I want a ball-sprite jump off the ground each time to the same height. But with every jump the maximum height position of the ball increases.
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
SKNode *ground = [SKNode node];
ground.physicsBody = [SKPhysicsBody bodyWithEdgeFromPoint:CGPointZero toPoint:CGPointMake(CGRectGetMaxX(self.frame), 0)];
[self addChild:ground];
SKShapeNode *ball = [[SKShapeNode alloc] init];
CGMutablePathRef myPath = CGPathCreateMutable();
CGPathAddArc(myPath, NULL, 0, 0, 30, 0, M_PI*2, YES);
ball.path = myPath;
ball.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMaxY(self.frame)-100);
ball.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:ball.frame.size.width/2];
ball.physicsBody.linearDamping = 0.0;
ball.physicsBody.restitution = 1.0;
[self addChild:ball];
}
return self;
}
Any suggestions?
Look at setting both the restitution and friction on both bodies, not just the ball. If it's growing and not shrinking though, there is likely an error with the physics bodies. SKShapeNode is notoriously unreliable in my testing - I would look into using SKSpriteNode instead to maintain your sanity.
Related
SO following an IOS game tutorial, its IO7 as not many for 8 are out yet.
The following code is supposed to be a ball bouncing around but only bounces on the top and bottom of the screen, if it hits the side edges the ball goes of screen
#import "GameScene.h"
#implementation GameScene
-(void)didMoveToView:(SKView *)view {
/* Setup your scene here */
self.backgroundColor =[SKColor whiteColor];
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.physicsWorld.gravity = CGVectorMake(0, 0);
SKSpriteNode *ball = [SKSpriteNode spriteNodeWithImageNamed:#"ball"];
ball.position = CGPointMake(CGRectGetMidX(self.frame),CGRectGetMidY(self.frame));
ball.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:ball.frame.size.width/2];
//ball.physicsBody.friction = 0;
ball.physicsBody.linearDamping = 0;
ball.physicsBody.restitution = 1;
[self addChild:ball];
CGVector myVector = CGVectorMake(0, 5);
[ball.physicsBody applyImpulse:myVector];
}
-(void)update:(CFTimeInterval)currentTime {
/* Called before each frame is rendered */
}
#end
There has to be something simple here but i can't seem to find an answer on stack overflow
Use NSLog to check the size of your view: NSLog(#"%f,%f",self.size.width,self.size.height);
There is a problem with SpriteKit that causes the view dimensions to be off of what you expect. If this is what is happening in your case, then make sure to change the size of your view to the correct one:
-(void)didMoveToView:(SKView *)view {
/* Setup your scene here */
self.size = self.view.frame.size;
self.backgroundColor =[SKColor whiteColor];
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.physicsWorld.gravity = CGVectorMake(0, 0);
SKSpriteNode *ball = [SKSpriteNode spriteNodeWithImageNamed:#"ball"];
ball.position = CGPointMake(CGRectGetMidX(self.frame),CGRectGetMidY(self.frame));
ball.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:ball.frame.size.width/2];
//ball.physicsBody.friction = 0;
ball.physicsBody.linearDamping = 0;
ball.physicsBody.restitution = 1;
[self addChild:ball];
CGVector myVector = CGVectorMake(50, 20);
[ball.physicsBody applyImpulse:myVector];
}
-(void)update:(CFTimeInterval)currentTime {
/* Called before each frame is rendered */
}
In the following example, there are three things on the screen:
ball (a SKShapeNode)
spriteContainer (a SKSpriteNode that contains ball2, a SKShapeNode)
box (a SKSpriteNode)
Why does ball fall out of view? Does a SKShapeNode need to be inside a SKSpriteNode to have physics properly applied to it?
