Menu : SURFACE

Command: Design:Offset

Shortcut : None

This command produces an offset surface of the target surface. The offset surface follows the shape of the target surface, but at a specified distance away on one side of the original surface.

The side on which the offset curve is produced depends on the sign (positive or negative) of the distance. A series of arrows are drawn o the surface (so-called surface normals) indicating the positive side of the surface. A positive distance offsets the surface in the surface normal direction, negative to the other.

The offset surface is always created in Bézier form, even if the original surface is B-spline. The accuracy of the offset surface depends on the number of control points used for the original surface but is also better for the smaller offset distances.

For non-trimmed surfaces, you are given the option to create joining surfaces, which combine the original surface and its offset, forming a closed surface set, like a sheet of material. This is not done with trimmed surfaces, but the trim curves are copied to the offset surface instead.

Offsetting works for a complete element of surfaces, too. You may thus offset a complete model at once. If the surfaces meet each other smoothly, the result will generally be smooth too. Before offsetting several surfaces, you should check all of the surface directions (with command SURFACEÞNormals:Change) so that the offsets will be computed in the same direction for all the surfaces.