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Physics System - ODE to Bullet?

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Physics System - ODE to Bullet?

Postby mal_CanDo » 28 Apr 2009, 16:54

I have just looked briefly into the physics capability of Shiva, and it seems to just support spherical and bounding box collisions for moving objects.

It also uses ODE ( http://www.ode.org/ ), which is a pretty OK open-source physics engine ( but doesn't seem to be getting many new updates in the last number of years ).


An alternative for the Shiva team might be to use Bullet ( http://www.bulletphysics.com ), another open-source physics engine. Bullet is very highly maintained, and is also available on iPhone as well as being cross-platform. It even supports some features that Shiva might want to support in the future ( soft body / cloth ), and I believe that the main developer had at one stage written an ODE to Bullet conversion layer.

It also has a wide range of configurable constraints, and even supports concave to concave collision detection.


One other advantage to a lot of people using Blender for modelling is that Bullet Physics has been incorporated within Blender ( both for the Game Engine, where it replaced ODE as the main physics engine, and also for pre-baking animations - although this currently uses the GE to perform the simulation at a high step / frequency ). This would mean that 3D artists could be able to test a physical setup in Blender before exporting to Shiva for final tweaking ( especially if constraints were involved )


If a Shiva developer reads this, definitely check out the Bullet website - I personally know the main developer ( Erwin ), and besides being a very cool and hard-working guy, he's keen to see the Bullet engine used in different applications ( btw Bullet physics even has a credit in Grand Theft Auto! )
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Re:Physics System - ODE to Bullet?

Postby NiCoX » 04 May 2009, 09:05

Hi mal_CanDo,

At the time we've choosen ODE, Bullet did not exist (or was in a very early stage of development). For the time being, it is true that ShiVa does not exploit 100% of the ODE's features, and we have to make lot of improvements for physics in general (expose more ODE's features and/or switch to Bullet and/or other(s) physics backend(s)), this is planned.

About ODE, its kernel is stable and flexible, the API is really user friendly (like Havok), and we know it well enough to add new features.

We are currently focusing on lot of other things for 1.8, and the major physics improvements will certainly come for 1.9.

:)
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Re:Physics System - ODE to Bullet?

Postby mal_CanDo » 06 May 2009, 04:59

Hi Nicox,

Thanks for the info.

With regards improving access to existing ODE features, hopefully being able to use dynamic convex rigid bodies, rather than just box / sphere, is high on the list for a fairly quick update.

As convex rigid bodies is already supported within ODE, is the issue with implementing it to do with the addition of the "shrink wrap" code to generate the convex hull?

Mal
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