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
SKColor * warmRed = [SKColor colorWithRed:0.99 green:0.41 blue:0.25 alpha:1.0];
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.backgroundColor = warmRed;
//falls out of view
SKShapeNode * ball = [[SKShapeNode alloc] init];
CGMutablePathRef ballPath = CGPathCreateMutable();
CGPathAddArc(ballPath, NULL, size.width-40, self.size.height/2, 20, 0, M_PI*2, YES);
ball.path = ballPath;
ball.lineWidth = 2;
ball.fillColor = warmRed;
ball.strokeColor = [SKColor whiteColor];
ball.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:20];
[self addChild:ball];
//lands on bottom of screen
SKShapeNode * ball2 = [[SKShapeNode alloc] init];
CGMutablePathRef ball2Path = CGPathCreateMutable();
CGPathAddArc(ball2Path, NULL, 0, 0, 20, 0, M_PI*2, YES);
ball2.path = ball2Path;
ball2.lineWidth = 2;
ball2.fillColor = warmRed;
ball2.strokeColor = [SKColor whiteColor];
CGSize spriteContainerSize = CGSizeMake(40,40);
CGPoint spriteContainerPosition = CGPointMake(size.width/2, size.height/2);
SKSpriteNode * spriteContainer = [SKSpriteNode spriteNodeWithColor:[SKColor blackColor] size:spriteContainerSize];
spriteContainer.position = spriteContainerPosition;
spriteContainer.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:spriteContainerSize];
[spriteContainer addChild:ball2];
[self addChild:spriteContainer];
//lands on bottom of screen
CGSize boxSize = CGSizeMake(40,40);
CGPoint boxPosition = CGPointMake(boxSize.width, size.height/2);
SKSpriteNode * box = [SKSpriteNode spriteNodeWithColor:[SKColor blackColor] size:boxSize];
box.position = boxPosition;
box.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:boxSize];
[self addChild:box];
}
return self;
}
Screenshot:
https://dl.dropboxusercontent.com/u/164157126/example.jpg
Note that you don't set a position for the node which falls off the screen, but set a position for the other two nodes you create.
The default position of a node is 0,0. Your ball will appear at the bottom left of the scene, and since it is over the edge body you defined, will fall off immediately.
Set the ball's position appropriately so that it does not intersect the edge of the screen, and the ball will not fall off.
If I apply an impulse of 1 in the y direction, the ball bounces back and forth without losing any energy. However, if the initial impulse is 0.5 or below, the ball loses all energy instantly when it hits the wall. Why is this happening? I have a pretty good understanding of the properties of the SKPhysicsBody class. Try this code to see if you get the same behavior on your computer.
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
/* Setup your scene here */
self.physicsWorld.gravity = CGVectorMake(0.0f, 0.0f);
SKPhysicsBody* borderBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.physicsBody = borderBody;
self.physicsBody.friction = 0.0f;
self.backgroundColor = [SKColor colorWithRed:0.7 green:0.7 blue:0.7 alpha:1.0];
SKShapeNode *ball = [SKShapeNode node];
CGMutablePathRef pathToDraw = CGPathCreateMutable();
[ball setStrokeColor:[UIColor blackColor]];
CGPathMoveToPoint(pathToDraw, NULL, 0, 0);
CGPathAddEllipseInRect(pathToDraw, NULL, CGRectMake(-16, -16, 32, 32));
ball.path = pathToDraw;
ball.position = CGPointMake(size.width / 2, size.height / 2);
ball.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:ball.frame.size.width/2];
ball.physicsBody.friction = 0.0f;
ball.physicsBody.restitution = 1.0f;
ball.physicsBody.linearDamping = 0.0f;
ball.physicsBody.allowsRotation = NO;
[self addChild:ball];
[ball.physicsBody applyImpulse:CGVectorMake(0, 0.5)];
}
return self;
}
When the collision velocity is small enough (such as your CGVector of (0, 0.5)), Box2d underlying the Sprite Kit physics engine will compute the collision as inelastic (i.e. as if the restitution was 0, removing any bounciness), and the node will not bounce.
This is, per the Box2d documentation, to prevent jitter.
In the Box2d source code, you even have this line:
/// A velocity threshold for elastic collisions. Any collision with a relative linear
/// velocity below this threshold will be treated as inelastic.
#define b2_velocityThreshold
Your impulse should be above this threshold for the restitution to be respected.
I want to make a soccer ball by IOS SpriteKit
I was able to create a ball in the code such as the following.
However, it does not bounce at all.
To make rebound rate, How can I do this?
(UITouch *touch in touches) {
SKSpriteNode *sprite = [SKSpriteNode spriteNodeWithImageNamed:#"Ball"];
sprite.position = location;
const CGFloat radius = 20.0f;
SKPhysicsBody *pbody = [SKPhysicsBody bodyWithCircleOfRadius:radius];
sprite.physicsBody = pbody;
sprite.size = (CGSize){radius * 2, radius * 2};
sprite.physicsBody.linearDamping=0.12f;
[self addChild:sprite];
}
I have declared like this.
