Physics Simulation Forum

Hi.
I have a question about physics APIs.

Havok has any tool to create physical scene interactively like world editor?
I cannot enough information about it in the official Havok homepage.
How's about Bullet and PhysX?

Thanks in advance.

Maya
The Nima COLLADA plugins for Maya can export COLLADA Physics .dae files, that can be imported into Bullet and PhysX.
Download latest Nima 1.02 for Maya 8.5, requiring Ageia PhysX 2.7.0 drivers installed here:
http://www.bulletphysics.com/ftp/pub/te ... x2_7_0.exe
This Nima 1.02 installer comes with partial source code.

If you want full source code to rebuild Nima, there is an older Nima 1.0 Beta 5 physics plugin for Maya with Visual Studio projectfiles/solution. This seems to be compatible with most Maya versions, up to 8.x. See the older Nima 1.0 Beta 5 documentation here:
http://bulletphysics.com/ftp/pub/test/i ... tation.pdf
http://bulletphysics.com/ftp/pub/test/i ... n_prev.doc
It would be great if someone can take this Nima plugin and add Bullet physics support.

3ds Max
Check out this free and open source physics plugin maintained by Ageia: http://sourceforge.net/project/showfile ... _id=191256

Blender 3D modeler has built-in Bullet simulation and physics modeling/COLLADA export.
Check out Bullet ColladaDemo and Extras/BulletColladaConverter how to import those files.

Other stand-alone editors include Scythe physics editor. Not sure about the physics export capabilities of tools like Hammer (Half Life), Worldcraft, Radiant (idSoftware), UnrealEd (Epic Games) or the Sandbox editor for Crytek's Crysis.

Hope this helps,
Erwin

I was about to ask a similar question. Thanks, Erwin!

Specifically, I'm looking at a way to author ragdolls, including joint limits (hinge and cone/twist), without reinventing the wheel.

We're using Maya, so I'll check out Nima.

I'm looking at Scythe as well. Looks interesting, but it seems a little... quiet over there. (3 months or so since the last update or post.) Erwin, I noticed your request(s) for Scythe to support COLLADA - know of any activity on that front?

Cheers,
Eddy

PS/FYI. Having worked with Havok ("Complete"), I can say that it has a decent tool-chain for this sort of thing (ie. ragdoll/world authoring) in the form of plugins for 3dsMax and Maya and a proprietary export file format. Anyone know if PhysX has anything similar?

Ageia PhysX is/was the driving force behind Maya Nima plugin, and Max-physx plugin, both are open source, but public development by FeelingSoftware/Ageia has stopped. So if we want publically available physics tools, we can continue from the last available public source repositories that are available. We need to be very pragmatic if we want results, that that developers can continue the projects. For example, to get Nima Maya physics plugin up and running again:

• Add the source code to a source repository, and add some active developers
• Replace FCollada by COLLADA-DOM, so that we have full round-trip (load and save data without loss of data, compliant to the specification)
• Replace PhysX by Bullet (even just to avoid requirement of installing PhysX drivers)

COLLADA Physics format is a very good intermediate file format to support/allow collaboration between different efforts. Without it, we keep on having small fragmented efforts.
Furthermore, consider this:

Commercial SDK agnostic:
The Maya, Max, Blender and standalone physics tools should work with Havok public version (to be released in May), Ageia PhysX and Bullet at least.

Packaging:
Once we have some useful version, we could try to make the plugins available through Khronos/COLLADA website. But in the meanwhile, Sourceforge or GoogleCode should do fine.


There are some source code snippets for a Scythe COLLADA support using COLLADA-DOM, but that is quite out-dated now. Apart from that, Adrian Boeing posted recently about a Scythe improvement, that adds COLLADA support through his PAL physics abstraction layer. Adrian, is there a website and public repository with your modifications on this Scythe standalone physics editor?

Thanks,
Erwin

Is anyone from Autodesk actively involved in the Collada initiatives?

