Cineversity

I have a live action video texture of a figure (on green-screen) that I am projecting onto a panel and using the alpha channel created in Premiere to mask out the panel so that the figure now appears to be on a virtual set. The problem is that the edge of the alpha mask has a dark outline that does not appear in the video file (see attached). It’s more noticeable when the figure moves, as the outline undulates around it - particularly in the hair.

I thought this might be an artifact from Premiere so I re-exported the color channel with a matching color background behind the figure (i.e. matching the virtual set), but now it’s a glowing highlight instead of a black outline (see attached).

I’m sure it must be a simple settings issue in the materials editor since I always get flawless alpha channels out of Cinema.

Thanks.

Hi mford610,

Often it is just a handling of the material, e.g., a gamma was applied to a the alpha channel, or even a complete wrong color profile. Note that C4D assumes, as long as not color profile is included that it is sRGB or Linear. sRGB is not a video profile, and no, it is not so close as some people might wish for to REC709. Have you specified all the material? How is it if you compose it in Ae, with the correct setting and a medium dark red background?

Without a short clip (a second) I rally can’t tell. But my gut feeling is, that it is a problem outside of C4D.
Do you need an upload link? Please note that I do not use anything else than Amazon’s cloud or Dropbox.

All the best

I sent you a reference project stripped of everything extraneous via your Dropbox link. Still 19MB due to the video sample. Sorry about that.

I agree that the problem may be outside of Cinema. The sample file I attached is cleaner than the original source I was using in the full model. I have attached a JPG frame from the video as it appears in Premiere (composited with a background). And it doesn’t look much different than what I’m seeing in Cinema with this sample project. So it may just be a ratty greenscreen mask.

NOTE: When I render with shadows turned on, the masked-out part of the polygon still casts a shadow. So instead of a shadow of the projected figure, I get a shadow of the square polygon. Is that to be expected? After all, the alpha is not the same as a boole.

Thanks!

Hi mford610,

This is an keying problem. I would suggest to start over. Some people suggest to “Choke” the the matte, but that is of course just low quality.
If you open you footage in After Effects and place a black background behind it, you will see the fringy edge. Switch the black layer on and off to see the effect, right shoulder is the a good place to see it. It is four pixels off.
This edge is the main area of a key, pretty much anything around it (the green screen) can normally taken out with a garbage matte. To get this right, often the hair, transparent cloth parts and the body itself are split into separate keys. It looks like it was taken from a HD, if you have the 4K, key this one, if you have 6K or 8K use this, always from the most raw/source file. Never from a graded footage.
Something that I don’t get, why to use a nearly white noisy background into the footage, when everything else in the image is dark or mid-tone?

The Light setting has a soft shadow in it. The soft shadow is the least quality you can get. It is based on a evaluation of the samples it takes. Object or not is the first evaluation, with distances between. These sample points, if the was no object, but then there is a shadow casting object, are the precision you get, as the shadow is calculated between these to samples. Always smooth among all points. It is kind of a fake, and back in the early nineties a needed option to deal with 80mhz CPUs. Today, I found this light source to be not something I would suggest for too many reason; But yes it is fast. Your settings of the Map (the raster) is 250x250, the lowest as well.
The last time we discussed this here was in this thread:
https://www.cineversity.com/forums/viewthread/2909/

As a side note, the project I have received uses sRGB, which is not an HD standard. It is not REC709. The curve in both is especially different in the darks. Not that I see any solution here for the problems mentioned above, but it is part of the mix.

Having said all of that, here is a little dirty trick to make it work, add a filter to the Alpha channel, and set it up as shown in the image. It is a trick, not the way I would suggest to work, but if a deadline or such is close, that is one way.
https://www.amazon.com/clouddrive/share/ezCRm9vcwUfoeb4DMAopr58SL0Z1cK3RGUwABcTjLkh
(I pixelated the footage content, not suggested as procedure)

All the best