Jump to content
• Advertisement

# Calculating forces, speed,acceleration of a plane

This topic is 2342 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

## Recommended Posts

I am trying to make the plane fly by calculating forces of thrust gravity drag and lift (but now i am only using now two forces: gravity and thrust)

nvm because i dont have a lift force because of Cl = 2 * pi * attack angle = 0.0ff

the stupidiest thing now i see that: my plane always goes down towards gravity vector even when thrust force is 2 times greater than gravity force and acts in the opposite direction

second issue is that: i cant calculate proper normalized vector (normalized gravity force vector)
in example: i have plane pos: x=50 000 m y = 100 m z = 30 000 m and the normalized vector is something like this: x = 0.7; y = 1.5, z= 0.4; and i donkt know why the y is fck-ing 1.5 here

i always get this effect (lol clouds are 320 km away form the surface - and we are in south america )
[media]
[/media]

i use these equations:
F=m*a
s=v*t
s= v0*t+a*t*t*0.5

i start the simulation with this:

MODEL->t = GetTickCount();
MODEL->pos = position;
MODEL->old = position;

 void __fastcall TVehicle::ProcessFrame() { int p = GetTickCount(); float x = abs(float(p-t))/1000.0f; if (x <=0 ) return; t3dpoint kk; kk = YPRangle.rf; //thrust force orientation float Front_force = Throttle_to_force( Throttle ); //thrust force val float Q = eGForce * mass; // gravity force val t3dpoint TForce_vec; t3dpoint GForce_vec; TForce_vec = YPRangle.rf; //thrust force direction (movement) t3dpoint c; c = vectorAB(pos, zero);//center of earth GForce_vec = Normalize( c ); //g force direction //density float drag_force = 0.350*pressure*(V*V/2.0f); GForce_vec = vector_multiple(GForce_vec, Q); TForce_vec = vector_multiple(TForce_vec, Front_force); t3dpoint ALL_FORCES = vectors_add(GForce_vec, TForce_vec);//add forces //Cl = 2 * pi * pitch angle (in radians) //L = .5 * Cl * air_density * V^2 * A t3dpoint VA; //acceleration vector VA = ALL_FORCES / mass; // a = F / m float dk = ( x*x ) / 2.0f; VA = VA * dk; //(a * t^2 )/ 2 float h = V*x; VA = VA + h; //V0*t + (a * t^2 )/ 2 //s = V0*t + (a * t^2 )/ 2 pos = vectors_add(pos,VA ); t = GetTickCount(); V = n3ddistance(pos,old) / x; // s = V / t so calculate velocity old = pos; } 

what am i doing wrong ?

now wypadkowa is ALL_FORCES :] no its not irricht its mine engine

#### Share this post

##### Share on other sites
Advertisement
I would certainly start with getting rid of GetTickCount() in this kind of use. Resolution of this function is somewhere between 10 and 20 ms, which absolutely isn't enough even for applications running at mere 60 FPS. Try QueryPerformanceCounter() instead.

I didn't have much time to dive into your code, I just noticed that it's quite chaotic and confusing. You should give better names to your variables. For example your "x" is usually called "dt", or "delta_time".
X should be strictly reserved for coordinates.

And short names like VA, h, V, dk tell nothing about their meaning, especially when for example "h" doesn't mean "height".

#### Share this post

##### Share on other sites
never mind i was adding translation vector to float ( but i should add vector to vector )

and the GetTickCount() has resolution such as 1 ms not 10 ms

#### Share this post

##### Share on other sites
Hidden
The OP says he has figured out the answer. So this thread is closed.

#### Share this post

##### Link to post

and the GetTickCount() has resolution such as 1 ms not 10 ms

Nope, it doesn't.
It seems to have a 1 ms resolution, because it returns a DWORD value in miliseconds. But if you test it better, you'll notice that when for example you are calling the function repeatedly, it may return something like
5411
5411
5411
5411
5411
5425
5425
5425
etc.

In fact, you won't get two succeeding values with difference of 1 ms, it will be returning the same value and after some time the value will suddenly increase in a step.

This limited resolution is mentioned also in the official documentation
http://msdn.microsof...v=vs.85%29.aspx

#### Share this post

##### Share on other sites

• Advertisement
• Advertisement

• ### Popular Contributors

1. 1
2. 2
Rutin
19
3. 3
4. 4
5. 5
• Advertisement

• 14
• 30
• 13
• 11
• 11
• ### Forum Statistics

• Total Topics
631781
• Total Posts
3002315
×

## Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!