Project Freewheel: How does it work?

When Project Freewheel was first unveiled, many readers first asked: How does it work? The question still comes up today. Back in my days when authoring Beyond the Paper, Software Architect, Ben Cochran, and I provided a high level overview:

1. Using just his browser, a user sends an URL (Uniform Resource Locator) to the Project Freewheel server. The URL identifies the location of a DWF file publicly available on the internet. Alternatively, the user can specify the path to a DWF file on a local or network hard drive.

2. The Project Freewheel server uses the internet to retrieve a copy of the DWF file onto the local hard drive of the server. Password protected DWF files, DWF files with digital rights management, or files in a location where a user name and password are required will not work (at this time).

3. To create Project Freewheel, we took the core rendering engine from the Autodesk Design Review and AutoCAD, tuned it for a web server, and repackaged it. Project Freewheel uses this rendering engine to convert the DWF file to a PNG (Portable Network Graphics) or JPEG (Joint Photographic Experts Group) image file.

4. The Project Freewheel server returns the image to the user's browser. Since image files can be viewed natively by browsers, no additional software is required. Nothing has to be installed on the user's machine. A low resolution image is returned for immediate viewing while a higher resolution image is generated and then returned.

5. As the user zooms, pans, or orbits, JavaScript on the user's computer makes requests to the Project Freewheel server for new image files. This is also possible without installing additional software since browsers support JavaScript. The Project Freewheel server applies the pan, zoom, or orbit to the DWF file, creates a new image file using the rendering engine, and returns the image file to the user's browser.

The ability to pan, zoom, and orbit DWF files free from installing software and independent of a particular platform allow users who: cannot install Autodesk Design Review, are running on Linux or the Macintosh, or are using a device such as a cell phone to view the design data with true fidelity.