IGES - Computer Graphics and Geometric Modeling - page 827

A = 1 , B C D = 0 , = 0 , = 0 , E = 51 .

Because DE is nonzero, we have a closed curve in our plane that happens to be the
copious data entity described above consisting of five points in the plane x = 0.

C.4 The IGES Nongeometric Types

Figure C.10 lists the nongeometric entity types for IGES version 3.0.

Entity Number 406. Property entities can contain numerical or textual data. The
form number specifies the type of property at hand. Low numbers are predefined and
numbers 5001-9999 are left for a user to define. In our case, the form number 5555
is a user-defined property. The first number in the parameter data section after the
entity number is the number of properties. In our case, it is 1 and the property is the
string “01”.

Entity Number 410. A view entity specifies how an object should be viewed. The
projection is assumed to be a parallel orthographic projection. In the view coordinate
system the view plane is assumed to be the plane z = 0 with the origin being the origin
of the view plane. The view direction is along the positive z-direction. The positive y-
axis is the “up” direction. One can also specify a view volume and scale factor. Figure
C.11 shows the layout of the view volume. In the case of our entity, the fact that the
status is physically dependent and the entity use flag is “other” means that a drawing
entity number 404 points to it. See Figure C.12 for a description of the fields in the
parameter data. In our case,

Annotation Entities Structure Entities

Entity type # Entity type Entity type # Entity type

ææææææææææææææææææ ææ æææææææææææææææææ ææ

202 Angular dimension entity 302 Associativity definition entity

106 Centerline entity 402 Associativity instance entity

206 Diameter dimension entity 404 Drawing entity

208 Flag note entity 304 Line font definition entity

210 General label entity 306 MACRO definition entity

212 General note entity 600-699 MACRO instance entity

214 Leader (arrow) entity 406 Property entity

216 Linear dimension entity 308 Subfigure definition entity

218 Ordinate dimension entity 408 Singular subfigure instance entity

220 Point dimension entity 412 Rectangular array subfigure

222 Radius dimension entity instance entity

106 Section entity 414 Circular array subfigure instance

106 Witness line entity entity

310 Text font definition entity

410 View entity

Figure C.10. Some IGES annotation and structure entities.