[ODE] AI steering behaviors using ODE

[Raul Chaparro]

My problem is only about calculating torque from Force value, getting ship's 
heading
always with correct orientation. After that, i only must call functions like
dBodyAddTorque or dBodyAddRelTorque.

 <offtopic> no, de momento será un fps :) </offtopic>

----- Original Message ----- 
From: "STenyaK (Bruno Gonzalez)" <stenyak at gmx.net>
To: "Raul Chaparro" <raul.chaparro at pyrostudios.com>; <ode at q12.org>
Sent: Monday, May 15, 2006 10:34 PM
Subject: Re: [ODE] AI steering behaviors using ODE


> I'm not an expert in physics nor in maths, but assuming your force-related 
> code is right, and since torques are the equivalent to forces when it 
> comes to rotations, the code should be pretty similar: just replace 
> position with angle, velocity with rotational velocity, force with 
> torque... i think that should work.
>
> <offtopic>así que un juego de naves espaciales en 3d... será de 
> estrategia? O:-)</offtopic>
>
> On Mon, 15 May 2006 17:50:37 +0200, Raul Chaparro 
> <raul.chaparro at pyrostudios.com> wrote:
>
>> Hello. I'm new with ODE, just trying to use it to physics needed for a 
>> 3D spaceship game. I have a problem about calculating torque of enemy 
>> ships. Perhaps my question is more about physics than ODE, but i have 
>> this problem since many weeks ago, any help would be appreciated. Thanks.
>> The enemy spaceships moves with steering behavior forces. Once force is 
>> calculated, physics are updated and ship moves. The problem is that 
>> resulting force is applied linearly to the Center of Mass (translation). 
>> I don't know if it is possible obtain torque from this initial force, 
>> because there is no rotation at CM.
>>
>> Just now i'm not using rocket engines to get the propulsion of the 
>> ships. For example, to calculate force when ship is going towards an 
>> enemy, i do:
>>
>> current velocity = ship.velocity
>> desired velocity = target.position - ship.position
>> Force = desired velocity - current velocity
>>
>> I would need to find how to calculate torque based on that Force. If i 
>> imagine one engine thrust at the center bottom of the ship, applying
>>
>> Torque = (CM - point of force application) X Force         (X = cross 
>> product)
>>
>> then i obtain one torque vector that sometimes points in wrong 
>> direction, which makes ship's rotation faces away target and not towards 
>> target. I am trying that ship's heading always points to right direction 
>> while it moves. How can i solve that?
>>
>> Other solution I've thought is create many thrusters at backwards ship, 
>> all controlling torque and lineal force (for example one for each vertex 
>> of the bounding box backwards), or one controlling lineal force and the 
>> rest controlling only torque, but then, how to calculate the force to 
>> apply to each thruster based on Force value?
>>
>> Again, thanks for your time.
>> R.
>
>
>
> -- 
> Saludos,
>     STenyaK
>
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