Not able to apply impulse to SKSpriteNode physics body

问题

I am new to xcode's sprite kit and I'm an trying to apply an impulse to a SKSpriteNode's physics body. Here is how I create the scene:

self.backgroundColor = [SKColor colorWithRed:0 green:0 blue:0 alpha:1.0];
        self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
        self.physicsBody.friction = 0.0f;
        self.physicsWorld.gravity = CGVectorMake(0.0f, 0.0f);
        ballCategory = 1;
        wallCategory = 2;
        self.physicsBody.categoryBitMask = wallCategory;

Here is how I create the player AND give it its impulse:

player = [SKSpriteNode spriteNodeWithImageNamed:filePath];
    player.size = CGSizeMake(100, 100);
    player.position = CGPointMake(150, 250);
    player.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:player.frame];
    player.physicsBody.categoryBitMask = ballCategory;
    player.physicsBody.collisionBitMask = wallCategory;
    player.physicsBody.friction = 0.0f;
    player.physicsBody.restitution = 1.0f;
    player.physicsBody.linearDamping = 0.0f;
    player.physicsBody.allowsRotation = NO;
    [self addChild:player];
        CGVector impulse = CGVectorMake(100,100);
        [player.physicsBody applyImpulse:impulse];

Is there anything obvious that I am missing because I've been following the iOS Developer Library Sprite Kit Programming Guide perfectly? Thanks in advance for the help!

回答1:

You are creating the player's physicsBody as an edge body - these are always static (immovable by forces/impulses). You should change that line to:

player.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:player.frame.size];

This example makes it a dynamic volume based on a rectangle which will be affected by physics forces. You can read up on the types of physics bodies here.

来源：https://stackoverflow.com/questions/21163641/not-able-to-apply-impulse-to-skspritenode-physics-body

标签

sprite-kit

skphysicsbody