.bullet and Dynamica

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stnal
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Joined: Wed Nov 10, 2010 8:57 am

.bullet and Dynamica

Post by stnal »

Hi all,

I'm new to Bullet and I need some help with it.
So far I've read the user manual and I also managed to compile and integrate it into the Ogre3D engine (using a wrapper).

I have a few question on some topics so I divided them into different threads...

1. I didn't understand why do I need the .bullet file, is it used just for saving precomputed complex physics shapes? or does it have an additional use?
2. I've read the Dynamica is used for physics special effects and it can save it's output to .bullet. Can you please give an example of what kind of special effects? Or what is the workflow of using it? In my wrapper it is possible to create a physics shape out of a mesh that was loaded to the graphic engine, so I want to figure out if I do need Dynamica?
3. Compiling Dynamica for 3DS max 64bit, anyone had a successful compilation/usage? for what it was used?

Thanks in advance,
Stan.
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Erwin Coumans
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Re: .bullet and Dynamica

Post by Erwin Coumans »

Using a modeler makes it easier to create and assign appropriate collision shapes and their types (box, sphere, capsule, cylinder, convex hull, concave triangle mesh), rather than automatically generation from the graphics mesh (always using triangle meshes is inefficient).

Also, it is useful to setup complex constraint systems, such as ragdolls etc.

Using cmake you should be able to compile a 64bit version of Dynamica. There is also a precompiled version for most versions here:http://bullet.googlecode.com/files/Dyna ... rsions.zip

Thanks,
Erwin
stnal
Posts: 7
Joined: Wed Nov 10, 2010 8:57 am

Re: .bullet and Dynamica

Post by stnal »

Thanks Erwin,

That's awesome... The binaries are precompiled for Maya and I need to 64bit version for 3ds max so I'll try to build it myself.
I just upgraded to version 2.77 for that and my code now is working with it.

Thanks,
Stan
stnal
Posts: 7
Joined: Wed Nov 10, 2010 8:57 am

Re: .bullet and Dynamica

Post by stnal »

I've compiled the 3ds-max plugin and successfully loaded it to 3ds-max 2011 x64 and it works for me,
I haven't tested the .bullet file generated yet (I followed the two spheres example in the manual).

I have a question though:

1. Is there a way to make an object "unphysical" ?
2. Objects are spawned dynamically in my game, can I still use a .bullet file for it?
3. What happens if I change the object's structure (deforming the mesh), how does it affect the "physical object"? do I need to make it physical all over again?
4. Is the 3ds max plugin different than MAYA? I'm really considering moving to MAYA for native support...

Thanks,
Stan
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Erwin Coumans
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Re: .bullet and Dynamica

Post by Erwin Coumans »

1. Is there a way to make an object "unphysical" ?
Set the mass to zero, or flag it as 'static'.
2. Objects are spawned dynamically in my game, can I still use a .bullet file for it?
For a simple shape such as a box or sphere, it is easier to programatically generate it, but for more complex structures you can use a .bullet file. There are various ways of getting this data and instantiating it later on (use a second/separate dynamics world, or load the .bullet file without adding objects to the world by modifying the btBulletWorldImporter.
3. What happens if I change the object's structure (deforming the mesh), how does it affect the "physical object"? do I need to make it physical all over again?
4. Is the 3ds max plugin different than MAYA? I'm really considering moving to MAYA for native support...
The 3ds Max plugin was just a quick port using the original PhysX plugin, and the Maya plugin has more features. Both plugins could use some attention to make them more mature, but but we haven't had the resources for this. Contributions are welcome.

Thanks,
Erwin
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