100

Subclass marker (AcDbSpline)

210

Normal vector (omitted if the spline is nonplanar)
DXF: X value; APP: 3D vector

220, 230

DXF: Y and Z values of normal vector (optional)

70

Spline flag (bit coded):
1 = Closed spline
2 = Periodic spline
4 = Rational spline
8 = Planar
16 = Linear (planar bit is also set)

71

Degree of the spline curve

72

Number of knots

73

Number of control points

74

Number of fit points (if any)

42

Knot tolerance (default = 0.0000001)

43

Control-point tolerance (default = 0.0000001)

44

Fit tolerance (default = 0.0000000001)

12

Start tangent-may be omitted (in WCS)
DXF: X value; APP: 3D point

22, 32

DXF: Y and Z values of start tangent-may be omitted (in WCS)

13

End tangent-may be omitted (in WCS)
DXF: X value; APP: 3D point

23, 33

DXF: Y and Z values of end tangent-may be omitted (in WCS)

40

Knot value (one entry per knot)

41

Weight (if not 1); with multiple group pairs, are present if all are not 1

10

Control points (in WCS), one entry per control point
DXF: X value; APP: 3D point

20, 30

DXF: Y and Z values of control points (in WCS), one entry per control point

11

Fit points (in WCS), one entry per fit point
DXF: X value; APP: 3D point

21, 31

DXF: Y and Z values of fit points (in WCS), one entry per fit point