The key is twinning a texture with its appropriate transparency map. In Bryce, select your model and enter the Materials Editor... Go to the Texture Source Editor and choose a texture you like (2, 3, 4, 7, 8. 9, 13 are appropriate for spacewrecks... Eg, Nurnie-07-col1.jpg ) and its corresponding transparency map (its name will include the letters tr, eg Nurnie-07-tr.jpg)