# NAME

GDX_CURVE_BOUNDED_SURF - Curve Bounded Surface

# GENERAL DESCRIPTION

The GDX Curve Bounded Surface is comprised of a parametric GDX surface and one or more GDX Composite Edge Curve (boundary) entities that define the active region of the surface.

A GDX Composite Edge Curve corresponding to the outer boundary may or may not be explicitly specified. Any number of GDX Composite Edge Curve entities corresponding to inner boundaries may be specified. If desired, the outer boundary may be implicitly defined to be the natural boundary of the corresponding base surface via the IMPLICIT_OUTER flag. For certain types of closed surfaces it may not be possible to identify any given boundary as outer.

The active region of the GDX Curve Bounded Surface is defined to be the portion of the base surface in the direction of N x T from any point on the boundary, where N is the surface normal and T the boundary curve tangent vector at the point.

For a closed surface, the sequence of parameter space curves corresponding to a single GDX Composite Edge Curve do not have to be continuous and closed in parameter space. If this is the case, however, the parameter space curves must be able to form a continuous and closed boundary in parameter space by adding the appropriate sections of the seam curves.

# DDF SPECIFICATION

    entity 45:0 GDX_CURVE_BOUNDED_SURF "Curve Bounded Surface" {

    ptr
    SURF
    reftype = (P_SURFS);

    char
    OPEN_SURF;

    char
    IMPLICIT_OUTER;

    char
    FIRST_IS_OUTER;

    count
    NUM_OF_BOUNDS;

    ptr
    COMP_EDGE_CURVE[NUM_OF_BOUNDS]
    reftype = (43:0 /* GDX_COMP_EDGE_CURVE */);

    };

# FIELD DESCRIPTIONS

SURF

The database pointer of the GDX surface to be bounded. 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
OPEN_SURF

Flag indicating whether or not the base surface is open (in both u and v directions).

PDX_TRUE

The base surface is open (in both u and v directions).

PDX_FALSE

The base surface is not open (in either u or v directions).

IMPLICIT_OUTER

Flag indicating whether or not the outer boundary corresponds to the natural boundary of the base surface.

PDX_TRUE

The outer boundary corresponds to the natural boundary of the base surface (and a corresponding GDX Composite Edge Curve is NOT contained in the list of GDX Composite Edge Curve entities referenced by the COMP_EDGE_CURVE field.

PDX_FALSE

The outer boundary does not correspond to the natural boundary of the base surface.

FIRST_IS_OUTER

Flag indicating whether or not the GDX Composite Edge Curve database pointer stored in COMP_EDGE_CURVE[0] corresponds to the outer boundary.

PDX_TRUE

The GDX Composite Edge Curve database pointer stored in COMP_EDGE_CURVE[0] corresponds to the outer boundary.

PDX_FALSE

The GDX Composite Edge Curve database pointer stored in COMP_EDGE_CURVE[0] may not correspond to the outer boundary. In fact, there may not be a single outer boundary.

NUM_OF_BOUNDS

The number of boundaries in the GDX Curve Bounded Surface.

COMP_EDGE_CURVE

Array, dimensioned to [NUM_OF_BOUNDS], containing GDX Composite Edge Curve database pointers corresponding to the boundaries of the GDX Curve Bounded Surface.

# RESTRICTIONS

The GDX Curve Bounded Surface is subject to the following restrictions: if IMPLICIT_OUTER = PDX_TRUE NUM_OF_BOUNDS => 0 OPEN_SURF = PDX_TRUE FIRST_IS_OUTER = PDX_FALSE else NUM_OF_BOUNDS > 0