Alpha channel from Gray Scale Possible?

[joysprod]

I have been playing around to try and find a solution where a gray scale image is used as an alpha mask for a video. I just cant find a way of doing it. Played around and tried to understand the Alpha blending mode, but no luck.

I have a live feed producing a gray scale image in silhouette. I want to use this to mask parts of a video that is playing. If this wasnt live I could use Final Cut Pro to turn the black or white to alpha, but it is a live solution I am looking for.

Any solutions?

Peter

[joysprod]

I have managed to get the effect I was after to work using the Texture Mixer Node, but only by copying the one from the Interactive Example!

The one in your example has "Matrix" set as the Transformation setting for both textures. I dont know how you get that as the one from the toolbox only has the options of "identity" or "zero" and no way to set "Matrix". Changing any setting in the Texture Mixer removes the "Matrix" setting and you cannot get it back.

Am I missing something here?

Peter

[lerou]

Getting the color into the alpha channel is not that easy unless you use a shader.

If you load your texture from file: use the image loader and a node called "set alpha mask". Use your image from the image loader as alpha and image source. Convert the resulting image to texture and use it in front of your video texture. Set the texture's shading to custom (Color: Select, Arg1, Current; Alpha: Select, Arg1, TextureColor).

But if you use an external file, you could just change it to contain the information in the alpha channel.

cheers,
rou

[lerou]

For transformations: That is a matrix input. You can connect a matrix from a matrix node (like Scaling) to that input. It will then read "Matrix". If you have no input, you can only select Zero or Identity.

cheers,
rou