# NAME

GDX Entity Overview

# OVERVIEW OF GDX ENTITY DEFINITIONS

The GDX geometry and topology entities have been designed to facilitate neutral representation of the various geometric and topological entities used in CAD/CAM systems and data exchange standards. Further, the GDX entities and corresponding functions have been designed with considerations of efficiency and numeric stability.

# GDX ENTITY CLASSIFICATIONS

Parametric Curve Entities

| GDX_CONIC | Parametric Conic Arc
| GDX_NURB_CURVE | General Rational B-Spline Curve
| GDX_ARC | Parametric Circular Arc
| GDX_SPLINE_CURVE | Parametric Spline Curve
| GDX_POLYLINE | Polyline Curve
| GDX_COMP_CURVE | Composite Curve
| GDX_OFFSET_CURVE | Offset Curve
| GDX_TRIM_CURVE | Trim Curve

Parametric Surface Entities

| GDX_NURB_SURF | General Rational B-Spline Surface
| GDX_SPLINE_SURF | Parametric Spline Surface
| GDX_RULED_SURF | Ruled Surface
| GDX_REV_SURF | Revolved Surface
| GDX_EXT_SURF | Extruded Surface
| GDX_PLANE | Plane Surface
| GDX_CYLINDER | Cylindrical Surface
| GDX_CONE | Conical Surface
| GDX_SPHERE | Spherical Surface
| GDX_TORUS | Toroidal Surface
| GDX_OFFSET_SURF | Offset Surface
| GDX_RECT_TRIM_SURF | Rectangular Trimmed Surface

Curve Bounded Surface Entities

| GDX_CURVE_BOUNDED_SURF | Curve Bounded Surface
| GDX_COMP_EDGE_CURVE | Composite Edge Curve
| GDX_EDGE_CURVE | Edge Curve

Topology Entities

| GDX_SOLID | Solid
| GDX_SHELL | Shell
| GDX_FACE | Face
| GDX_LOOP | Loop
| GDX_EDGE | Edge
| GDX_EDGE_CURVE | Edge Curve
| GDX_VERTEX | Vertex

Surface Approximation Entities

| GDX_CURVE_MESH | Curve Mesh Surface
| GDX_RECT_MESH | Rectangular Surface Point Mesh
| GDX_FACET_SHELL | Facet Shell Surface
| GDX_POLY_SHELL | Polygon Shell Surface

# GDX_MATRIX

The GDX GDX_ARC and GDX_CONIC entities contain a matrix field that corresponds to a GDX_MATRIX. GDX_MATRIX is a typedef provided by the gdx_Interface.h include file and is defined as follows: typedef double GDX_MATRIX[12];

The fields of the GDX_MATRIX are stored in the order as illustrated below:

    | R00 R01 R02 | | Xinput |   | Tx |   | Xoutput |
    | R10 R11 R12 | | Yinput | + | Ty | = | Youtput |
    | R20 R21 R22 | | Zinput |   | Tz |   | Zoutput |
    GDX_MATRIX[0] = R00
    GDX_MATRIX[1] = R01
    GDX_MATRIX[2] = R02
    GDX_MATRIX[3] = Tx
    GDX_MATRIX[4] = R00
    GDX_MATRIX[5] = R11
    GDX_MATRIX[6] = R12
    GDX_MATRIX[7] = Ty
    GDX_MATRIX[8] = R20
    GDX_MATRIX[9] = R21
    GDX_MATRIX[10] = R22
    GDX_MATRIX[11] = Tz