Swishy transparency

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Jkoseattle
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Swishy transparency

Post by Jkoseattle » Fri Feb 07, 2020 3:52 pm

I have a brief movie with a figure moving across the screen very quickly. Motion blur is making it look great. Now I need to insert this little movie in a bunch of different projects, and have its background transparent so that I can see the scene behind it.

I tried setting the background to green in this little movie and then inserting it into my video editor, setting the transparent color to the green. It works ok, but with all that motion blur a lot of greenish hues still come through on the edges of the image. I think there's a way in Moho to set a transparent color on a movie I import into another project, but I suspect it would present the same problem, since the motion blur makes parts of the image semi-transparent and so the green changes enough to no longer be transparent.

How can I solve this?
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slowtiger
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Re: Swishy transparency

Post by slowtiger » Fri Feb 07, 2020 5:00 pm

Best way is to create this in any pixel-based program on real transparency - Photoshop, Gimp, TVPaint.
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Jkoseattle
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Re: Swishy transparency

Post by Jkoseattle » Fri Feb 07, 2020 5:16 pm

Ah ok, you mean instead of using Moho's motion blur?
Most of the time I'm doing music stuff. Check me out at http://www.jimofseattle.com/music.

Thing I did for work: https://www.youtube.com/watch?v=LgFYGqifLYw
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slowtiger
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Re: Swishy transparency

Post by slowtiger » Fri Feb 07, 2020 5:22 pm

If you're happy with that, use it. Just export without any background, in a format which supports alpha channel/transparency.
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Jkoseattle
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Re: Swishy transparency

Post by Jkoseattle » Fri Feb 07, 2020 5:50 pm

I don't understand that, when I go to Project Settings, there's no ability to set the alpha channel/transparency for the background. How do I export with no background?
Most of the time I'm doing music stuff. Check me out at http://www.jimofseattle.com/music.

Thing I did for work: https://www.youtube.com/watch?v=LgFYGqifLYw
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alanthebox
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Re: Swishy transparency

Post by alanthebox » Fri Feb 07, 2020 6:19 pm

As long as there's no background layer art, you should just be able to go to File/Export Animation, and change the format to Image Sequence. PNG seems to be the preferred format for exporting with alpha.
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Greenlaw
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Re: Swishy transparency

Post by Greenlaw » Fri Feb 07, 2020 11:07 pm

I agree with alanthebox: just render out a PNG image sequence. In Moho, if the background is disabled, Moho will automatically render the image with a transparent background. Then you can use another program to compile the sequence as a movie file that properly supports alpha channel. I typically use a compositing or editing program for this, but some movie players can also do this.

For motion blur, I never render the effect directly from an animation program, 2D or 3D. I find it's better use a compositing program to add the effect in post. In After Effects, for example, the native Pixel Motion Blur effect does a nice job. If you look at the animated titles I created for Hearts Like Fists a few years ago, that's how I added the motion blur effect there. Adding the blur effect in post probably saved me hours of Moho render time, especially since I needed to render many of the Moho scenes multiple times before I was finished.

If Moho supported exporting a motion vector pass, preferably embedded as a channel in an .exr file, a plugin like RSMB Pro in AE could read that data for a more accurate motion blur effect with fewer artifacts. Adding motion blur this way is faster and it looks better too. Other compositing packages, like Fusion and Nuke, have native optical-flow based motion blur effects that can read the motion data from an .exr file. I normally use this technique for 3D animations but 2D animation programs could benefit from the same tech.
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