Hi David,
In RED, all tracks feature both upstream and downstream masking, so you can place the mask in either pre or post transform slots, with the order of render being: media, upstream mask, transform, downstream mask.
If you create a 3D plane shape and twirl down the top track level, you will notice that there is a mask sub-track and then the transform controls track and then the face sub-track and if you twirl down the face sub-track you will notice that there is another mask sub-track and then the media sub-track.
Spline shapes placed on the face (upstream) mask are subject to transforms made to the track, while spline masks that are placed in the top (downstream) mask are not transformed with the shape. If you want the spline shape to lock on to the media then you place it in the face mask (upstream), if you want the mask to remain static (like a letter box for instance) then you place it on the top mask (downstream.)
And here’s another tip – there are tracks and containers in RED. Tracks have a media element, such as image clips, static images, EPS files, text etc, while containers are group controllers (similar to a null object) for 1 or more tracks. There are three types of containers – “Standard 2D” container for grouping flat 2D tracks, “3D” container for extruded elements and also for 2D/3D layer interaction in 3D space, and “Title” containers for automating rolls/crawls etc. In a 3D container, you can have extruded text or extruded vector art along with 2D objects all of which can be animated in 3D space along with the lights, camera and shadows.
I believe you’ll find that RED is quite a robust compositing solution and with a little practice you should be able to use this software to complete highly sophisticated composites.
Cheers,
Peter.