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Noise in Delta Keyer Replace Mode

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Matthew Tingblad

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Noise in Delta Keyer Replace Mode

PostThu Mar 26, 2020 3:46 pm

Hi everyone,

I noticed something working with the Delta Keyer in Fusion. Under the matte tab, if I go to "replace mode" and select anything other than "source," I get a lot of extra noise. Presumably this is because Fusion is replacing the greenish bleed over my subject over the green screen.

I made a quick video to compare. The first half is replace mode set to "none," and the second half set to "source." I see more greenish colors in the second half, but it's also a lot less noisy.
https://drive.google.com/file/d/1zE9SXR8k_vu9dOO-0XtiBXNq3ymqc7GF/view?usp=sharing

Is this expected? I'm wondering if there is something I did wrong on my end. Perhaps I used bad lighting (still learning here). If I bought resolve studio, could I do a good job addressing that extra noise in the color page? Or is there something in the delta keyer controls that I am missing?

Thanks for your input!
-Matthew
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Bryan Ray

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Re: Noise in Delta Keyer Replace Mode

PostThu Mar 26, 2020 4:51 pm

It's a common problem with the Color Difference keying method. Keylight does the same thing. I frequently use just the matte from Delta, combining it with the plate in a MatteControl and using MatteControl's own superior spill suppression.

It comes from the max() comparison between channels. Where green is higher than a certain threshold, it gets replaced with the replace color. But noise in the image can push some pixels over the threshold while neighboring pixels keep their color. You can try playing with the Reference color to try to smooth it out, but MatteControl is usually faster and better at suppression.
Bryan Ray
http://www.bryanray.name
http://www.musevfx.com
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Matthew Tingblad

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Re: Noise in Delta Keyer Replace Mode

PostMon Mar 30, 2020 9:36 pm

Thanks. I haven't used MatteControl before. Do you just send the Delta matte to the MattControl Background input, and then mess with the spill controls?

I also noticed that I could pull out some extra green with the color page.
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Bryan Ray

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Re: Noise in Delta Keyer Replace Mode

PostMon Mar 30, 2020 9:47 pm

If you're going to use the RGB output from Delta, yes. What I generally do looks like this:

Code: Select all
{
   Tools = ordered() {
      PipeRouter5 = PipeRouter {
         ViewInfo = PipeRouterInfo { Pos = { 275, 16.5 } },
      },
      DeltaKeyer1 = DeltaKeyer {
         Inputs = {
            BackgroundRed = Input { Value = 0.0797009840607643, },
            BackgroundGreen = Input { Value = 0.0773529857397079, },
            BackgroundBlue = Input { Value = 0.570544302463531, },
            LowThreshold = Input { Value = 0.577, },
            HighThreshold = Input { Value = 0.881, },
            RestoreFringe = Input { Value = 0.00291, },
            TuningRanges = Input {
               Value = ColorCurves {
                  Curves = {
                     {
                        Points = {
                           { 0, 1 },
                           { 0.4, 0.2 },
                           { 0.6, 0 },
                           { 1, 0 }
                        }
                     },
                     {
                        Points = {
                           { 0, 0 },
                           { 0.4, 0 },
                           { 0.6, 0.2 },
                           { 1, 1 }
                        }
                     }
                  }
               },
            },
            AlphaShadowsGain = Input { Value = 1.145, },
            Input = Input {
               SourceOp = "PipeRouter5",
               Source = "Output",
            },
         },
         ViewInfo = OperatorInfo { Pos = { 330, 49.5 } },
      },
      MatteControl1_2 = MatteControl {
         Inputs = {
            ApplyMaskInverted = Input { Value = 1, },
            MatteCombine = Input { Value = 4, },
            Filter = Input { Value = FuID { "Multi-box" }, },
            MatteBlur = Input { Value = 2.48, },
            Passes = Input { Value = 16, },
            LowMatteThreshold = Input { Value = 0.258, },
            High = Input { Value = 0.938, },
            ["Garbage.MaskNest"] = Input { Value = 1, },
            ["Garbage.MaskInverted"] = Input { Value = 1, },
            PostMultiplyImage = Input { Value = 1, },
            SpillSuppression = Input { Value = 1, },
            SpillMethod = Input { Value = 2, },
            Background = Input {
               SourceOp = "PipeRouter5",
               Source = "Output",
            },
            Foreground = Input {
               SourceOp = "DeltaKeyer1",
               Source = "Output",
            },
         },
         ViewInfo = OperatorInfo { Pos = { 550, 16.5 } },
      }
   }
}


The top part of the MatteControl works much like a ChannelBooleans—you can grab a new alpha from the green input. At the bottom, make sure Post Multiply Image is checked to knock out the screen.

This method ensures that I know at a glance exactly what's been done to my RGB. I don't have to open up Delta to check its settings because I know it's only providing a matte. That's a personal compositing philosophy of mine—every step should be a discrete node on the graph to make it as visually clear as possible what's happening.
Bryan Ray
http://www.bryanray.name
http://www.musevfx.com

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