4.1 Introduction and table of contentsThis clause describes key concepts in this part of ISO/IEC 14772. This includes how the VRML constructs defined in ISO/IEC 14772-1 are encoded as binary.
See Table 4.1 for the table of contents for this clause.
The following conventions are used throughout this part of ISO/IEC 14772:
Italics are used for event and field names, and are also used when new terms are introduced and equation variables are referenced.
A fixed-space font is used for URL addresses and source
code examples.
The form "0xhh" expresses a byte as a hexadecimal number representing the bit configuration for that byte.
Throughout this part of ISO/IEC 14772, references are denoted using the "x.[ABCD]" notation, where "x" denotes which clause or annex the reference is described in and "[ABCD]" is an abbreviation of the reference title. For example, 2.[ABCD] refers to a reference described in clause 2 and B.[ABCD] refers to a reference described in annex B.
4.2 OverviewA VRML file is structured as defined in ISO/IEC 14772-1 4.2--Introduction.
Every Binary-encoded VRML file shall begin with:
#VRML V3.0 binary <profile> [optional comment] <line terminator>
The header is a single line of UTF-8 text identifying the file as a VRML file and identifying the encoding type and profile of the file. It may also contain additional semantic information. There shall be exactly one space separating "#VRML" from "V3.0" , "V3.0" from "<encoding type>", and <encoding type> from <profile>. Also, the "<profile>" shall be followed by a linefeed (0x0a) or carriage-return (0x0d) character, or by one or more space (0x20) or tab (0x09) characters followed by any other characters, which are treated as a comment, and terminated by a linefeed or carriage-return character.
The identifier "binary" indicates a binary encoding. Wherever character strings are allowed in this encoding, the UTF-8 character encoding defined in ISO/IEC 10646-1 (otherwise known as Unicode) shall be used; see 2.[UTF8]. The usage of UTF-8 is detailed in ISO/IEC 14772-1 6.47, Text, node.
4.3 Binary file syntaxThis clause describes the syntax of binary-encoded, human-readable VRML files. A more formal description of the syntax may be found in Annex A, Grammar definition. The syntax of VRML in terms of the binary encoding are presented in this part of ISO/IEC 14772. The semantics of VRML are as defined in ISO/IEC 14772-1.
Description of binary encoding needed here.
Field, event, PROTO, EXTERNPROTO, and node names shall not contain control characters (0x0-0x1f, 0x7f), space (0x20), double or single quotes (0x22: ", 0x27: '), sharp (0x23: #), comma (0x2c: ,), period (0x2e: .), brackets (0x5b, 0x5d: []), backslash (0x5c: \) or braces (0x7b, 0x7d: {}). Further, their first character shall not be a digit (0x30-0x39), plus (0x2b: +), or minus (0x2d: -) character. Otherwise, names may contain any ISO 10646 character encoded using UTF-8. VRML is case-sensitive; "Sphere" is different from "sphere" and "BEGIN" is different from "begin."
After the required header, a VRML file may contain any combination of the following:
Define binary node syntax here.
Define binary field syntax here.
Define binary PROTO syntax here.
Define binary IS syntax here.
Define binary EXTERNPROTO syntax here.
Define binary USE syntax here.
Define binary ROUTE syntax here.
4.4 Binary VRML files and the World Wide WebThe file extension for binary encoded VRML files is .wrb (for world binary).
The Script node's url field may also support custom protocols for the various scripting languages. For example, a script url prefixed with javascript: shall contain ECMAScript source, with line terminators allowed in the string. The details of each language protocol are defined in the annex for each language. The following example illustrates the use of mixing custom protocols and standard protocols in a single url field (order of precedence determines priority):
Need example of binary encoded Script node here.