Projectile From A to B

[gamecreator]

Hi there. I'm making a simpler version of Worms and I need code (C preferred) to get a projectile from X1, Y1 to X2, Y2 but I'm horrible with math. But it gets a bit more complicated than that. Depending on the situation, there may not be enough velocity to hit the target. So the problem is, given V, is there an angle that exists that will hit the target. If so, what is it (I think there may be two so I would need the steeper of the two).

 

I think this may be the formula I'm looking for (from the wiki):

 

 

Also, if I understand it right, that assumes X1, Y1 is at 0, 0 so I think that needs to be subtracted from (added to??) the target.

 

Any help would be appreciated.

[Canardia]

You don't need math with LE. Just use a pivot and do a PointEntity(pivot,target), then you can read the pivot's direction using EntityRotation().

[Pixel Perfect]

If I understand this correctly he's not asking for the angle to the target as a straight line, which is what your suggestion would give but rather the vertical angle the projectile would need to be fired at given an x,y target position and a velocity to ensure the projectile hits it. Presumably this is a parabola flight path.

[gamecreator]

Thank you Metatron but yes, Pixel is right. I'm looking for code that would calculate the steepest angle that would fire something like this (over hills):

 

float getangle(float x1, float y1, float x2, float y2, float velocity)
{
    float angle;

    ...  ?

    return angle;
}

[Canardia]

I would use physics for that. That's what made Angry Birds famous too There's incredibly little physics based games on the market, and they will have huge success if made well.

[Scott Richmond]

No I believe he will be using physics but I think he's currently programming the AI so it knows what angle and velocity to shoot the projectile at to hit the target.

 

Gamecreator - To answer your question regarding the (x,y) I believe that they are relative variables. That is to say that the position of A is relative to that of B. So:

x = targetA.x - targetB.x // That'll get the meters between the launch site and the target

y = targetA.y - targetB.y // That'll get hte height of the launch site relative to the target

 

You'll have to mess around with the order of subtraction there I'm guessing, so you don't get any negative values.

 

Do you know how you're going to solve whether it will hit geometry or not?

[gamecreator]

Scott, I have collision detection taken care of with EntityCollisionCallback, so I'm set there. Right now my computers are just shooting randomly but I'd love for them to not be so aimless (ha ha).

[Scott Richmond]

Right well that equation should get you that, but it won't tell you whether it'll reach its target. You'll need to test each angle and velocity with a collision check to find one that won't hit geometry.

[gamecreator]

The good thing is that there are second chances. The computer, like the player, is allowed to miss. But if the projectile doesn't hit, it would be because the shot can't be made (because there won't be any wind or overhead obstructions). In that case, the computer will need to switch to a different target. Or a bigger weapon.

[Josh]

Looks like a calculus problem.

[Naughty Alien]

http://www.xinventions.com/main/spud/motion_equ.htm

or

http://zonalandeducation.com/mstm/physics/mechanics/curvedMotion/projectileMotion/generalSolution/generalSolution.html

or

http://www.pha.jhu.edu/~broholm/l5/node3.html

 

pretty much straight forward..

[Flexman]

Angry Birds gets mentioned a lot and while yes it's a simple physics game, its success (and they made 50 games prior to that) is the huge effort and experience applied to presentation then giving it away to create it as a brand.

 

 

For ballistics see this for a quick simple example of what you want.

 

http://warpycode.wordpress.com/2009/10/10/aiming-a-projectile-uphill/

[Road Kill Kenny]

Haven't had a look at those sites that NA posted but this is what I came up off the top of my head.

 

Its basically calculus and Newton's law F=MA or rather F=MU for instantaneous speed (U initial velocity)

 

Apologies that this is hand written. I have simplified the calculus part by using pre-determined physics acceleration equations. Hope you find it useful.

 

using these equations you should be able to determine the force required for a given mass and the angle to apply the force at. good luck

 

some definitions:

s- distance (m)

v- final velocity (m/s)

u- initial velocity (m/s)

a- acceleration (m/s2)

t - time (s)

 

[gamecreator]

Thank you all very much, especially Ken for the generous contribution. That gives me a lot to look through and try to implement when I have a little time.