There is a fairly easy approach to simplifying models from other 3D modeling software and getting them into Sketchup. Here is a step by step process for exporting an AutoCAD model and simplifying it in Sketchup in order to upload it to Concept.
- Export the AutoCAD model as a .DWG file
- Import the .DWG in Sketchup (a function available for free on Sketchup 7, but only in the Pro version of Sketchup 8)
- Create a cross-sectional plane parallel to the ground in Sketchup
- Lower the cross-section down to an elevation that isolates the building footprint while eliminating extraneous objects (structure, mullions, etc.)
- Right click on the cross-section and 'Create Group from Slice'
- Move the slice away from the original model and copy it
- Create a new Sketchup model and paste the copied slice into it
- Delete any extraneous lines from the building footprint and complete the polygon surface
- Extrude the footprint up to the building height, and then modify the roof and windows as needed