Chapter 6 -- ENTITIES Section
VERTEX

The following group codes apply to vertex entities. In addition to the group codes described here, see "Common Group Codes for Entities." For information about abbreviations and formatting used in this table, see "Formatting Conventions in This Reference."

Vertex group codes
Group codes Description

100

Subclass marker (AcDbVertex)

100

Subclass marker (AcDb2dVertex or AcDb3dPolylineVertex)

10

Location point (in OCS when 2D, and WCS when 3D)
DXF: X value; APP: 3D point

20, 30

DXF: Y and Z values of location point (in OCS when 2D, and WCS when 3D)

40

Starting width (optional; default is 0)

41

Ending width (optional; default is 0)

42

Bulge (optional; default is 0). The bulge is the tangent of one fourth the included angle for an arc segment, made negative if the arc goes clockwise from the start point to the endpoint. A bulge of 0 indicates a straight segment, and a bulge of 1 is a semicircle.

70

Vertex flags:
1 = Extra vertex created by curve-fitting
2 = Curve-fit tangent defined for this vertex. A curve-fit tangent direction of 0 may be omitted from DXF output but is significant if this bit is set.
4 = Not used
8 = Spline vertex created by spline-fitting
16 = Spline frame control point
32 = 3D polyline vertex
64 = 3D polygon mesh
128 = Polyface mesh vertex

50

Curve fit tangent direction

71

Polyface mesh vertex index. Optional. Present only if nonzero

72

Polyface mesh vertex index. Optional. Present only if nonzero

73

Polyface mesh vertex index. Optional. Present only if nonzero

74

Polyface mesh vertex index. Optional. Present only if nonzero

Every vertex that is part of a polyface mesh has its vertex flag 128 bit set. If the entity supplies the coordinate of a vertex of the mesh, its 64 bit is set as well, and the 10, 20, 30 groups give the vertex coordinate. The vertex index values are determined by the order in which the vertex entities appear within the polyline, with the first being numbered 1.

If the vertex defines a face of the mesh, its vertex flags group has the 128 bit set but not the 64 bit. In this case, the 10, 20, 30 (location) groups of the face entity are irrelevant and are always written as 0 in a DXF file. The vertex indexes that define the mesh are given by 71, 72, 73, and 74 group codes, the values of which specify one of the previously defined vertexes by index. If the index is negative, the edge that begins with that vertex is invisible. The first 0 vertex marks the end of the vertices of the face.