CODEWITHSUNDEEP
sprite-kit
user3299383
user3299383

Reputation: 223

Using SpriteKit how can you move sprite nodes to a point with a random but consistent speed

I'm currently making my first sprite game and one of the things i have implemented into my game is objects coming in from the side, move all the way across the screen, and then be removed from the parent. Here's what that looks like.

MyScene.m 

-(void)createObstacle0 {
    CGPoint startPoint = CGPointMake(-20, 100);
    SKSpriteNode *obstacle = [SKSpriteNode spriteNodeWithImageNamed:@"obstacle"];
    obstacle.position = CGPointMake(startPoint.x, startPoint.y);
    obstacle.name = @"obstacle0";
    [self addChild:obstacle];

    float randomNum = arc4random_uniform(2) + 1.92;
    [self performSelector:@selector(createObstacle0) withObject:nil   afterDelay:randomNum];
}

excerpt from update method

[self enumerateChildNodesWithName:@"obstacle0" usingBlock:^(SKNode *node, BOOL *stop)     {
        if (node.position.x > 360) {
            [node removeFromParent];
        } else {
            node.position = CGPointMake(node.position.x + 5.2, node.position.y);
        }

    }];

At the moment, my objects only move across the screen at one speed. I tried using arc4random inside the currentTime method code, but because thats evaluated every frame, my object would not stay at one speed. It would speed up, slow down, and look very erratic. How can i change my code in CurrentTime to allow my objects crossing the screen to be set a random speed as soon as its made and to keep it until it is destroyed?

Second question:

int yMin = 90;
int yMax = 110;
CGPoint startPoint = CGPointMake(-20, yMin + arc4random_uniform(yMax - yMin));

Upvotes: 1

Views: 1406

Answers (1)

nacross
nacross

Reputation: 2043

I would suggest that instead of manually updating the child nodes position to move it from one side to another you create your obstacle and then call runAction: on it using an SKAction created with the moveTo:duration: method. You specify the final point you want your obstacle to end up at as well as how long you want this move to take. Pass in a random number with in the minimum and maximum time you want it to take to duration.

This should allow you to create consistent but randomised object movement.

int MAX_TIME = 20;
int MIN_TIME = 10;
[obstacle runAction:[SKAction moveTo:CGPointMake( 10, 100 ) duration:MIN_TIME + arc4random_uniform( MAX_TIME - MIN_TIME )]];

Upvotes: 1

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