Apparantly the 'oldest trick' I learned long ago has been lost from knowledge.
Step 1: export your floor plan to DWG.
Step 2: open that DWG as an object.
Step 3: save the object.
Step 4: place object in floor plan.
Step 5: view object in parallel top down 3d view
Step 6: make sketch render.
Make sure that air perspective is at 0, or you won't see anything.
Pretty sure I found this on the forum 12 years ago.
Erwin Edel, Project Lead, Leloup Architecten
www.leloup.nlArchiCAD 9-26NED FULL
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