This section refers to settings that are specific to AutoCad drawing (DWG) and AutoCad exchange (DXF).
Autocad Exchange Import
Convert LWPolylines to blocks
An AutoCad Polyline entity is made up of a series of connected lines and arcs. Normally when these are imported into Impact these lines and arcs will lose their association and simply become individual entities. This option causes a new sub-block to be created for each Polyline entity into which the lines and arcs will be added. This means that you can still treat them as a single entity if necessary.
Use more accuracy for B-Splines (recommended)
AutoCad files can contain B-Spline entities. However, Impact has to convert these to entities (arcs and/or lines) that give an approximation of the original shape.
This option is on by default, but if you switch it off this will reduce the number of entities used in the approximation. The downside of this is that the approximation will be less accurate.