Problem mixing live video with a movie or picture image the way I want



  • So here is my challenge.  I am designing a theatre production and I want an actor off stage being filmed with a wireless web cam to be projected on screen on stage into an image of a starry night.  It's a comedy, so it doesn't have to be realistic or anything but I definitely need the actor's face to be perfectly clear and not mixed with any part of the starry night.  I made the live video feed a smaller box than the starry night but I can't seem to layer it in front or make it opaque.  I was able to adjust the intensities but there are still parts of the starry night showing on the actor's face.  The layering slider works for the starry night image but doesn't work at all for the video feed.  Any help out there?  I know it's probably a newbie question and hopefully easily answered.  Thanks!



  • The layers work in rather specific way. 0 is the bottom, 1 on the top and so on. You can make the layers opaque or if you use alpha - transparent.  c61a25-layers.izz


  • Tech Staff

    I find that sometimes when changing layers and opacity/blend modes you need to change something, click off the scene and go back on it to see the result. Not sure if this is just me....



  • Dear Damen,

    If the actor is on a black background, I would suggest you use the Luminance Key actor. You can provide the starry night image as the 'background' input, and the web cam video as the 'foreground.' Then adjust the 'key bottom' input until you get a good result. You can also play with the 'softness' input to soften the edge a bit.
    You can also use this actor with layers -- don't provide a background image, and turn the 'alpha' input to 'on'. But when using multiple projectors to layer the images, it is critical when using alpha-encoded images to set the 'blend mode' input of the projector 'transparent.'
    Let us know if you get somewhere based on this advice.
    Best Wishes,
    Mark


  • what background are you using behind your performer's face? a strong, flat colour can be removed using the Chroma Key actor, so you won't need to blend any layers.



  • Excellent.  I'm playing with it at work today without a black background, so I think I can see how it's going to work with one using the Luminance Key and adjusting the bottom variable.  My face looks nice and solid but there is bleed through on my cream colored sweater.  If I can assure that the actor is against a black wall, will it matter what color his shirt will be?  Is this technology similar to what happens with an actor in front of a green screen?  That could also be designed into the set if that would provide the greatest effect but I would like it to be a complete surprise to the audience when it happens.  A green screen would tip them off I'm sure.

    I also have this crazy idea of using a small dot or square, maybe even a picture of a fly, using a mouse watcher to make it fly around the screen and then have the actor squash it against the screen using one of the effects that I stumbled on to that dissolves an image (and of course I can't remember what it was called.)  Think this is even remotely possible?



  • Yes, it's similar to what happens with a green screen. But instead of using color, it's based on the brightness. So, actor on very black background, and no black clothing, and a decent bit of lighting should get you what you want.

    Best Wishes,
    Mark
    P.S. If they have black hair, tell them they have to dye it. ;-)


  • So if I make the actors dye their hair bleach blonde, that should work great, right?  ;-)

    Here's the update:  It is almost working using the Video In Player, a Movie Player, the Luminance Key and a Projector.  However, you guessed it, my dark brown hair is replaced by the background image as well as bleed through in other spots occasionally.  I'm so close but it's not quite performance-quality yet.  I definitely need a solid image of the actor in the foreground no matter what happens in the background.

    Any ideas on how to fine-tune it?  I have played with the bottom variable as much as I can.  I've also played around with the Video In and Movie Player connected to their own Projectors and modified the intensity, but that's worse than the Luminance thus far.  I have not tried the layering option yet the way that Mark suggested:

    "You can also use this actor with layers -- don't provide a background image, and turn the 'alpha' input to 'on'. But when using multiple projectors to layer the images, it is critical when using alpha-encoded images to set the 'blend mode' input of the projector 'transparent.'"

    I'm not quite clear on all the steps there.  Is that using Video In, Movie Player connected to their own Projectors without the Luminance?  Or a Luminance Key for both Video In and Movie Player to their own Projectors?  Need more specific instruction on that.

    The director and cast are thrilled about the idea, so I'm determined to make it work somehow.  We're going to try this weekend using an IPhone App to broadcast to my computer through Isadora to the projector and screen.  If that works, we ultimately don't even need a background image to make it work but it would be better with one.

    Thanks for the help!

    Pat



  • Actually, just as I posted the previous update, I wondered if my method of adjusting the key bottom variable matters.  I mostly used the slider option to adjust it but now I remember there is another way to adjust by smaller increments right?  How do you adjust in tenths of a percent?



  • And to answer dbini's question.  The actor will be sitting in front of a black wall most likely.  The projection will be darkish too most likely but I haven't chosen it yet.  I've been using a projection of Central Park which we are using for the current production just to try it out.  Maybe that's too sunny and bright to work with the Luminance Key?


  • Tech Staff

    @damendeman

    For smaller increments click into the actor field while pressing the shift button, now moving the mouse enables "fine tuning".

    Best
    Michel


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