Transparent background animations

Transparent background animations

Hi,

I really just started today with Cheetah3D, and since I am the impatient guy :wink:, I already have a question:

How can I make a movie with transparent background?

The reason is, I will often include my images into Keynote presentations, which makes very nice to have a transparent background, so that the slide's background shows through the image.

This works fine with still images: in the camera render setting, I select the background color, and in the color picker, I drag the transparency slider all the way to the left (to zero). A simple copy and paste later, boum, I have a transparent-background image in my Keynote slide. Great.

Now, I couldn't make it work with movies. It seems I can set a transparent background color in the camera render settings. This gives the animation a "black" background from the render window. But then, I'm stuck:

- copy and paste only pastes a still image, not a movie.
- saving the movie (converting to quicktime movie, default parameters) yields a movie, but its background is not transparent.

Any idea? A quick search through the help and this forum didn't show up anything, but I would be glad to RTFM if I could be given a pointer.

A zillion thanks,

Jean-Denis
 
Select the camera you'll be using to render the movie, select its background color, and make its opacity 0%. (You figured that bit out, I see.)

You'll need to pick a video codec that supports alpha channels, such as PNG, Animation, TIFF, or JPEG 2000 (you need "Millions of Colors+" -- "+" meaning "alpha channel"). I think you can only "get to" PNG or JPEG 2000 from inside Cheetah 3D; PNG is lossless, so you can recompress PNG to a better format from QuickTime Pro or whatever.

Note

In general, codecs that support alpha channels aren't designed for "final delivery" which means that playback speed and small size aren't major considerations. The Animation codec is an exception, but it's one of the original codecs (i.e. QuickTime 1.0) and is pretty terrible (it creates huge movies in lossless mode -- bigger than PNG!, and loses quality quickly without saving much space as you lower the quality). I just tried JPEG 2000 for the first time while checking my response to your question -- a 4s animation 640x480 at high quality weighed in at 3MB.
 
Last edited:
Cool

Oh my, this is so cool!

It works.

Of course, I hadn't paid attention to the Codec. The default one was H264, which doesn't support an alpha channel.

This might make a small footnote in the online help :)

In any case, many, many thanks.

JD
 
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