NAME

GDX_OFFSET_CURVE - Offset Curve

GENERAL DESCRIPTION

A GDX Offset Curve represents the offset of a GDX curve entity. This entity is defined in terms of a base curve to be offset, an offset distance, and a normal vector. The direction to offset any point on the base curve is determined by crossing the normal vector with the tangent to the base curve at that point.

DDF SPECIFICATION

entity 6:0  GDX_OFFSET_CURVE   "Offset Curve" {



double
PLANE_NORMAL[3];



double
OFF_DISTANCE;



double
T0;



double
T1;



ptr
CURVE
reftype = (P_CURVES);


};

FIELD DESCRIPTIONS

PLANE_NORMAL

The 3D coefficients of the normal vector to the plane from which to offset that base curve. This vector should not be parallel to the tangent of the base curve to be offset at any point along the base curve.

OFF_DISTANCE

The GDX Offset Curve offset distance. This distance may be positive, negative, or 0.0.

The starting parameter of the GDX Offset Curve.

The ending parameter of the GDX Offset Curve.

CURVE

The database pointer of the GDX curve to be offset. The allowable GDX entity type/forms consists of the parametrically defined GDX curve entities as defined by the P_CURVES ptrlist variable in gdx.ddf. For reference, these entities are:

GDX_CONIC

GDX_NURB_CURVE

GDX_ARC

GDX_SPLINE_CURVE

GDX_POLYLINE

GDX_COMP_CURVE

GDX_OFFSET_CURVE

GDX_TRIM_CURVE

PARAMETERIZATION

The parameterization is the same as that used for the IGES Offset Curve Entity (Type 130) and can be found in Section 4.23 of The Initial Graphics Exchange Specification (IGES) Version 5.2.

PARAMETRIC RANGE

The GDX Offset Curve is defined over the following parametric range: T0 <= u <= T1 Note that T0 and T1 must be in the domain of the base curve.

RESTRICTIONS

The curve to be offset must be tangent continuous at all points. For example single point polylines and closed polylines are not valid curves to be offset.

double	PLANE_NORMAL[3];
double	OFF_DISTANCE;
double	T0;
double	T1;
ptr	CURVE	reftype = (P_CURVES);