Quick and Dirty Heat Seeking Missiles...

BarkBarkCo

Here is a game I'm messing with that is in the very early stages...

I liked the result of the heat seeking missiles logic I added so much, I thought I'd share the joy!

http://gamesalad.com/game/play/56585

quantumsheep

Can't see it at work, but looking forward to trying it out tonight

Heat seekers are my favourite weapons of choice :P

beefy_clyro

Likewise QS, defo looking forward to trying it out ... damn windows at work!

firemaplegames

Nice demo!! I will have to check out how you did that!

quantumsheep

firemaplegames said:
Nice demo!! I will have to check out how you did that!

It's as if he enjoys torturing us!

beefy_clyro

yeh right. talk about rubbing it in! is it half 5 yet?

BarkBarkCo

@firemaplegames, Thanks for the kind words!

It's real simple ... and kinda dirty.

There is no live tracking of the falling bombs. They are set to fall at a random x position, at set intervals. About .5 seconds into there existence, I mark their current X position in a game (real) attrib, `game.LastBombX`. Then, when missiles are spawned, I have them interpolate their own x position over a 1~ second period to `game.LastBombX`. That is what makes them look like they are "thinking" ...

I'm in the theoretical stages on a method that will allow me to always track the bomb with the lowest `self.position.y` ... but that is yet to be added.

quantumsheep

Ooh! Sounds interesting!

I've also used interpolate to make 'Enemy' homing missiles that track the player.

In your method, are you changing the last bomb value to the individual bombs position? So if two bombs spawned, for .5 seconds bomb1 would have the value 'last bomb' until bomb 2 spawned and it would switch to that?

BAH! Won't get home for another 2 hours or so and I'm gagging to see how this works...

QS

BarkBarkCo

Only one bomb is spawned at a time, in .5 second intervals (I think..I'm also on a PC right now). I'm only logging the x position of a bomb, .5 seconds into its life cycle; under the assumption that the bomb and missile will intersect in flight. Each new bomb overwrites the logged x position, so only one bomb is tracked at a time. That allows for some misses that I hope to clear up soon with logic that only tracks the bomb that has fallen the most in the scene.

That said, if you fire at a rate greater than 1 missile per .5 seconds, at least one missile would track every bomb.

beefy_clyro

nice

Eastbound

Oh wow I had always marked heatseaking for the player off because I thought it was too complicated without really thinking about it.

Thanks for the epiphany!

Yeah you could simply have every enemy check if their position x and y are closer to the player's than the global variables for closest_e_x and closest_e_y and change closest_e_x and y if they are.

I'm afraid this would be a little too heavy for an iPhone shooter (every enemy would have to check and perhaps change variables with every tick of the game's clock), but I think it would work fine on iPad, and maybe even the newer phones (never tested on 3Gs).

jmp909

hi,

not looked at your example yet (no mac here) but I found this really nice heat seeking flash example (with source), with modifiable parameters for turn speed etc.

i've pasted the main function below....if you altered it to use game variables eg followerMoveX, targetX etc should be adaptable with constrains. (note vectorToAngle = atan2)

http://www.freeactionscript.com/2008/12/game-weapons-heat-seeking-missiles-rockets-torpedoes/

`

function doFollow(follower, target):Void

{

//get distance between follower and target

follower.distanceX = target._x - follower._x;

follower.distanceY = target._y - follower._y;

//get total distance as one number

follower.distanceTotal = Math.sqrt(follower.distanceX * follower.distanceX + follower.distanceY * follower.distanceY);

//calculate how much to move

follower.moveDistanceX = turnRate * follower.distanceX / follower.distanceTotal;

follower.moveDistanceY = turnRate * follower.distanceY / follower.distanceTotal;

//increase current speed

follower.moveX += follower.moveDistanceX;

follower.moveY += follower.moveDistanceY;

//get total move distance

follower.totalmove = Math.sqrt(follower.moveX * follower.moveX + follower.moveY * follower.moveY);

//apply easing

follower.moveX = missileSpeed*follower.moveX/follower.totalmove;

follower.moveY = missileSpeed*follower.moveY/follower.totalmove;

//move follower

follower._x += follower.moveX;

follower._y += follower.moveY;

//rotate follower toward target

follower._rotation = 180 * Math.atan2(follower.moveY, follower.moveX)/Math.PI;

}

`

jmp909

i have posted this here
http://gamesalad.com/forums/topic.php?id=7197#post-47531

but have issues.