This is a common motion graphics effect, but I just can't get it to work!
Ever notice how on any clip with an alpha-ed out background, such as keyed or greenscreened footage, whenever most distort or stylize filters are applied, the effect spills out into the originally transparent (alpha-ed) background? How do I keep the background "clean" (ie: fully transparent) from the effect of the filter which is intended for only the opaque section of the footage?
This happens to me both in FCP and Motion. As a test, I have tried outputting a clip (in animation codec) of a keyed-out greenscreen footage from Motion, opening a new project and re-importing the clip. The result -however- is the same, so the problem isn't from a conflict between the stylize and Keyer filters.
I have also tried another approach: make a duplicate of the keyed-out layer, invert the matte from the keyer (by the way, Primatte RT in Motion does not have an invert matte feature, so I used Blue Green Screen -- any thoughts?), put this layer above the keyed-out greenscreen image, turn it bright white using brightness/luma filters (I am sure there is a better way to do this-- let me know please1), and change its blend mode to "travelling luma" (in FCP) or "stencil luma" or "sillouette luma" (in Motion, the former turns everything black, and the latter reveals only the background I wanted to see through the alpha).
What am I doing wrong here? Share your techniques, pros!
Noah, I outputted the greenscreened clip from Motion using the ProRes422 codec and reimported, but the alpha background was lost! So I did lossless movie + alpha codec output and reimported that. This time, the alpha was perserved, but again the exact same problem occurs when I apply stylize filters!
I have stills of my Motion project settings and examples so you can know what I am talking about exactly. If you feel you need to know better what is happening, I can email you the pics. Just provide your address!
Thank you. By the way, I went to the HD survival Guide website. I assume you are involved with that -- good stuff!