图片不适合SKSpriteNode框架

Question

I'm trying to create a player node on my scene. But the image "player.png" doesn't fit the physics body. They are both separate.

PhysicsBody is in the ground and the image is floating on the air. What's wrong with my code? How do I make them both together?

#import "Player.h"

@implementation Player
- (instancetype)init {
    self = [super initWithImageNamed:@"player.png"];
    self.name = @"player";
    self.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:CGSizeMake(50, 50)];
    self.physicsBody.dynamic = YES;
    self.physicsBody.allowsRotation = NO;
    self.physicsBody.affectedByGravity = YES;

    self.zPosition = 100;
    self.anchorPoint = CGPointMake(0.5, 0);

    return self;
}

@end
// myScene.h
-(void)createSceneContents {
    self.currentBackground = [Background generateBackground];
    [self addChild: self.currentBackground];
    self.physicsWorld.gravity = CGVectorMake(0, _gravity);
    self.physicsWorld.contactDelegate = self;

    Player *player = [[Player alloc]init];
    player.position = CGPointMake([UIScreen mainScreen].applicationFrame.size.width/2, 50);
    [self addChild:player];
}

Answer 1

Anchor point is the center of your physics body also here. Your point 0.5, 0.0 means center x and zero y. So, the center of your physics body is at the bottom edge of your sprite node. Likely the bottom center of the image. But the physics body extends downward from there. This is because of the method you used to create the physics body.

Anchor points are confusing. They play dual roles sometimes. They include a lot of poorly documented implicit behaviors.

Unless you have logic relying on the anchor point, it's best to shy away from changing them. With a physics body, what matters is where the body is in the physics world. Keep your model of the sprite as simple as possible. Refine constantly towards the simplest model to get the job done. It will simplify your game logic.