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Fireflies are increasing in renders

seeker273seeker273 Posts: 449
in New Users

The last few days there seems to be a problem with my renders. No matter what change I make in my IRAY settings I get vey bright spots. It's happening in different scenes especially with point lights. The renders range from very bright sunny scenes to very dark. I use hdri's and point lights. I tried all the usual suggestion with max and min samples, render quality etc but no joy :(

The biggest problem is that the fireflies increase the longer it renders. Any suggestions?

Comments

  • glaseyeglaseye Posts: 1,312
    edited June 2017

    I must admit that I've never had any 'firefly-artifacts' in Iray (I remember them from very early Luxrender-versions...)

    Did you check in filtering if the 'firefly filter' is still enabled?

    fireflies.JPG
    470 x 286 - 36K
    Post edited by glaseye on
  • JamesJABJamesJAB Posts: 1,760

    I have a test for you to try.  Set up a simple scene that will render quickly.  Hit render and verify that your firefly problem is happening during the render.

    Go into your render settings and change your Iray device to CPU only.  Hit render again and check to see if your firefly problem is still happening (The CPU render will take longer, that is why I suggested a simple scene)
    Next do the same with only the GPU selected for Iray rendering and check for the firefly problem.

    At this point if the firefly problem happens during the GPU rendering and not the CPU rendering, your video card may be going bad. (most likely one of the Vram chips on the card overheated and became damaged)

    If there are no firefly artifacts in either render then make the scene more complex and go through the steps again.

    I am not sure how a Vram issue would manifest itself in Windows 7-10 but back in the day (Windows XP) I had a card with a bad Vram chip and when scrolling up and down web pages with dark backgrounds it would draw extra light colored dots in vertical patterns up and down the page.  Depending on how severe the issue is it may only manifest itself when the card is under load.

    Enjoy troubleshooting 101 (Hopefully it's not the GPU and is some setting that you changed and forgot about)

  • ToborTobor Posts: 2,300

    Whenever this is a change to rendering that wasn't there before, especially if rendering the same (or same kind of) scenes, start here:

    1. Reboot your computer. 

    2. Check for any stealth updates of your video card driver, if you're using GPU rendering (in whole, or part).

    3. Be sure the Firefly filter wasn't accidentially turned off.

    Fireflies are caused by inbalances in the shaders, particularly those that use absolute white for any color, or those that create a lot of specular highlights. The type of lighting can have a bearing, as lights with a high specular content -- better HDRIs and point lights where the emitter is a point or very small -- will compound the issue. Futzing with max/min pixels etc. only covers that up. Extending the render time will usually resolve the fireflies, because that's how Iray works, but it's best to avoid them as much as you can in the first place.

  • seeker273seeker273 Posts: 449
    edited June 2017

    Thanks guys. Unfortunately I don't have NVidia so it's CPU only for me. Fortunately it was the Firefly filter having been turned off that caused the problem. I still don't know how that happened since I never ventured in that particular tab before. But all is well that ends well :)

    Thank you :)

    Post edited by seeker273 on
  • InkuboInkubo Posts: 745

    Seeker, I know your problem is solved, but I want to leave a comment here that might help others. I made a Star Wars themed scene using my recent most favorite character, Lekkulion, with a New Colony set and one of the PC+ robots. I used image-based lighting (one of the skies from TerraDome 3), but turned down the environment intensity in the render to simulate twilight. I didn't want a bright scene because I made some surfaces on the robot and Lekkulion's irisis all glowy. And finally I applied shiny Iray metallic surfaces to the robot.

    When I rendered that scene, there were fireflies everywhere! Everywhere! JamesJAB's post above kinda scared me... was my brand-new video card failing? But then I added one Distant Light to the scene, and just with that single change, the fireflies went away. I didn't even have to increase the Distant Light's luminosity above its very dim default--simply having a light besides the dome's IBL banished all the fireflies.

  • seeker273seeker273 Posts: 449
    Inkubo said:

    Seeker, I know your problem is solved, but I want to leave a comment here that might help others. I made a Star Wars themed scene using my recent most favorite character, Lekkulion, with a New Colony set and one of the PC+ robots. I used image-based lighting (one of the skies from TerraDome 3), but turned down the environment intensity in the render to simulate twilight. I didn't want a bright scene because I made some surfaces on the robot and Lekkulion's irisis all glowy. And finally I applied shiny Iray metallic surfaces to the robot.

    When I rendered that scene, there were fireflies everywhere! Everywhere! JamesJAB's post above kinda scared me... was my brand-new video card failing? But then I added one Distant Light to the scene, and just with that single change, the fireflies went away. I didn't even have to increase the Distant Light's luminosity above its very dim default--simply having a light besides the dome's IBL banished all the fireflies.

    Great tip Inkubo!

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