Sadicus, Bryce won't do a true Z-depth. You can get close with "Distance Mask". Are you using Photoshop? You cannot do a shadow pass, or a color pass. You can isolate objects for masking using "Object Mask". You can isolate the sky, or run Depth-of-Field filtering, using Distance Mask and in PS, the "Select by Color Range" option. Show us a screenshot of your project and it will help us help you!