireflies are back.
Hmmmm…
Any suggestions on the settings on the lights that might be causing this?
it was likely solved by having a less shiny material (0.15 roughness and above).
I’ve came across this in the worst possible way on shiny surfaces with hundreds of fireflies with no way of getting rid of them no matter what AA settings i’ve used in the movie render queue (the editor view’s path tracer had no problem with it at all for a single frame screenshot) but when ive read it somewhere that some renderers have issues with values close to 0 ive realised that is what is likely causing it, tried it and yep, that was it (well… most of it).
After experimenting with a scene that had a ton of it I can say with certainty that it can be caused by a lot of things and if you are in that situation you have to try all of the below and maybe go backwards and find whats causing yours (outdoor scene):
remove all post processing effects that could cause it: no sharpness, no bloom, no chromatic aberration, no high contrast from pp effects
put a base material on everything with mid values (0.5 for everything except metallic zero) and see if its all gone, this is just for ruling out if its a lighting issue or material issue (or both)
if there are still a ton of it what might sound stupid but it actually made my scene way worse as I was already using real world values and tried the default “10” for the sun and got 10x more white pixels - set the sun light to 100k, sky light above 1 maybe to 3 (if its a hdr wrapped skylight - 20k int for the image), and adjust the post processing volume exposure to get a similar visual result to your original scene setup. real world values seem to work better for path tracer.
if the white pixels appear along edges of certain objects it is very likely some material setting that causes most of it. I’ve set everything between 0.1 an 0.9 and got rid of at least half of the white pixels
path tracer does not like high frequency textures either so a busy normal map or any other map can also cause problems
what I can’t fully grasp yet is white pixels where two different materials meet with all of the above already removed about 85% of the fireflies I still could not get rid of these yet. sometimes even on one material where shadow and light meets. could be a shadow type problem.
The look of the scene will definitely change slightly, wont be able to get a perfect match to the original, but you can always adjust it in post to try to match it better with the rest of the footage if needed.
What I’ve also seen in my case is that there are a lot more hot pixels in areas where the camera is not focusing (turned off DOF to see the scene better) → A slight DOF will hide most of it, which is actually not a bad idea as most cameras will have at least a minimal dof in most cases (if its not a still scene shot from a tripod with long exposure)
in the end ive managed to remove around 95-98 percent of the white pixels by also increasing the overall brightness of the scene a bit with post processing. no idea why that helped as it was already well lit.
