When I export an image in Google SketchUp, the radial lines aren't as smooth as in (by example) Vectorworks. How can I make radial lines smoother?
You probably mean the issue, that Sketchup uses straight segments to imitate curved lines. When creating circles and arcs, you can define how many segments you want it to consist, which also defines, how smooth it becomes. For details, see question "How do I change the resolution of circles in Sketchup"