OFF File Format Summary

Also Known As: Object File Format


Type Scene description
Colors NA
Compression Uncompressed
Maximum Image Size NA
Multiple Images Per File NA
Numerical Format NA
Originator Randi Rost
Platform UNIX
Supporting Applications dxmodel, others
See Also MTV, Pixar RIB, POV, PRT, QRT, Radiance, RTrace

Usage
Description of 3D scenes for later rendering.

Comments
The OFF format is designed to support easy and flexible description of 3D objects for later manipulation and rendering.

Vendor specifications are available for this format.

Code fragments are available for this format.


OFF (Object File Format) was developed in 1986 at Digital Equipment Corporation's Workstations Systems Engineering by Randi Rost and was subsequently made available for public distribution. OFF is partly derived from an object file format used at Ohio State University. OFF was designed from the start to support data interchange and archiving; in this case, the interchange and archiving of 3D objects. Although this plan originally bore fruit inside Digital, OFF has seen use in the 3D modeling community, partly because of its wide availability on the Internet.

Contents:
File Organization and Details
For Further Information

The OFF author thought carefully about how to establish libraries of laboriously-produced 3D objects so that the labor that went into construction of the objects could be amortized through reuse. OFF files consist of lines of ASCII text describing objects, implementing part of the author's goal of making OFF independent of language, device, and operating system.

The format is well described in the original specification documents included on the CD-ROM, and only a summary of that format is included here.

File Organization and Details

An OFF file consists of a number of ASCII lines. The following are usually found at the beginning of these lines:

Name

Short descriptive name of object defined in the file

Description

Fuller description of the object defined in the file

Author

Actual author or company owner

Copyright

Distribution information

Type

Object type; currently, only polygons are supported

Following this information is a series of lines, each defining an object attribute. Each attribute consists of:

Property name

Uniquely describes the property; currently, conventions exist for geometry, polygon colors, vertex colors, back faces, vertex order, diffusion coefficients, specular coefficients, and specular power

Property types

One of the following: default, generic, indexed, or indexed_poly

Data format

String of characters indicating the order and type of the data to follow

Filename or data

The file indicated here may contain more elaborate data than might be appropriate in this file.

Associated with the original OFF system are an include file, objects.h, and a library file, off.a (on UNIX systems). Together, these implement a subroutine library for reading and writing OFF files. You can adapt these for operating systems other than UNIX.

For Further Information

For further information about the OFF format, see the specification included on the CD-ROM.

Rost, Randi, OFF--A 3D Object File Format, 6 November 1986, updated 12 October 1989.

You can also obtain the OFF archive (containing the distribution format, tools, and objects) via FTP from:

ftp://gatekeeper.dec.com/pub/DEC/

The OFF author, Randi Rost, is not currently supporting OFF or enhancing its tools (nor is Digital Equipment, where Mr. Rost developed OFF). The archive can be used freely, but comes with no express or implied warranties. You must adhere to the usage guidelines outlined in the copyright sections of the individual files.

For further information, contact:

Randi Rost
Kubota Pacific Computer, Inc.
2630 Walsh Avenue
Santa Clara, CA 95051
Email: rost@kpc.com


This page is taken from the Encyclopedia of Graphics File Formats and is licensed by O'Reilly under the Creative Common/Attribution license.

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