Raydium 3D Game Engine

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PostPosted: Sat Jul 21, 2007 5:40 pm 
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When i was making a simple plane simulator i have notice a problem with ODE/Raydium: It has no air friction.

Imagine the next sequence:
You have a terrain, and a plane appears at a certain height, say 50 meters.
We can apply a force equal to gravity to maintaing the plane floating in the air, cause Gravity - Counte_rgravity_force=0, so the plane can float.

Now we can add one force directed forward to propulse the plane forwarding.
According the design of the planes, at high velocity, the plane moves up. So we can vary the countergravity_force depending on how much velocity the plane has.

At this point we have a plane that float and that can move forward, moving also up and down, according the velocity.

Now the problem comes:
We can add a new motor, to allow the plane turn left or right. We can position this motor in the (0,0,0) of the object or in the rear part (more realistic). In both cases we can experimentally notice that: THE PLANE DRIFT IN THE AIR!!!

This behaviour would be correct if the plane were an spacial ship, and the terrain were the space, with the earth in the distance. But is not right for normal planes.

At this point i'm not sure about: Is a raydium lack/fault? Is an ODE lack/fault? Is a programmer(me) lack/fault?
In other words: Should Raydium have a RAYDIUM_ODE_AIR_FRICTION parameter?


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 Post subject: flight simulator
PostPosted: Thu Aug 02, 2007 12:19 pm 
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Joined: Sun Oct 09, 2005 10:46 pm
Posts: 759
Hello,

Student work on a drone simulator:

Here is feed back information (in the wiki)
http://wiki.raydium.org/wiki/LpIer2007

There are information about plane model in pages.
I'll can send you the code if you are interested.

To simplify:

You need propulse, rocket like motor, directed in the direction of the plane.
The up force if proportionnal to this speed, and affected by yaw, pitch and roll of the plane.

Other command add torque to Y and Z axis of the plane.

If you want something more precise i can ask to a good "aeromodeler" en september.

Have a nice day.
Ouille


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 Post subject:
PostPosted: Thu Aug 02, 2007 12:32 pm 
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Nice!!!, i go to take it a try. And i'd appreciate a lot if you send me the code.
If i have a break this holydays, i'll try an spanish or english translation.

But i have a main doubt. Have you implemented air friction or just used aproximated ecuations to achieve the "right" movement of the plane?


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 Post subject: Bad and good news
PostPosted: Thu Aug 02, 2007 12:41 pm 
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Joined: Sun Oct 09, 2005 10:46 pm
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Hello,

I have nothing here at least for code. Y'll have to wait until september ;o(

But i'll send you the overall code.

AeroDynamic problems where driven by a friend with quite very good knowledge.
Equation where approximated to avoid to long compute time. But seem to be quite accurate at least as other flight simulators.

Plane modeling is accurate.

air fircition is integrated in the "trainée" the curve is linearized but not so far from reality.

For further information i'll invite him to this list if needed.

Have a nice day
Ouille


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 Post subject:
PostPosted: Thu Aug 02, 2007 2:12 pm 
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Ok, we'll wait until September. And i'll continue doing my test with just raydium forces.
Thanks


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 Post subject:
PostPosted: Thu Aug 02, 2007 10:04 pm 
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Joined: Sun Oct 09, 2005 10:46 pm
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hello,

Send your code, if i have some time i'll try to have a look.

Have a nice day

Ouille


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