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T
teamopenbook
Participant
June 19, 2018
Answered

Displacement Map artifacts

  • June 19, 2018
  • 1 reply
  • 2355 views

Hello!

Long (ish) time After Effects user, but learning more every day! I have had lots of help from this forum over the years, and recognize some of the consistent members around here. Its a strong and helpful community!

Anyway, I have recently come across an issue that I can't figure out. I wont bother with an intimate explanation of how I built this, but its relatively strait forward. Using a pre comp with 5 animated shape layers to drive a displacement map (disp map effect placed on an adjustment layer) which distorts/deconstructs a pair of images.

Pre comp driving displacement map: (these shapes are just animating scale larger and smaller)

Pre-comp with image: (only needed to pre comp so I could have the 2 color bars on the side)

Main composition: (this looks and works exactly how I want it to, EXCEPT for the hair/glitch/artifacts that are present

Artifacts circled in red here:

Things I have tried:

-Render in .mov with a Alpha channel

-Render in mp4 from AME

-restart computer and AE

-many blending modes

-different images

Its important to note that the different images do not have an effect on the artifacts – which tells me the issue is somewhere in the displacement map? It could be that I am not fully educated on how to us this effect, or am using it improperly.

If relevant:

Sorry for the long-winded post, but I wanted to give as much info as possible to save time on everyones end.

I really appreciate everyone's time in making this community helpful and useful!

      This topic has been closed for replies.
      Correct answer pconigs

      If I had to guess, I'd say it has to do with soft sub-pixel edges in those shape layers. Say you have a rectangle that's 100 pixels wide, but it's position is at 900.5 pixels, that gives you a slightly darker pixel on each edge, but not black. Then the displacement map is set to move anything full red right 200 pixels. The majority of the image is moved that full 200 pixels, but since the edge of the rectangle sites on a half pixel, a tiny part of the image is only moved 100 pixels.

      If this is the cause, and since you're animating scale, an easy fix might be to put a Threshold effect in an adjustment layer above your shape layers, and place a black solid at the bottom. This will get rid of any alpha in your precomp, and get rid of any sub pixel edges.

      1 reply

      pconigs
      pconigsCorrect answer
      Participating Frequently
      June 19, 2018

      If I had to guess, I'd say it has to do with soft sub-pixel edges in those shape layers. Say you have a rectangle that's 100 pixels wide, but it's position is at 900.5 pixels, that gives you a slightly darker pixel on each edge, but not black. Then the displacement map is set to move anything full red right 200 pixels. The majority of the image is moved that full 200 pixels, but since the edge of the rectangle sites on a half pixel, a tiny part of the image is only moved 100 pixels.

      If this is the cause, and since you're animating scale, an easy fix might be to put a Threshold effect in an adjustment layer above your shape layers, and place a black solid at the bottom. This will get rid of any alpha in your precomp, and get rid of any sub pixel edges.

        T
        teamopenbookAuthor
        Participant
        June 19, 2018

        Perfect! That was exactly it. Once you said it, that made perfect sense.

        To clarify, here's exactly what I did:

        Added adjustment layer and CC Threshold to that layer. Had to make sure the channel was set to Alpha, and definitely had to play with the exact number for Threshold. Also for whatever reason it had to be CC Threshold, not Threshold. (it could be that I wasnt using it right). Finally, I didn't end up needing the black solid. Seems like CC Threshold added some render time though. Not a big deal though!

        You saved me a lot of time. Thanks so much for taking the time to help!

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