CODEWITHSUNDEEP
objective-csprite-kitpolygonskphysicsbody
PoKoBros
PoKoBros

Reputation: 721

Creating a SKPhysicsBody on a triangular sprite

I have a sprite that looks like this.

enter image description here

How would I create an SKPhysicsBody for this sprite? I want it so that the SKPhysicsBody either is a triangle or it is just an edge on the long side of the sprite. Here is what I have so far. The sprite, called rightEnemy, has an anchor point of 

CGPointMake(0.5, 0.5);
rightEnemy.physicsBody = [SKPhysicsBody bodyWithEdgeFromPoint:CGPointMake(rightEnemy.position.x + width, rightEnemy.position.y) toPoint:CGPointMake(rightEnemy.position.x, rightEnemy.position.y + height)];

This creates a physics body but for some reason it is not attached to the sprite.

The sprite that the physics body is attached to is moving constantly via the update method. The y value is always changing.

Upvotes: 3

Views: 473

Answers (3)

Mike Zriel
Mike Zriel

Reputation: 1865

Here is the Swift version of the answer.

    var trianglePath:CGMutablePathRef = CGPathCreateMutable()
    CGPathMoveToPoint(trianglePath, nil, -self.size.width/2, self.size.height/2)
    CGPathAddLineToPoint(trianglePath, nil, self.size.width/2, -self.size.height/2)
    CGPathAddLineToPoint(trianglePath, nil, -self.size.width/2, -self.size.height/2)
    CGPathAddLineToPoint(trianglePath, nil, -self.size.width/2, self.size.height/2)

    self.physicsBody? = SKPhysicsBody( polygonFromPath: trianglePath)

Upvotes: 3

sangony
sangony

Reputation: 11696

You can create a triangle shaped physics body like this:

CGMutablePathRef trianglePath = CGPathCreateMutable();
CGPathMoveToPoint(trianglePath, nil, -myNode.size.width/2, myNode.size.height/2);
CGPathAddLineToPoint(trianglePath, nil, myNode.size.width/2, -myNode.size.height/2);
CGPathAddLineToPoint(trianglePath, nil, -myNode.size.width/2, -myNode.size.height/2);
CGPathAddLineToPoint(trianglePath, nil, -myNode.size.width/2, myNode.size.height/2);
myNode.physicsBody = [SKPhysicsBody bodyWithPolygonFromPath:trianglePath];

CGPathRelease(trianglePath);

The above creates a 45 degree right facing triangle.

Upvotes: 1

Skyler Lauren
Skyler Lauren

Reputation: 3812

You may want to try to create the physical body from the texture.

rightEnemy.physicsBody = [SKPhysicsBody bodyWithTexture:rightEnemy.texture size:rightEnemy.size];

You can also do this to validate if the physics is set correctly.

self.scene.view.showsPhysics = YES;

Edit

For iOS 7

Untested but I would imagine the bodyWithEdgeFromPoint: needs to be in the sprites coordinate system. You could try this which "should" draw a line from the bottom left to the top right corners of your sprite.

rightEnemy.physicsBody = [SKPhysicsBody bodyWithEdgeFromPoint:CGPointMake(-rightEnemy.size.width/2, -rightEnemy.size.height/2) toPoint:CGPointMake(rightEnemy.size.width/2, rightEnemy.size.height/3)];

Hopefully that helps.

Upvotes: 1

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