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COLLADA vs FBX... Are They Worthwhile for Generic Model Formats?

Vincent_M · 2014-09-03T15:07:40

I'd like to use a more standardized model format that's a commonly-exported format across many 3D software production packages (Blender, Maya, 3DS Max, etc), and it seems that there are two: COLLADA and FBX. The problem is, it seems that there are multiple versions for these formats out there, and the exporters for each modeling package that supports these formats will provide the data in slightly different ways. Some even with missing features. It appears that the modeling package being used, the version of that package, the version of the supported exporter provided, and the file version are all variables that need to be considered. This is from what I've gathered so far, anyway. I understand that these formats are meant to be generic formats to hold all kinds of data that the engine can interpret, and use in an optimized way, but due to this, it seems like these formats change on a regular basis. I mean, it seems that there's really no standard exporter for COLLADA let alone a solid, multi-platform importer (it sounds like ASSIMP has done a good job, though). FBX seems to change every 6 months, which requires a new SDK with radically different APIs. ASSIMP seems really nice since it can grab models from a variety of different formats, and provides a common interface for working with the data once loaded. The problem with ASSIMP is that it doesn't handle FBX as well as I thought it would (since the specs change frequently, I'm guessing). From what I've seen, FBX is used quite a bit. Has anyone had any experiences related to handling COLLADA or FBX? If I could, I'd prefer to work with just FBX.

General and Gameplay Programming Programming

Started by Vincent_M August 30, 2014 11:19 PM

17 comments, last by Ed Welch 9 years, 7 months ago

Eric Lengyel

3,463

September 02, 2014 04:33 AM

These are just some of the reasons we created the Open Game Engine Exchange format (OpenGEX):

http://opengex.org/

When do you think you'll have an exporter ready for Blender? That's currently what I use since it's free, stable, highly-functional, and there are communities of artists out there with Blender models you can download for free. It'd be pretty easy to get a few models of Sintel with various animations to try different tests.

The Blender exporter is currently in development and should be available pretty soon.

I work on this stuff: Slug Library | C4 Engine | The 31st | Foundations of Game Engine Development | OpenGEX

Vincent_M

969

Author

September 02, 2014 04:57 PM

I'm excited to try it out. In the meantime, I setup the FBX SDK, and began exporting models from Blender (FBX 7.4). Surprisingly, the SDK with its constant API changes, still work. Btw, if I were to write a community-driven, open source, engine utilizing the FBX SDK, would I be able to distribute my engine? I understand that I wouldn't be able to distribute Autodesk's own SDK along with it, but if I were to distribute the built binaries on my end, would I have any issues there?

Btw Eric, I checked out your C4 Engine back in 2011, and it's impressive! It inspires me to become better at what I do.

frob

46,221

September 02, 2014 07:25 PM

We've used collada for just about everything for about six years or so, circa 2008.

Very versatile, and very steady standard. Especially considering there is a straightforward ISO standard for the format you can know what to expect. Anything that doesn't conform to the standard is a bug.

For final builds we transform the data into a format that loads directly into memory, but as an intermediate state the dae files are nice for everything. As they are XML you can even diff the files to some extent and easily manipulate them in code if necessary with common and standard libraries for various languages.

Hodgman

52,717

September 02, 2014 09:47 PM

Especially considering there is a straightforward ISO standard for the format you can know what to expect. Anything that doesn't conform to the standard is a bug.

What do you do when you come across these bugs? Report them to Autodesk and then hold your breath for 5 years? :D :lol:

. 22 Racing Series .

Ed Welch

1,013

September 02, 2014 11:20 PM

These are just some of the reasons we created the Open Game Engine Exchange format (OpenGEX):

http://opengex.org/

Interesting. Can you save the file as binary? That would be an important feature.

Hodgman

52,717

September 02, 2014 11:33 PM

These are just some of the reasons we created the Open Game Engine Exchange format (OpenGEX):
http://opengex.org/
Interesting. Can you save the file as binary? That would be an important feature.

For an interchange format it's not really that important -- games don't use Collada/FBX/ogex files directly, so they don't have to be optimized for loading. You should always convert from your interchange formats to a binary format that's optimal for your specific engine.

It might be interesting for OpenGEX to additionally define a game-ready binary format that's useful for 90% of devs though :)

When I started using Collada I was worried about simple 1MB models being stored as 60MB of text/xml... But it seems to work fine as all the decent repository systems compress text files before storage/sync anyway.

. 22 Racing Series .

frob

46,221

September 03, 2014 01:25 AM

Especially considering there is a straightforward ISO standard for the format you can know what to expect. Anything that doesn't conform to the standard is a bug.
What do you do when you come across these bugs? Report them to Autodesk and then hold your breath for 5 years? :D :lol:

Currently using OpenCollada plugins for import/export into Maya. If we can't fix it or don't want to, just report them to the community.

Eric Lengyel

3,463

September 03, 2014 03:42 AM

We've used collada for just about everything for about six years or so, circa 2008.

Very versatile, and very steady standard. Especially considering there is a straightforward ISO standard for the format you can know what to expect. Anything that doesn't conform to the standard is a bug.

Unfortunately, the reality is that most Collada exporters don't follow the standard, so you can't know what to expect a lot of the time. We had been using Collada exclusively since 2005, but the problems had become so bad that the C4 community decided that they needed something more reliable. (And no, FBX is not better.) I wouldn't have spent so much time developing OpenGEX if Collada worked. In general, Collada is unstable (e.g., the right way to do things changed drastically from one version to the next), over-engineered (e.g., too much abstraction with things like accessors), and under-documented (e.g., ask almost anyone what the proper way to interpolate Bezier keyframes in Collada is, and they won't be able to get it right even if they've read the latest spec from cover to cover). I personally find that the data in a Collada file also isn't organized very well, but other people may not have a problem with that.

I work on this stuff: Slug Library | C4 Engine | The 31st | Foundations of Game Engine Development | OpenGEX

Eric Lengyel

3,463

September 03, 2014 03:48 AM

Btw Eric, I checked out your C4 Engine back in 2011, and it's impressive! It inspires me to become better at what I do.

Thanks! Version 4.0 is coming out soon, and it's a huge update, a bigger step forward than we've ever released before.

I work on this stuff: Slug Library | C4 Engine | The 31st | Foundations of Game Engine Development | OpenGEX

Ed Welch

1,013

September 03, 2014 03:07 PM

These are just some of the reasons we created the Open Game Engine Exchange format (OpenGEX):
http://opengex.org/

Interesting. Can you save the file as binary? That would be an important feature.
For an interchange format it's not really that important -- games don't use Collada/FBX/ogex files directly, so they don't have to be optimized for loading. You should always convert from your interchange formats to a binary format that's optimal for your specific engine.

It might be interesting for OpenGEX to additionally define a game-ready binary format that's useful for 90% of devs though

When I started using Collada I was worried about simple 1MB models being stored as 60MB of text/xml... But it seems to work fine as all the decent repository systems compress text files before storage/sync anyway.

It slows down the art pipeline. At critical parts of the project your going to be exporting huge scene into your world editor, maybe 100's of times a day.

COLLADA vs FBX... Are They Worthwhile for Generic Model Formats?

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COLLADA vs FBX... Are They Worthwhile for Generic Model Formats?

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