I came from a CAD background myself, and still use CAD to export objects into Bryce. I use a 3d CAD system called SolidWorks that my former company used to use. I got them to buy me a home copy so that I could do my work at home. I left the company several years ago, but I still use the program whenever I want a specific model. I know AutoCAD can export as DXF which several 3D packages can recognize. Bryce is what I use for composing scenes, and I just love it.