Imported Image Sequence of Actor is Transparent

Support Compositing and Post Processing
#1

(Posted earlier in different section but I think I put it in the wrong place)

So I’ve been working on a Star Wars themed project recently and I filmed it against a green screen today. I keyed out everything and exported it as an image sequence.

However, when I bring it into my scene as a plane, light behind it shows through.

1920×1080 216 KB

I assume this has something to do with the alpha channel of the image, but I don’t know enough about this to know how to fix it. I’d like the background to still be transparent while making the actor opaque.

Here is the node set up it came with when I imported it. https://i.imgur.com/qOG72Xu.png

Any help would be appreciated, thank you!

#2

Yes it’s because of the alpha. Why would you need the transparent shader? Can I have a look at the alpha?

#3

Sure! I’ll upload an image of the sequence to a dropbox if that would work? And the transparency shader appears to be there because otherwise the background around the actor is black and not see through.

EDIT: Here is the dropbox link of one of the frames. https://www.dropbox.com/s/raxxuzl17kon8at/KeyedTest10088.tif?dl=0

#4

Using Greater Than to check and you alpha isn’t good.

image
image1600×900 239 KB

I think you should use compositing instead of image as plane with shaders, or better keying to fill the alpha.

#5

How would I go about keying to fill the alpha? Do you mean just rekeying the original video properly so it doesn’t have the damaged looking alpha? Thanks for the response.

#6

Yes, if you want to rekey. Or you can also use texture painting for everyframe in the sequence which I don’t have any experience in that.

#7

It’s all good if you don’t know from the existing information, but do you have any idea what I might have done incorrectly while keying to lead to this? I was following this tutorial. https://youtu.be/RxD6H3ri8RI

Anyways thank you so much, you’ve been really helpful!

#8

My opinion, that guy is a great artist but not a a great tutor. I haven’t used Blender for green screen. I would go with BMD Fusion or Natron for it.

There is a free official tutorial for BMD Fusion keying with project file provided: DaVinci Resolve 17 – Training | Blackmagic Design
I followed the one in the book.

image
image1011×257 102 KB

There are some old Natron keying tutorials on Youtube. Natron is pretty the same as Nuke so you can also use the official Nuke tutorials which are old but still work and have project file. The tutorials can be found on their website and the documentations.
Learn - Nuke Tutorials (foundry.com)

But I would go for Fusion which is easier in most cases. Then you render it out to use in Blender. In Blender, the softwares has to render the composition seperately with the 3D scene, so working and exporting greenscreen footages from other softwares doesn’t make our workflow slower if we calculate.

I can’t really support you in depth because I haven’t do any compoisting for a while.

#9

No worries about supporting me, this is perfect! Thank you for your in depth responses.

#10

Hello, I can’t see your nodes because they have expired, but this is what shows up with the tif that you supplied later in this thread in 2.90.0, in the view port with a emissive plane behind it in rendered view. Looks fine to me, aside from maybe by the feet. Personally don’t have any experience doing this sort of thing.

alpha-shot
alpha-shot1054×844 73.3 KB

and these are the nodes that show up automatically

alpha-nodes
alpha-nodes877×508 52.8 KB

#11

Hmm. The differences in our images might be that I set the image up as an emit object. Thanks for sharing, I’ll investigate a little more!

#12

This is will work.

alpha-shot-II
alpha-shot-II1141×555 52.7 KB

#13

I checked with both setup in Cycles, the one with principled bsdf and the mix shader, both will let light and anything behind it visible.

#14

I’m not sure I understand, but you can’t control the emission strength with the Principled BSDF. I think that’s why I did that.

#15

Thanks for the help, I’ll try that.

#16

Hi, so I rekeyed in premiere, and I’m having the exact same issue again. The alpha channel looks pristine (there’s a little garbage around the feet and the shadow but that’s my poor lighting beforehand).

AlphaChannelPremiere
AlphaChannelPremiere1059×597 27.5 KB
At the very least it doesn’t look as bad as what it was earlier. However, the end result is exactly the same in blender. I know you mentioned compositing in blender, rather than a plane, but does that preclude me from having reflections in my shot? I’d like to keep those if I could.

Thanks a ton

EDIT: Nevermind, I just fixed it with a color ramp node for the alpha, thanks!

#17

You can add an image as a plane to use it as an indirect only to have reflection (or hold out), then add it again in compositing.

#18

That’s smart thanks!