applyImpulse towards CGPoint SpriteKit

Question

I'm kind of a newb in SpriteKit, game dev, as a matter of fact I'm just learning. So I got to a point where I what to move a bunch of nodes towards a users tap location. So far I fought that I might calculate a virtual right triangle and get sin and cos of angles based on the sides. Unfortunately that left me with a very strong impulse that doesn't really consider the user tap location.

Any ideas?

Thanks in advance.

Answer 1

Look up the shooting projectiles section in the tutorial by Ray Wenderlich here:

http://www.raywenderlich.com/42699/spritekit-tutorial-for-beginners

Change the code from the tutorial as follows:

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    // 1 - Choose one of the touches to work with
    UITouch * touch = [touches anyObject];
    CGPoint location = [touch locationInNode:self];

    // 2 - Set up initial location of projectile
    SKSpriteNode * projectile = [self childNodeWithName:@"desirednode"];
    //make projectile point to your desired node.

    // 3- Determine offset of location to projectile
    CGPoint offset = rwSub(location, projectile.position);

    // 4 - Bail out if you are shooting down or backwards. You can ignore this if required.
    if (offset.x <= 0) return;

    // 5 - OK to add now - we've double checked position
    [self addChild:projectile];

    // 6 - Get the direction of where to shoot
    CGPoint direction = rwNormalize(offset);

    // 7 - Make it shoot far enough to be guaranteed off screen
    float forceValue = 200; //Edit this value to get the desired force.
    CGPoint shootAmount = rwMult(direction, forceValue);

    //8 - Convert the point to a vector
    CGVector impulseVector = CGVectorMake(shootAmount.x, shootAmount.y);
    //This vector is the impulse you are looking for.

    //9 - Apply impulse to node.
    [projectile.physicsBody applyImpulse:impulseVector];

}

The projectile object in the code represents your node. Also, you will need to edit the forceValue to get the desired impulse.