how to make enemy sprite shoot at player

Question

I'm using a sprite kit to create a game.

I have a player node which I control by touch but then I have an enemy node that moves on its own. I need the enemy to be able to shoot projectiles on its own. I'm guessing I would need a method for this and to call it. I need the direction of the projectiles to shoot wherever my player is. Any suggestions?

Here is the method I have:

  -(void)monstershoot
 {

SKSpriteNode * projectile = [SKSpriteNode spriteNodeWithImageNamed:@"projectile"];
projectile.position = _enemy.position;

CGPoint offset = rwSub(_player.position, projectile.position);

if (offset.x <= 0) return;

[_background addChild:projectile];

CGPoint direction = rwNormalize(offset);
CGPoint shootAmount = rwMult(direction, 1000);
CGPoint realDest = rwAdd(shootAmount, projectile.position);

// 9 - Create the actions
float velocity = 480.0/1.0;
float realMoveDuration = self.size.width / velocity;
SKAction * actionMove = [SKAction moveTo:realDest duration:realMoveDuration];
SKAction * actionMoveDone = [SKAction removeFromParent];
[projectile runAction:[SKAction sequence:@[actionMove, actionMoveDone]]];
}

But nothing happens when I call it.

there are no projectiles being shot by the enemy. the enemy is just there. the point was for them to shoot at my player. but "nothing happens" @CHBuckingham — ShariShar

robert robert · Accepted Answer · 2014-07-14T19:50:50

It will do "nothing" in two cases: the image doesn't exist or the enemy is right of the player. Replace this line

if (offset.x <= 0) return;

by a check if the length of the offset vector is 0. You could write a method to calculate the length by using

sqrtf(powf(offset.x,2) + powf(offset.y,2))

Further you should use the length of shootAmount to calculate

float realMoveDuration = 1000 / velocity;

which will give you the same (and correct) speed for every projectile. But otherwise I see nothing wrong with your code.

how to make enemy sprite shoot at player

1 Answers