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Can 4.5 Video Textures support alpha channels?

Is it possible to use alpha channels in 4.5 video textures to have part of the video be transparent?

Somebody in the forums mentioned you could run an alpha video in the opacity node in UE3--would the same type of solution work here?

Thank you!

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asked Oct 14 '14 at 10:20 PM in Using UE4

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avatar image elysebk Dec 17 '14 at 06:05 PM

As of 4.6 it seems like you still can't use any video with an alpha channel. I am currently using a second b&w "alpha" video file and plugging that into the opacity. This works ok, but there seems to be a slight delay between the video files in the material, causing them to not sync 100%.

Can anyone give us more info on if there are plans to add support for videos with alpha?

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6 answers: sort voted first

Hello kinjutsu,

The Media Textures are implemented as regular UTextures so so you can use all the features of the Material Editor to fake something, much like you mentioned you already have done.

Alpha channels for the textures is currently not on the road map for future implementation since there are other ways to 'fake' this effect.

Here is some extra documentation and insight on ways to go about creating this effect.

Forum Post


External Posts





Andrew Hurley

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answered Jan 19 '15 at 08:47 PM

avatar image Etienne Andlau Jul 31 '15 at 08:14 AM


My solution was to import a .avi file with embedded alpha channel. Then right click on the icon in tray and select "create media texture" Create BSP brush, a box in your map. Just click to select texture and drag it onto the surface. Material is created. Double click on material icon in tray and blueprint of material comes up. Click to select material. Left side, select "masked" The alpha from the .avi can now be connected. Works fine.

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avatar image CodeSpartan Sep 29 '15 at 01:15 AM

Can you please tell which settings did you use for .avi encoding? I've tried different presets, and it either doesn't open at all in UE4 or is without alpha...

avatar image Etienne Andlau Sep 29 '15 at 01:22 AM


I pulled a key on a green screen in After Effects CS3 using the Keylight plugin from the Foundry. Then I rendered the clip out of After Effects as an .avi with RGB + Alpha selected. So the alpha channel was embedded into the .avi file. That worked fine inside U4. I have the project files somewhere I have to go dig them out. If you have any more problems let me know and I can send you the actual script files.

avatar image Etienne Andlau Sep 29 '15 at 01:23 AM

What program are you using to encode / embed the alpha channel into the .avi with?

avatar image Etienne Andlau Sep 29 '15 at 01:30 AM

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settings.jpg (156.6 kB)
avatar image Etienne Andlau Sep 29 '15 at 01:31 AM

I am not sure if I premultiplied the alpha or not. Cant remember but you could try both and see which works.

avatar image Etienne Andlau Sep 29 '15 at 01:33 AM
  1. Clip with girl against green screen.

  2. Bring into After Effects.

  3. Used Keylight to pull green screen (just one click. I wasn't trying to pull a really good key.)

  4. Rendered out as .avi with RGB+Alpha selected.

  5. Drag .avi into content browser of U4. (Wait a second for cursor to change from error to o.k.)

  6. It shows up as Media file.

  7. Right click on the icon in content browser and select "create media texture".

  8. Another icon appears next to it. Its a media texture now.

  9. Double click on the media file icon and a player opens up.

  10. Play file in the viewer popup and set to loop.

  11. Then close the popup viewer. (its still playing after you close the player)

  12. Create BSP box on your map.

  13. Drag media texture icon over and onto the surface of the box.

  14. Another icon appears in the content browser now.

  15. Its a material now.

  16. Double click on the material icon in content browser.

  17. Blueprint opens up.

  18. Set the material in the properties bin on the left as "masked".

  19. The mask input on the material node will now be accessible.

  20. Connect the alpha output to the mask input in the material node.

  21. Click on "apply".

  22. After a few seconds you will see the projection with transparency playing on your box actor in the main viewer.

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Rendered out as .avi with RGB+Alpha selected takes a lot of space, any format with compression and alpha is supported?

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answered Dec 07 '17 at 12:30 PM

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I haven't tried any other format besides .avi but 4.18 have a major rework of the media framework so a format like .mp4 might work. If it doesn't I would just render out a black and white matte layer and bring that into U4 as another movie file. Then in the material editor I would plug the black and white into the opacity input of the material and see if that will create an alpha for you. You can "math around" with the nodes in the material editor and see if you can create an alpha sure its possible.

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answered Dec 07 '17 at 12:39 PM

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Etienne Andlau
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thanks Etienne Andlau my use of this is to get a chroma key in AE using keylight, in case I would use 4.18 is there any plugin to do this chroma key inside UE4? what would be the most effective way to do it? node bluescript or a tool/setting inside ue4 4.18?? what is your exp?

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answered Dec 07 '17 at 12:44 PM

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Keylight is great I use that in AE in visual effects a lot. Its in Nuke too. I would pull the key outside U4 and bring it in but if those two videos work out for U that might work too. I suspect if you do it inside U4 you will need a perfectly lit green screen. Don't think U4 is meant to work as well as Keylight but you can try :-)

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answered Dec 07 '17 at 12:59 PM

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Etienne Andlau
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avatar image marcoszn Dec 07 '17 at 01:08 PM

I would like to achieve something close (far close) to this https://www.youtube.com/watch?v=SC6T-D2pnIw , they uses a clean frame of your footage and creates a matte, according to that frame, instead of picking only one keying color, and adjusting tolerance and softness values.

avatar image Etienne Andlau Dec 07 '17 at 01:14 PM

Yeah pulling good green screen keys is a whole art in itself. I have spent tons of time cleaning up poorly shot green screens and rotoscoping is almost always needed. If your green screen "needs a lot of work" I would just do get a nice clean matte in AE then use it to fill the background in with a flat and solid degrained green and render that movie out for import into Unreal 4.

avatar image Etienne Andlau Dec 07 '17 at 01:16 PM

... then once in U4 just pull the green with nodes as shown in those videos. There are no silver bullets for green screens just bul s hit marketing out there :-)

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If you do want to do the chroma key pull inside Unreal I would use Keylight in AE to pull a really good matte and then inside AE fill the background using matte with a nice solid green with no grain on it. I would also degrain the footage in the foreground. Then bring the footage into U4 with the solid clean green background. You also bring 3 movies in one for each color channel ad play around in the material editor and see what happens if you combine them. :-)

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answered Dec 07 '17 at 01:08 PM

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Etienne Andlau
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