I think it is necessary to have full devotion from them to get a serious workflow for collada graphics and physics.

What's the overall view of Collada in terms of business development? Does collada ever compete with some other interests, for example does anyone see a risk in the ease of walking freely between e.g. Max, Maya, Blender and Softimage - or to easily compare 4-5 physics engines, or correspondingly for graphics engines?

Are there any serious workflow examples with collada, i.e. an example where an entire game or simulator is defined almost entirely in collada (of course with the obvious limitations in e.g. procedurally controlled behaviour)?

Even though Autodesk might participate in Khronos and COLLADA, they are also involved in the proprietary Havok 'Reactor' plugin for Max. The Autodesk Maya build-in rigid body dynamics engine and tools haven't been updated for a long while. But they might develop some new proprietary technology, based on Jos Stam unified Nucleus physics work. It would be nice if the Nucleus Maya tools would allow to export physics information to fully open standard like COLLADA.

Reactor exports to a proprietary file format, and a lot of the Autodesk efforts use the the proprietary FBX file format, also promoted by Microsoft.

See the statement by Marcus Barnes, one of the COLLADA architects (formerly at Sony, now at Intel), at the SIGGRAPH 2007 panel:


Now that Havok is owned by Intel, and Ageia PhysX is owned by NVidia, hopefully it will help standardization.

Several big game companies have used COLLADA in their projects (out of the top of my head, Epic Games, Electronic Arts (The Sims), and Crytek). None of them used the physics features in COLLADA yet, so we need to evangelize and work on this new feature more.

Now we have dealt with the politics, it would be best to continue the technical discussion, so that we get some viable physics tools and plugins, fully open source and based on open standards
Erwin

Well, I "spent a little time" with Scythe and NIMA.

Scythe: While I found some aspects of the tool to be great (particularly the automated ragdoll creation and constraint limit visualization), I found the interface to be tricky to use (picking difficulties, and no way to name/identify your rigid bodies). Also, I'm not using Ogre - it seems Scythe only supports .mesh files (or its own .phs format) for import; so the extra dependencies (PAL might be great, but it's yet another ingredient to add to our tools) and workflow-steps are shying me away from this option. But, for those using Ogre, a little coding might go a long way to get this tool to meet your needs...

NIMA: I'm using Maya 8.5, and couldn't load the built plugin. I downloaded the source, hacked at it a bit (commenting some deprecated PhysX cloth, fluid and visualisation stuff), and managed to get it running in Maya. I was able to create/simulate boxes and capsules, but not convex-meshes (silent failure in the physics shape computation code). I haven't gone much further than that yet... but it looks like a fair bit of work to port this to the latest PhysX. The existing GUI framework could be a useful starting point for porting to Bullet, but I don't have the time to dedicate to this as a solo effort, nor am I familiar with MAYA.

So... (much as I hate to say it,) given my needs/timeframe, unless there's a unified movement on this front coming soon, I'm leaning towards building a basic ragdoll editor on top of our in-house toolset. That said, I'm willing to help with a global, long term solution that we (ie. my company) can switch to someday.

Any other efforts or motivation out there?

Cheers,
Eddy

Thanks for the evaluation.

The Maya Nima plugin is most promising, but it is indeed some work. If we are lucky, some students could pick up the project, perhaps as a Google Summer of Code project?

viewtopic.php?f=9&t=1960

I will check if there is any other way we can get some resources to get freely available physics authoring tools.
Thanks,
Erwin

Thanks Erwin.

A thought: although I'm not familiar with Blender, I'm wondering if it isn't a better (and perhaps easier) choice given it's existing integration of Bullet and the fact that it's free/open-source. Not everyone has Maya...

What do you think?
Eddy

Ageia open sourced the latest Nima plugin here:

http://sourceforge.net/projects/nimaplugin/

Not sure how it compares to the one available a while back,
Erwin