Answers.Body: <p>Assuming you're using a layer based compositor (like After Effects) you need two layers. The top layer has the half-painted box with the hand swiping over it. The bottom has the fully painted box, and no hand, but everything else is the same as the first shot.</p>
  
  <p>Now you need to make a matte that corresponds to the trailing edge of the hand, and extending (roughly) to the the top left of the screen and down the left side. As the hand moves across this matte will follow it, so that at the start it is not over the box, and at the end it completly covers it. the easiest way to do this would be to trace the hand, but there are other ways like rotobrush in After Effects. Apply this matte to the top layer so that it hides everything inside it.</p>
  
  <p>Alternatively you could shoot the hand over a green background and use chroma keying to remove the background. Then use a simple matte to reveal the painted box, with the transition hidden by the hand layer. You could even get away with a single still image of the hand, animated to look like it was moving, if the movement is fast and simple enough.</p>
  
  <p>It's certainly doable with After Effects, but You could use Blender or any compositor or NLE that has the capability to create moving mattes</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-03-23T10:31:05.230Z
Answers.Text: So the key element is the matte thing, right? I am just a newbie in video editing btw
Answers.UserDisplayName: im_chc
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-03-23T10:37:04.573Z
Answers.Text: Also, is it doable in Natron ?
Answers.UserDisplayName: im_chc
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-03-23T22:37:10.557Z
Answers.Text: Sorry, I don't know enough about Natron to say.
Answers.UserDisplayName: stib
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-03-23T08:21:52.277Z
Answers.LastActivityDate: 2018-03-23T08:21:52.277Z
Answers.UserDisplayName: stib
Body: <p>How to achieve the "magic swipe" effect in this video (at 0:16)?</p>
  
  <p><a href="https://www.facebook.com/diplycrafty/videos/1867777256617888/" rel="nofollow noreferrer">https://www.facebook.com/diplycrafty/videos/1867777256617888/</a></p>
  
  <p>Is it necessary to use After Effects? Can other open source software do so too?</p>
  
Tags: <after-effects><special-effects>
Title: How to achieve the "magic swipe" effect in this video?
UserDisplayName: im_chc
ThreadText: # How to achieve the "magic swipe" effect in this video?
  
  (Asked by: username_0 on 2018-03-23)
  
  How to achieve the "magic swipe" effect in this video (at 0:16)?
  
  <https://www.facebook.com/diplycrafty/videos/1867777256617888/>
  
  Is it necessary to use After Effects? Can other open source software do so too?
  
  **Tags:** after-effects, special-effects
  
  
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  ## 1 answers
  
  ### Answer by username_1 on 2018-03-23. Score: 3 | Accepted answer
  
  Assuming you're using a layer based compositor (like After Effects) you need two layers. The top layer has the half-painted box with the hand swiping over it. The bottom has the fully painted box, and no hand, but everything else is the same as the first shot.
  
  Now you need to make a matte that corresponds to the trailing edge of the hand, and extending (roughly) to the the top left of the screen and down the left side. As the hand moves across this matte will follow it, so that at the start it is not over the box, and at the end it completly covers it. the easiest way to do this would be to trace the hand, but there are other ways like rotobrush in After Effects. Apply this matte to the top layer so that it hides everything inside it.
  
  Alternatively you could shoot the hand over a green background and use chroma keying to remove the background. Then use a simple matte to reveal the painted box, with the transition hidden by the hand layer. You could even get away with a single still image of the hand, animated to look like it was moving, if the movement is fast and simple enough.
  
  It's certainly doable with After Effects, but You could use Blender or any compositor or NLE that has the capability to create moving mattes
  
  > **Comments:**
  > **username_0**: So the key element is the matte thing, right? I am just a newbie in video editing btw  
  > **username_0**: Also, is it doable in Natron ?  
  > **username_1**: Sorry, I don't know enough about Natron to say.  
  
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