Topic: Normals calculated within Lisp

[S.Langhammer]

Hello again!
With a lot of help I finally managed to fetch all entities and sub-entities from a drawing I Need. HURRAY!
Well now comes the next tricky part:
I need to find the normal vectors from arcs circles and ellipses, to determine how they are positioned in a 3D space.
I know AutoCAD has a commans named "nor" to get this information, but I'm bound to BricsCAD so this is not an Option.

Might anyone know a way to get the normals from ellipses, circles and arcs? Or maybe just a more or less intelligent way to eget 2 points on the lines of arcs, circles and ellipses? I mean I do get a center point from each of those, if i had 2 more points on the line of the arc/ellips/circle i could just pass all 3 to a file and calculate the normal vector within the Delphi program, thats reads the exported information at the end.

[Lee Mac]

DXF Group 210 stores the WCS unit normal vector for planar objects and is used to calculate the OCS for the entity (via the Arbitrary Axis Algorithm); alternatively, you can calculate the normal vector by calculating the vector cross-product of two vectors spanned by three points defining the entity.

[S.Langhammer]

Thanks,
I red on autodesk.com that the dxf group code 210 is the extrusion direction, but the translation my dictionary gave me didn't actually fit the topic.