Introduction

There are many different file formats to store any given content type. This is especially true in the case of 3D content, where it seems that nearly every vendor of 3D software tends to come up with their own unique file format. In our evaluation of a number of popular 3D software packages we have documented over 144 different file formats (McHenry et al., 2011). Having many different formats for the same type of data is a problem for a couple of reasons. The first reason is a matter of accessibility, in that having many formats makes it difficult to share data. If a particular format is obscure or used by only one particular software application, then content created in that application might be difficult to share with users who do not have that software. The second reason is a matter of preservation. If a software vendor uses a proprietary format and does not make the format's specification open, then if that vendor were ever to go out of business, any content stored within that format could be potentially locked away forever. This situation has been known to occur.

One might argue that in an ideal world there would only be one file format for each type of content. Having one format, a format that has a standardized open specification, would make archiving that content much easier, in that even if a viewer no longer exists in the future for that format, a new viewer could be created based on the available specification. Determining what this format could be is a problem. Even once this format is determined, converting from all the formats available today to that one format is also a problem.

As soon as the need for file format conversion arises we must begin to consider information loss. In Table 12.1 we list several 3D formats along the types of information they each support. While there are a variety of formats to store 3D content, each can store information a little differently.

As shown in the table, 3D files store a variety of attributes from geometry, to appearance, to scene properties and animation. Each attribute can also be stored in a number of ways. Not all file formats support all attributes. Converting between formats that do not support the same type of information will result in some sort of information loss.