Expression to change a value in frame intervals

HI!

i'm sure this must have been asked before but i searched and could not find anything about it. i might not be using the correct terms as i am very new to resolve/fusion and video editing in general.

what i want to be able to do is basically make neon light turn on for x amount of frames then turn off for x amount and repeat. i know i can do this by manually key framing the merge blend, and copy and pasting in the splines page can speed that up as well, but, i thought maybe an expression could speed things up.

like something about time changing the blend to number value 1 then switch to number value 2 after the right amount of frames then it goes back to num 1 etc. any help to this newbie would be much appreciated!

Try setting Blend to 'Modify With > Perturb' ... page 211 in the DaVinci-Resolve-17-Fusion-Visual-Effects.pdf

You can also use an expression with a modulo component, but my math is terrible, so I don't know how that works. In the spline editor you can also set up you keyframes once and then instead of copy/pasting just set the spline to loop. This way you only have to adjust two to three keyframes and it will ripple through your whole animation.

Here's an example expression using the modulo method as Sander explained:

Code: Select all

iif(time % 10 == 0, 1, 0)

That will set the field to 1 if the current frame number is divisible exactly by 10 (including frame 0), and 0 if it's not.

So if this expression was added to a Merge Blend field, the merge foreground will display on frames 0, 10, 20, 30, etc, and not on any of the others. Change the '10' in the expression to display after a different number of frames.

Here's a trivial example composition demonstrating that:

Code: Select all

{
   Tools = ordered() {
      Merge1 = Merge {
         CtrlWZoom = false,
         Inputs = {
            Blend = Input { Expression = "iif(time % 10 == 0, 1, 0)", },
            Background = Input {
               SourceOp = "Background1",
               Source = "Output",
            },
            Foreground = Input {
               SourceOp = "Text1",
               Source = "Output",
            },
            PerformDepthMerge = Input { Value = 0, },
         },
         ViewInfo = OperatorInfo { Pos = { 1252.67, 212.212 } },
      },
      Background1 = Background {
         Inputs = {
            Width = Input { Value = 1920, },
            Height = Input { Value = 1080, },
            ["Gamut.SLogVersion"] = Input { Value = FuID { "SLog2" }, },
         },
         ViewInfo = OperatorInfo { Pos = { 1142.67, 212.212 } },
      },
      Text1 = TextPlus {
         Inputs = {
            Width = Input { Value = 1920, },
            Height = Input { Value = 1080, },
            ["Gamut.SLogVersion"] = Input { Value = FuID { "SLog2" }, },
            StyledText = Input { Value = "Example", },
            Font = Input { Value = "Open Sans", },
            Style = Input { Value = "Bold", },
            VerticalJustificationNew = Input { Value = 3, },
            HorizontalJustificationNew = Input { Value = 3, },
            ManualFontKerningPlacement = Input {
               Value = StyledText {
                  Array = {
                  },
                  Value = ""
               },
            },
         },
         ViewInfo = OperatorInfo { Pos = { 1210, 129.182 } },
      }
   }
}

Try setting Blend to 'Modify With > Perturb' ... page 211 in the DaVinci-Resolve-17-Fusion-Visual-Effects.pdf

that will make it a random value giving it a more candle/flame like effect. i want it to switch on and off at set intervals like in the case i was working on going from .25 blend on the merge from fram 0-19 then immediately switch to 1 at frame 20 and and hold there till 39 then back to .25, and repeat. unless there is a way to control the perturb i haven't learned!

You can also use an expression with a modulo component, but my math is terrible, so I don't know how that works. In the spline editor you can also set up you keyframes once and then instead of copy/pasting just set the spline to loop. This way you only have to adjust two to three keyframes and it will ripple through your whole animation.

you can do that O.o. i will try it! that would do it!

Here's an example expression using the modulo method as Sander explained:

Code: Select all

iif(time % 10 == 0, 1, 0)

That will set the field to 1 if the current frame number is divisible exactly by 10 (including frame 0), and 0 if it's not.

So if this expression was added to a Merge Blend field, the merge foreground will display on frames 0, 10, 20, 30, etc, and not on any of the others. Change the '10' in the expression to display after a different number of frames.

Here's a trivial example composition demonstrating that:

Code: Select all

{
   Tools = ordered() {
      Merge1 = Merge {
         CtrlWZoom = false,
         Inputs = {
            Blend = Input { Expression = "iif(time % 10 == 0, 1, 0)", },
            Background = Input {
               SourceOp = "Background1",
               Source = "Output",
            },
            Foreground = Input {
               SourceOp = "Text1",
               Source = "Output",
            },
            PerformDepthMerge = Input { Value = 0, },
         },
         ViewInfo = OperatorInfo { Pos = { 1252.67, 212.212 } },
      },
      Background1 = Background {
         Inputs = {
            Width = Input { Value = 1920, },
            Height = Input { Value = 1080, },
            ["Gamut.SLogVersion"] = Input { Value = FuID { "SLog2" }, },
         },
         ViewInfo = OperatorInfo { Pos = { 1142.67, 212.212 } },
      },
      Text1 = TextPlus {
         Inputs = {
            Width = Input { Value = 1920, },
            Height = Input { Value = 1080, },
            ["Gamut.SLogVersion"] = Input { Value = FuID { "SLog2" }, },
            StyledText = Input { Value = "Example", },
            Font = Input { Value = "Open Sans", },
            Style = Input { Value = "Bold", },
            VerticalJustificationNew = Input { Value = 3, },
            HorizontalJustificationNew = Input { Value = 3, },
            ManualFontKerningPlacement = Input {
               Value = StyledText {
                  Array = {
                  },
                  Value = ""
               },
            },
         },
         ViewInfo = OperatorInfo { Pos = { 1210, 129.182 } },
      }
   }
}

i knew this had to exist! thank you so much!