Changing the background for Alice movies

You can create an Alice movie that has a green or blue screen as the background (delete the ground and maybe change the atmosphere color). Then use
chromakey to replace the background of the movie with photos of real places.

Step 1: Create your Alice movie in Alice 2.2

Step 2: Edit the preferences in Alice to set the size of the display window to 640 by 480 or to the size of your background picture.
Click on Edit and then preferences.

You will see the preferences window.

Make sure that the "Delete frames folder after exporting video" checkbox is not checked. Alice will by default delete your video frames after you close
the video capture window unless you uncheck this.
Also set the width and height of the render window to 640 by 480 or the size of the background image
Close the preferences window.

Step 3: Delete the ground and change the atmosphere if necessary.
Right click on the ground in the object tree and select "Delete"



The ground will be deleted.


The rockettes don't have any blue on them so we can use the blue background in this case. But, sometimes you will want to change the atmosphere color to green (if your Alice objects have blue in them). To do this select the world in the object tree and then click on properties in the worlds details area. You can select green for the atmosphere color.


Step 4: Export the video frames to a directory
Click on File and then on "Export Video"

Alice will ask where you want to save the current world and then save the current world in that directory.

It will display the export video window. Click "Record" to start recording the frames and "Stop Recording" when you want to stop.
The video frames will be saved in a directory called "frames" in the same location that you saved the world.


Step 5: Create a new movie by doing chromakey on each frame of the Alice movie. Here is an example program that loops through all frames in a directory and does chromakey on each frame.

Step 6: Write out the final movie

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Last modified 7 March 2009 at 10:14 am by ericson