Geom::Transformation.new( origin, zaxis ) <- that isn't a rotation transformation. To rotate you must use one of these formats. Geom::Transformation.new( pt, axis, angle ) Geom::Transformation.rotation( point, vector, angle ) https://developers.google.com/sketchup/docs/ourdoc/transformation#rotation But what is not clear is this: "how to rotate an object in the direction of the cursor" What do you mean by this?