I am having trouble with some Boolean operations. I created an object in ProEngineer and after saving it aa an Lightwave.obj imported it into Bryce. I sized and then positioned it and duplicated and expanded the dup, making the original negative and the larger dup positive. I alligned the pair centered front to rear and left to right and increased the height of the original until it cleared the dup. I then grouped the two. Instead of the "shell" I expected, the negative object disappeared in the render and the positive one remained. Before grouping, both showed as they did after I ungrouped. I created a cube and it worked with both objects as expected when I assigned the cube the appropriate (Positive or Negative) attribute. What is going on? Why will the imported objects work with the cube but not each other? Does it have something to do with them coming from one source ?