A fast, easy to use, free, and community supported 2D game engine
Gray Olson
Member
Hi all,
In my game, I want to be able to move a tank around by rotating the device, which I can do and have optimized, the problem is shooting a bullet from where the tank is to the spot where the user touches. I am currently using CCMoveTo, but I have failed to make the correct algorithm that calculates what the duration should be, so that the bullet always moves at a constant pace, no matter if you touch it far away from the tank or close to it.
Thanks in advance,
Gray
criter88
Member
Try ray's blog he has a full game that shows you how to shoot and turn the sprite to face the point it shoots.
http://www.raywenderlich.com/352/how-to-make-a-simple-iphone-game-with-cocos2d-tutorial
jonathan0382
Member
Do this:
1. decide on how fast you want your bullet to move (in pixels per second),
2. determine the distance (in pixels) between the turret and the point touched (used pythagorus' theorem),
3. then use time = distance / speed to get the duration for the CCMoveTo action.
hth
jonathan0382
Gray Olson
Member
heres my touch method code:
-(void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [[event allTouches] anyObject];
CGPoint location = [touch locationInView:touch.view];
location = [[CCDirector sharedDirector] convertToGL:location];
//setup initial location of bullet
CCSprite *bullet = [CCSprite spriteWithFile:@"bullet.png"
rect:CGRectMake(0, 0, 10, 10)];
bullet.position = ccp(_tankGood.x + 15.0, _tankGood.y);
int offX = location.x - _tankGood.x;
int offY = location.x - _tankGood.y;
[self addChild:bullet];
float length = sqrtf((offX*offX)+(offY*offY));
velocity = 480/2;
float realMoveDuration = length/velocity;
[bullet runAction:[CCSequence actions:
[CCMoveTo actionWithDuration:realMoveDuration position:location],
[CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)],
nil]];
bullet.tag = 2;
[_bullets addObject:bullet];
}and my moving code (not sure if relevant):
-(void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
_tankBodyGood.position = _tankGood;
_tankTurretGood.position = _tankGood;
_tankLeftBoundry = _tankBodyGood.position.x - 20.0;
_tankRightBoundry = _tankBodyGood.position.x + 20.0;
_tankTopBoundry = _tankBodyGood.position.y + 20.0;
_tankBottomBoudry = _tankBodyGood.position.y - 20.0;
if (acceleration.x < 0.0 && _tankBottomBoudry > 0.0) {
_tankGood = CGPointMake(_tankGood.x, _tankGood.y + (acceleration.x * kTGS));
}
if (acceleration.x > 0.0 && _tankTopBoundry < _winSize.height) {
_tankGood = CGPointMake(_tankGood.x, _tankGood.y + (acceleration.x * kTGS));
}
if (acceleration.y < 0.0 && _tankRightBoundry < _winSize.width) {
_tankGood = CGPointMake(_tankGood.x - (acceleration.y * kTGS), _tankGood.y);
}
if (acceleration.y > 0.0 && _tankLeftBoundry > 0.0) {
_tankGood = CGPointMake(_tankGood.x - (acceleration.y * kTGS), _tankGood.y);
}
}
Mark Sawicki
Member
@termhn,
int offX = location.x - _tankGood.x;
int offY = location.x - _tankGood.y; // should be location.y ?i think your offY should be location.y - _tankGood.y;
As a side note, i think ccpDistance should work for you .. to calculate the distance between two points. Look in CGPointExtension.m.
-Mark
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