Grainy Render suggestions

I've watched all sorts of tutorials about grainy render problems and have tried them all, but I'm still having trouble reducing the graininess in the background of this image.  I have render quality set at 5 with a 98% level.  There are seveal ghost lights in front, above and behind the two main figures as well as the visible lights in the background.  I've set the exposure to several values, this one set at 8.5 and my ISO is at 100.  (I tried it higher, but it didn't seem to help.  It got lighter, but the graininess didn't go away.)

Any suggestions?

GrainyProblem.jpg
1250 x 938 - 235K

Comments

  • PerttiAPerttiA Posts: 9,744

    Set "Rendering Quality Enable" off and let it run as long as it takes to get rid of it.

    Are you rendering on GPU or CPU?

  • felisfelis Posts: 3,851

    I looks to me as there is too little light in the room.

    Not a strong light, but a large light. You could try setting the ceiling to emissive with a fairly low value, or create a plane and scale it up to nearly the size of the ceiling.

    Exposure and ISO will not give more light, just change the overall tonemapping.

  • teechurz_7c41d96282 said:

    I've watched all sorts of tutorials about grainy render problems and have tried them all, but I'm still having trouble reducing the graininess in the background of this image.  I have render quality set at 5 with a 98% level. 

    That doesn't affect how good the render is at a given time, it affects how fussy Iray is about calling it done (Render Quality sets a threshold for considering a pixel converged, the Render converged percent sets how many have to reach that to call the render done). The render will still stop if it exceeds the maximum number of samples or time.

    There are seveal ghost lights in front, above and behind the two main figures as well as the visible lights in the background. 

    Done forget that light, other than distant lights, falls off with the inverse square law - so your ghost lights probably aren't helping that much (and how much theya re contributing will depend how recent your version of iray, and so DS, is and how you are making them - "old-style ghost lights in recent versions of DS do not do much).

    I've set the exposure to several values, this one set at 8.5 and my ISO is at 100.  (I tried it higher, but it didn't seem to help.  It got lighter, but the graininess didn't go away.)

    Tone mapping makes little different to noise. That sounds like there is quite a lot of light, at least near to, but the main determinant of convergence speed is how widely spread the lights are 9which is the point of ghost lights) - if light has to do a lot of bouncing to reach soem areas then fewer paths will hit them and so they will take proportionately longer to converge. How much light bounces is also an issue - if there are a lot of reflective surfaces for a light path to bounce off without significant dimming then it will take a lot longer to reach a final value then if many surfaces were non-reflective, so that paths hitting them tended to stop. Of course not enough bounces would make it even harder for light to reach more awkward areas.

    Any suggestions?

  • It was the ghost lights I was using.  I had a couple of panels across the ceiling I was using, but they just weren't doing the trick.  I added a couple of different ones from a different vendor and they brightened it up just right without going overboard.

    Thanks for the help!

  • crosswindcrosswind Posts: 5,121
    edited February 2023

    teechurz_7c41d96282 said:

    It was the ghost lights I was using.  I had a couple of panels across the ceiling I was using, but they just weren't doing the trick.  I added a couple of different ones from a different vendor and they brightened it up just right without going overboard.

    Thanks for the help!

    'Old Ghost Light' might bring you 'grainy / blurry' result in some cases. esp. when they're in front of your cameras... Try this: https://www.daz3d.com/forums/discussion/609556/creating-a-ghost-light-daz-studio-4-21-1-25

    I found things changed a lot after using this ' new one'...

    Post edited by crosswind on
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