[ODE] C# Access

[Hutchison, Ben]

John,

I'd be interested to see an interface to ODE from C# so please make your
work available.

Im not sure if you're aware of Axiom
(http://axiomengine.sourceforge.net/), who claim to be writing a physics
engine layer for their C# game engine based on ODE. They may have
grappled with the integration issues already.

I know that the MS .NET tools include a feature (the "/clr" switch) that
allows normal, unmodified C++ code to compile to IL byte-code, that can
be executed within the .NET runtime (as opposed to making native<->CLR
calls). So, it may be possible to recompile ODE as is into .NET IL code,
rather than calling it as a native library. This area is still in some
flux, undergoing a name change from "managed C++ extensions" to C++/CLI,
and some beautification of syntax. Just an option to consider.

Another issue you may/may not have hit is the relocation of objects in
the CLR due to garbage collection. Pointers from native to CLR objects
are invalidated when such relocation occurs. 2 solutions are the "pin"
keyword, which prevents relocation, or better, the "gcroot" object
handle containing a smart pointer that's kept up-to-date when the system
moves its target object.

Re: the "__stdcall" issue when directly calling back from native code, I
haven't seen any way that can be changed short of a Managed C++
intermediator. (Useful:
http://www.mail-archive.com/advanced-dotnet@discuss.develop.com/msg04498
.html)

Regards
Ben Hutchison

> -----Original Message-----
> From: ode-bounces at q12.org [mailto:ode-bounces at q12.org] On Behalf Of
John
> Buehler
> Sent: Thursday, 23 September 2004 7:27 AM
> To: ode at q12.org
> Subject: [ODE] C# Access
>
> I've created a C# interface to ODE so that I can use the derned thing.
> All
> I've done is the absolute minimum to permit a C# application to make
calls
> to ODE according to the existing documentation.  I made no attempt at
> trying
> to abstract the functionality, as was done with the C++ wrapper in the
> contrib area.
>
> I'll be perfectly happy to pop what I have into the contrib area or
turn
> it
> over to someone else to play with, but the catch is that in order to
get
> collision detection working, I had to alter the dNearCallback
definition
> within ODE to include __stdcall.  I'm running the 2002 .NET stuff
(2003 is
> on order) and it apparently doesn't tolerate other calling
conventions.  I
> have no idea if later .NET releases have a workaround.
>
> The C# stuff that I have is largely untested in that I've only called
a
> couple dozen functions so far.  But the creation of the interface
class
> was
> very straightforward, so any problems should be limited to typos.  I
> suppose
> the one caveat would be that I haven't fooled with any of the ODE
> functions
> that return callbacks.  I assume .NET can handle marshalling that, but
I
> don't really know.
>
> I'm interested in comments in two areas:
>
> 1. Is this C# interface class something that should be pushed into
> contrib?
>
> 2. Is there another means of getting callbacks to work with .NET other
> than
> by making the ODE type include __stdcall?  If not, can the ODE
> distribution
> include __stdcall on callbacks for Windows builds?
>
> I modified and ran with a debug build of the 12-Jul-2004 ODE sources
at
> single precision.
>
> JB
>
>
> _______________________________________________
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> ODE at q12.org
> http://q12.org/mailman/listinfo/ode

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