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Matching sky motion with tracker

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Steve Iskenderian

  • Posts: 53
  • Joined: Mon Apr 13, 2015 6:54 am

Matching sky motion with tracker

PostMon Apr 17, 2017 1:02 pm

I have a hard time doing such a simple comp.


1. I have a footage where the camera pans 120 degrees or so.

2. I want to add a sky in the background (still image bigger than the footage so it covers the frame all the time).

3. I add a tracker and track the footage successfully.

4. I add a transform node on the sky image, connect its center to tracker path position.

5. There is motion discrepancy between the FG and the sky. There is parallax and the sky seems to be "sliding'.

Despite the fact that this is the worflow for this, it seems to be missing a parameter.
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Bryan Ray

  • Posts: 74
  • Joined: Mon Nov 28, 2016 5:32 am

Re: Matching sky motion with tracker

PostMon Apr 17, 2017 6:11 pm

This is just a guess based on your description.

Your sky footage needs to be the same resolution as the footage you originally tracked because Fusion's transforms operate on a percentage of image basis, not on a pixels basis. If you Merge the sky over a Background with the same resolution as your tracked plate before your Transform, it should do what you expect.

I do this so often that I made a macro:

Code: Select all
{
   Tools = ordered() {
      Reformat = MacroOperator {
         CtrlWZoom = false,
         Inputs = ordered() {
            Input1 = InstanceInput {
               SourceOp = "Background5",
               Source = "Width",
               Default = 1920,
            },
            Input2 = InstanceInput {
               SourceOp = "Background5",
               Source = "Height",
               Default = 1080,
            },
            Input3 = InstanceInput {
               SourceOp = "Background5",
               Source = "Depth",
               Default = 0,
            },
            MainInput1 = InstanceInput {
               SourceOp = "Merge13",
               Source = "Foreground",
               Name = "Input",
            },
         },
         Outputs = {
            MainOutput1 = InstanceOutput {
               SourceOp = "Merge13",
               Source = "Output",
            },
         },
         ViewInfo = GroupInfo { Pos = { 495, 247.5, }, },
         Tools = ordered() {
            Background5 = Background {
               CtrlWZoom = false,
               CtrlWShown = false,
               Inputs = {
                  GlobalIn = Input { Value = 1, },
                  GlobalOut = Input { Value = 74, },
                  Width = Input { Value = 1920, },
                  Height = Input { Value = 1080, },
                  ["Gamut.SLogVersion"] = Input { Value = FuID { "SLog2", }, },
                  TopLeftAlpha = Input { Value = 0, },
                  Gradient = Input {
                     Value = Gradient {
                        Colors = {
                           [0] = { 0, 0, 0, 1, },
                           [1] = { 1, 1, 1, 1, },
                        },
                     },
                  },
               },
               ViewInfo = OperatorInfo { Pos = { -55, 10.15, }, },
            },
            Merge13 = Merge {
               CtrlWZoom = false,
               CtrlWShown = false,
               Inputs = {
                  Background = Input {
                     SourceOp = "Background5",
                     Source = "Output",
                  },
                  PerformDepthMerge = Input { Value = 0, },
               },
               ViewInfo = OperatorInfo { Pos = { 55, 10.15, }, },
            },
         },
      },
   },
   ActiveTool = "Reformat",
}
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Sander de Regt

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  • Joined: Thu Nov 13, 2014 10:09 pm

Re: Matching sky motion with tracker

PostMon Apr 17, 2017 8:28 pm

Steve, Bryan is partially right. Depending on your workflow this might be the solution you're looking for, but...

The great thing about Fusion is it's resolution independence. It's hardly ever necessary to match resolutions at all. Merges and Transforms even concatenate, meaning that you can merge an HD image on top of another HD image with a size of 0.01 and then put a transform tool after that, set the size to 100 so the merged image will fill the screen again and you will have NO quality loss on the resulting image.

If you do your sky merge straight in the tracker it will sort out the sizes all by itself, so you can merge a 16K image on top of an SD frame and everything will match up fine. You do have to put a transform between the 16K loader and the tracker tool, but apart from that there are no problems with this setup.
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Steve Iskenderian

  • Posts: 53
  • Joined: Mon Apr 13, 2015 6:54 am

Re: Matching sky motion with tracker

PostTue Apr 18, 2017 3:10 pm

Thank you very mcuh guys, I really begin to understand the logic of it. Makes a lot sense actually.

ps: it is not the same I asked in a previous post (the other one was for a 3d merge, which resembles to this actually). So people won't think their advises were in vain, they were indeed much useful.

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