3D Graphics Programming with QuickDraw 3D 1.5.4

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Labels

ASCII

Type

Binary

type ( = 0x74797065 )

Data Format

typeID

A negative integer. No two type objects in the same file may have the same value in this field.

owner

An ISO 9070 owner string. The value of this field may not occur in any other type object. The string must not contain a # character, which is used to demarcate comments in 3DMF.

Data Size

4 + sizeof(String)

Description

Type objects are used only in conjunction with custom objects, and have a role only in binary metafiles. The purpose of the type object is to establish a correlation between the dynamically-allocated 4-byte type identifiers used to identify types in binary metafiles, and the text string type identifiers that are the fundamental type identifiers in 3DMF and QD3D. That the text string is the sole identifier of a custom type, and the 4-byte quantity is only dynamic, is a feature that is new in Version 1.5. By dynamic we mean that the 4-byte identifier is created anew each time the custom object is registered by an application. A key point is that the 4-byte type identifier need not be constant from metafile to metafile, or from session to session. The 4-byte type identifiers are negative numbers, starting with -1 and decreasing by 1.

The reason there is no need for type objects in text metafiles is that the 4-byte identifiers do not appear at all in text metafiles. So there is no need for a type object that establishes a correlation between a 4-byte identifier and a text string identifier.

This functionality, which is new in Version 1.5, is reflected in the new ways of registering custom objects in QD3D 1.5. Otherwise, it is transparent to the user of the QD3D API.

Parent Hierarchy

3DMF.

Parent Objects

None.

Child Objects

None.

Example