swift - How to apply impulse to the node on touch angle -

i want node move in right direction impulse set strength.

let node: skspritenode!;  node = skspritenode(color: uicolor.greencolor(), size: cgsizemake(50, 50)); node.physicsbody = skphysicsbody(rectangleofsize: node.size); node.physicsbody?.affectedbygravity = false; node.physicsbody?.allowsrotation = false;  override func touchesbegan(touches: set<nsobject>, withevent event: uievent) {      node.physicsbody?.velocity = cgvectormake(0, 0);         // ver 1          node.physicsbody?.applyimpulse(cgvectormake((0.4) * (location.x - node.position.x), (0.4) * (location.y - node.position.y)), atpoint: cgpointmake(position.x,position.y));      // ver 2     let offset:cgpoint = self.vecsub(location, b: ghost.position);     let direction: cgpoint = self.vecnormalize(offset);     var len: cgpoint = self.vecmult(direction, b: 40);     let impulsevector:cgvector = cgvectormake(len.x, len.y);     ghost.physicsbody?.applyimpulse(impulsevector);  }  func vecadd(a: cgpoint, b:cgpoint) -> cgpoint {     return cgpointmake(a.x + b.x, a.y + b.y); }  func vecsub(a: cgpoint, b:cgpoint) -> cgpoint {     return cgpointmake(a.x - b.x, a.y - b.y); }  func vecmult(a: cgpoint, b:cgfloat) -> cgpoint {     return cgpointmake(a.x * b, a.y * b); }  func veclenght(a:cgpoint)->cgfloat{     return cgfloat( sqrtf( cfloat(a.x) * cfloat(a.x) + cfloat(a.y) * cfloat(a.y))); }  func vecnormalize(a:cgpoint)->cgpoint{     let len : cgfloat = self.veclenght(a);     return cgpointmake(a.x / len, a.y / len); } 

• version 1 horrible

• version 2 okay, expensive

• version 3: not expensive , apply impulse 15-100 strength, because if touch @ edges of screen node should move 15-100 of current possition without reaching touch position

both methods you've detailed above work i'm not sure you're problem is. also, i'm not sure method 2 it's expensive, having frame rate drops using it?

but i've got way you're after, it's second version cleaned up. firstly wanted point out couple things current code:

1. don't need ; end of each line.

2. instead of using vecadd, vecsub etc overload +, -, * , / operators make code cleaner , clearer. way, operators global use them anywhere else need manipulate vectors.

anyway, here's attempt @ it:

firstly, extend cgvector add functionality need. things length, defining functions, properties of cgvector:

extension cgvector {     init(p1: cgpoint, p2: cgpoint) {         self.dx = p1.x - p2.x         self.dy = p1.y - p2.y     }      var length: cgfloat {         { return hypot(dx, dy) }          set {             normalise()             dx *= newvalue             dy *= newvalue         }     }      mutating func normalise() {         dx /= length         dy /= length     } } 

secondly, using new methods:

var vec = cgvector(p1: location, p2: ghost.position) vec.length = 40 ghost.physicsbody!.applyimpulse(vec) 

alternatively, if wanted size of impulse relate how far away ghost user pressed, use following:

vec.length *= 0.1  

hope helps!