# NAME

GDX_SPHERE - Spherical Surface

# GENERAL DESCRIPTION

A GDX Spherical Surface (GDX Sphere) parametrically defines a sphere using a center point, radius, axis vector, and reference vector.

# DDF SPECIFICATION

    entity 18:0   GDX_SPHERE   "Spherical Surface" {

    double
    CENTER[3];

    double
    AXIS_VEC[3];

    double
    REF_VEC[3];

    double
    RADIUS;

    };

# FIELD DESCRIPTIONS

CENTER

A 3D array containing the X, Y, and Z coordinates of the center of the GDX Sphere.

AXIS_VEC

A 3D array representing the unitized axis direction of the GDX Sphere. Corresponds to the z direction in the parameterization of the GDX Sphere.

REF_VEC

A 3D array representing the unitized reference direction of the GDX Sphere. Corresponds to the x direction in the parameterization of the GDX Sphere. This vector should be perpendicular to the AXIS_VEC.

RADIUS

The radius (R) of the GDX Sphere.

# PARAMETERIZATION

The parameterization is the same as that used for the IGES Spherical Surface Entity (Type 196) and can be found in Appendix G.13 of The Initial Graphics Exchange Specification (IGES) Version 5.2.

# PARAMETRIC RANGE

The GDX Sphere is defined over the following parametric range: 0.0 <= u <= MTH_2_PI -MTH_HALF_PI <= v <= MTH_HALF_PI

# IMPLICIT EQUATION

The GDX Sphere has the following implicit equation: S(x,y,z) = x*x + y*y + z*z - R*R = 0

# RESTRICTIONS

The GDX Sphere is subject to the following restrictions: R > 0.0