# NAME

GDX_EDGE_CURVE - Edge Curve

# GENERAL DESCRIPTION

The GDX Edge Curve entity is used for associating curve geometry to a GDX Edge or GDX Composite Edge Curve.

# DDF SPECIFICATION

     entity 42:0 GDX_EDGE_CURVE "Edge Curve" {

    ptr
    MOD_CURVE
    reftype = (P_CURVES);

    count
    NUM_FACES

    struct
    FACES[NUM_FACES] {

    ptr
    SURF
    reftype = (P_SURFS);

    ptr
    PARM
    reftype = (P_CURVES);

    };

    char
    MOD_PREF_FLAG;

    ptr
    APPROX_CURV
    reftype = (4:0 /* GDX_POLYLINE */);

    };

# FIELD DESCRIPTIONS

MOD_CURVE

The database pointer of the GDX curve corresponding to the model space curve geometry. The allowable GDX entity type/forms consists of the parametercally 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
FACES

Array, dimensioned to [NUM_FACES], containing pairs of GDX surface (SURF) and parameter space curve (PARM) pointers.

SURF

The database pointer of the GDX surface corresponding to the model space curve defined by field MOD_CURVE and the parameter space curve defined by field PARM (if defined). The allowable GDX entity type/forms consists of the parametrically defined GDX surface entities as defined by the P_SURFS ptrlist variable in gdx.ddf. For reference, these entities are:

GDX_NURB_SURF
GDX_SPLINE_SURF
GDX_RULED_SURF
GDX_REV_SURF
GDX_EXT_SURF
GDX_PLANE
GDX_CYLINDER
GDX_CONE
GDX_SPHERE
GDX_TORUS
GDX_OFFSET_SURF
GDX_RECT_TRIM_SURF
PARM

The database pointer of the GDX curve corresponding to the parameter space curve associated with the GDX Edge Curve. 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 (see MOD_CURVE field above). It should be noted, the parm curve explicitly represents the loop. Thus, setting the sense flag in a GDX_COMP_EDGE_CURVE, GDX_LOOP, or GDX_EDGE does not change the interpretted direction of the parm curve.

MOD_PREF_FLAG

Flag indicating whether the model space or parameter space curves are preferred.

PDX_TRUE

The model space curve representation is preferred.

PDX_FALSE

The model space curve representation is not preferred.

APPROX_CURV

This value is for internal use only. This field is used during linear approximation to ensure that the approximation of the edge for all associated surfaces is the same. If a GDX Edge Curve is created without using a corresponding function in the gcr subsystem, this value should be set to MDA_NULL_PTR.

# RESTRICTIONS

None.