Topic: Extrusion Direction in Polyline

[mailmaverick]

I was working on a drawing containing some polylines (all with elevation Zero). But when I tried to do FILLET on them, it gave me error : "Two entities are non coplanar." When both elevations are ZERO, how can the entities be non coplanar ? After lot of researching and mind boggling, I came to know about DXF Code 210 i.e. Extrusion Direction, which was different for both polylines. The Extrusion Direction was : (210 -0.000612033 -0.0323764 0.999476). I also saw that even if elevation of Polyline was Zero, when i click on any of its vertices, the Bottom Left Portion of Screen showed Coordinates having non-zero Z value. Please note that I am entirely working in 2D.

The moment I modified the Extrusion Direction to (210 0 0 1), it was OK and Z cordinate of all vertices changed to Zero.

Now I have two questions :-
1.) What is the meaning of Extrusion Direction ?
2.) If Elevation of Polyline is Zero, why the coordinates of vertices show non-zero Z values ?

[gile]

Hi,

The extrusion direction is the normal vector of the polyline plane (the vector perpendicular to this plane).
The polyline elevation is the signed distance from WCS origin to the polyline plane.

If you draw a polyline on the YZ plane containg the WCS origin (command: UCS > Y > 90 > PLINE), this polyline will have a normal (extrusion direction) equal to the X axis (210 1.0 0.0 0.0) and an elevation equal to 0.0 (38 . 0.0).

You can also see this thread.