QUOTE(Geeforce @ 03/29/06, 04:17 PM) [snapback]232670[/snapback]
....what am I missing?
Maybe something, maybe nothing at all. Thing is: Z comping doesn't quite work as quick and straight forward as some might want you to believe. Unless you have a lot of action and criss-crossing in your shot, you're better off with a simple alpha in most of the times. If you want/need/have to z comp it, keep the following things in mind:
1.) Z-Channels work black-white as 0-1. 1 being unlimited distance. Many 3D packages render them inverted
2.) Z-Channels can't be anti aliased, since every pixel, even half transparent, needs a definitive depth. If you find your Z channel being not steppy around the edges, you might want to try and divide it by the alpha of the beauty/unpremultiply it. (Which only works if they have been rendered with the same filter kernel)
3.) Z-Channel never works for things like transparency, motionblur etc. since it can't. (Unless you take it really seriously and do what Fusion does and render umpteen passes for it)
4.) Do employ your comp skills. Some blurs here and there, you know... 
Good luck,
FR
