### Author Topic: applying multiple forces to ridgid body  (Read 3611 times)

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#### Herra Tohtori

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##### Re: applying multiple forces to ridgid body
Other really fun things to consider:

-shockwaves - anything moving at trans-sonic speeds will already encounter Mach+1 airflow velocities at some points on their wings and fuselage, even if the indicated airspeed is less than Mach 1. Propeller blades are a good example of this; it's also the reason why helicopters are fundamentally limited to velocities lesser than Mach 0.5. Thankfully, FreeSpace doesn't have propellers... so propeller torque will not need be taken into account.

-compressibility

-buffeting

-vortices (induced drag/wing tip vortices/wake turbulence), and I'm not talking about the difficulty of modeling turbulent airflows. As an example, a very large portion of lift generated by the Concorde's wings is due to large stable vortices on top of the wings reducing the air pressure there. So lift is not exactly always just a function of angle of attack and airspeed in  laminar airflow...

-shifting of aerodynamic balance (center of pressure) in different velocities. For example Concorde dealt with this by shifting it's center of gravity accordingly by fuel transfers.

-stress factors depending on flight state; overspeed and pulling over-g's comes to mind first. You'll likely also want to implement blackouts and redouts somehow. For example, even if the ship itself can handle re-entry, it's unlikely that the pilot can handle the rapid deceleration if the ship were to, say, turn sideways or enter uncontrolled spin.

Have fun.
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#### Nuke

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##### Re: applying multiple forces to ridgid body
lots of things to model. right now im working on basic flight dynamics. seeing as this is an attempt at an aerospace engine, i will most likely need to consider transonic physics, otherwise it may be impossible to reach orbital velocity (not that you would have enough space without the ability to translate the entire scene, keeping the player in the "happy zone" of floating point math). i dont want the flight model to be too simple, but on the other hand i dont want to get too complicated.

ive given some thought to dealing with tail physics. my aoa computation also figures out the aoa of the tail, which is essentially a neutral airfoil with a Cl of 0. for every degree an airfoil is rotated in relation to oncoming wind (regardless of its level flight Cl), its Cl increases or decreases by about 0.11 (until the upper or lower stall angle is reached), so i should be getting a lateral lift force from the tail if i choose to simulate one. a control surface on that thail could also change the Cl. of course i dont want having a rudder be the only possible way to induce yaw, you could accomplish the same kind of motion by inducing drag or with a tail rotor for example.
« Last Edit: January 28, 2010, 05:32:55 pm by Nuke »
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#### Bobboau

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##### Re: applying multiple forces to ridgid body
you could recenter the 'happy zone' every time the player's center gets too far away from the origin.
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#### Nuke

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##### Re: applying multiple forces to ridgid body
that was the idea. something like that would best be implemented at engine level though. you would have to transform every object's position, and its old position so you dont screw up collision detection. of course then youd have to make sure this doesnt confuse the ai or weapons (missile homing position would change too so that would need to be translated) or cause artifacts in gauges and such. it doesnt take a stretch of the imagination to think of things it could potentially screw up. script doesn't (and shouldn't) have enough access to tie up all the loose ends. as it stands im gonna end up taking a good look at the engine physics anyway, in order to make physics more moddable. modularization would be a good start. once a translate scene function is implemented, then the scripting or events system should be able to use it. im sure there would be uses for this kinda thing other than physics.
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

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