CompuServe Messages

The POLYLINE entity has several variations. At the beginning of the POLYLINE definition before the vertex data, there will be a group code 70 followed by an integer number. That number is a flag to describe the type of polyline. Values from 0-7 mean its a 2D POLY. Values from 8-15 mean its a 3D polyline. Values between 16 and 63 mean that its a rectangular face mesh. Values 64 and greater mean that its a arbitrary polygonal face mesh like 3DS uses. DXF3DS will convert 2D Polylines into faces objects, and convert the other meshes into faces, but not convert 3D polylines. One other thing about 2D objects in AutoCAD DXF, even though they contain no Z information, they can be located at any point in 3D space and in any orientation based on a cross product of the 3D point and the group 210 codes, simplified in an arbitrary but reproducible way. In fact, you will see that the POLYLINE header always has a group 30 code for the Z axis, even for a 2D poly, and always has 210 codes. -GB-