NAME

GDX_OFFSET_SURFACE - Offset Surface

GENERAL DESCRIPTION

A GDX Offset Surface represents the offset of a GDX surface entity. This entity is defined in terms of a base surface to be offset and an offset distance. The direction to offset any point on the base surface is determined by crossing the vector obtained by evaluating the partial derivative of the surface with respect to the u direction with the vector obtained by evaluating the partial derivative of the surface with respect to the v direction. the tangent to the base surface at that point.

DDF SPECIFICATION

entity 20:0  GDX_OFFSET_SURFACE   "Offset Surface" {



double
OFF_DISTANCE;



ptr
SURFACE
reftype = (P_SURFS);


};

FIELD DESCRIPTIONS

OFF_DISTANCE

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

SURFACE

The database pointer of the GDX surface to be offset. 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

PARAMETERIZATION

The parameterization is the same as that used for the IGES Offset Surface Entity (Type 140) and can be found in Section 4.28 of The Initial Graphics Exchange Specification (IGES) Version 5.2.

PARAMETRIC RANGE

The GDX Offset Surface is defined over the following parametric range: u0 <= u <= u1 v0 <= v <= v1

   where u0 and u1 are u bounds of the base surface and v0 and v1
   are v bounds of the base surface.

RESTRICTIONS

None.