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
self.backgroundColor = [SKColor colorWithRed:0.15 green:0.15 blue:0.3 alpha:1.0];
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:(CGRect){CGPointZero, size}];
self.physicsWorld.gravity=CGVectorMake(0, -100);
}
return self;
}
This looks like a ball to me
- (void) soccerBallExample
{
// the world bounds
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:CGRectMake(0, 0, self.size.width, self.size.height)];
// the ball
SKShapeNode *ball;
ball = [[SKShapeNode alloc] init];
CGMutablePathRef myPath = CGPathCreateMutable();
CGPathAddArc(myPath, NULL, 0,0, 30, 0, M_PI*2, YES);
ball.path = myPath;
CGPathRelease(myPath);
ball.fillColor = [SKColor blueColor];
ball.position = CGPointMake(200, 200);
[self addChild:ball];
// set the physics
ball.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:30];
ball.physicsBody.restitution = 0.8;
}
In your example, you use a sprite so for radius use
// ball.size.width * 0.5;
I'm testing out pin joints with Sprite Kit, and I'm finding something unusual happening.
My desired setup is this: one wide, flat box, and two circles; the circles are connected via SKPhysicsPinJoints to the box, so they can act as wheels.
Here's my code. I've tried to make it as concise as possible:
- (SKNode*) createWheelWithRadius:(float)wheelRadius {
CGRect wheelRect = CGRectMake(-wheelRadius, -wheelRadius, wheelRadius*2, wheelRadius*2);
SKShapeNode* wheelNode = [[SKShapeNode alloc] init];
wheelNode.path = [UIBezierPath bezierPathWithOvalInRect:wheelRect].CGPath;
wheelNode.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:wheelRadius];
return wheelNode;
}
- (void) createCar {
// Create the car
SKSpriteNode* carNode = [SKSpriteNode spriteNodeWithColor:[SKColor yellowColor] size:CGSizeMake(150, 50)];
carNode.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:carNode.size];
carNode.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));
[self addChild:carNode];
// Create the left wheel
SKNode* leftWheelNode = [self createWheelWithRadius:30];
leftWheelNode.position = CGPointMake(carNode.position.x-80, carNode.position.y);
[self addChild:leftWheelNode];
// Create the right wheel
SKNode* rightWheelNode = [self createWheelWithRadius:30];
rightWheelNode.position = CGPointMake(carNode.position.x+80, carNode.position.y);
[self addChild:rightWheelNode];
// Attach the wheels to the body
CGPoint leftWheelPosition = leftWheelNode.position;
CGPoint rightWheelPosition = rightWheelNode.position;
SKPhysicsJointPin* leftPinJoint = [SKPhysicsJointPin jointWithBodyA:carNode.physicsBody bodyB:leftWheelNode.physicsBody anchor:leftWheelPosition];
SKPhysicsJointPin* rightPinJoint = [SKPhysicsJointPin jointWithBodyA:carNode.physicsBody bodyB:rightWheelNode.physicsBody anchor:rightWheelPosition];
[self.physicsWorld addJoint:leftPinJoint];
[self.physicsWorld addJoint:rightPinJoint];
}
What I'm expecting is that the pin joints are anchored at their centre points; however, when I test this, the anchors for the joints appear to be far off.
Am I missing something really obvious?
I also had this issue and the cause is setting the physics body before setting the sprites position.
carNode.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:carNode.size];
carNode.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));
Change the above to
carNode.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));
carNode.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:carNode.size];
It should work. Thanks Smick.
SpriteKit: How to create Basic Physics Joints
Try this code, I used yours and got weird issues, so started from scratch.
- (SKShapeNode*) makeWheel
{
SKShapeNode *wheel = [[SKShapeNode alloc] init];
CGMutablePathRef myPath = CGPathCreateMutable();
CGPathAddArc(myPath, NULL, 0,0, 16, 0, M_PI*2, YES);
wheel.path = myPath;
return wheel;
}
- (void) createCar
{
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:CGRectMake(0, 0, self.size.width, self.size.height)];
// 1. car body
SKSpriteNode *carBody = [SKSpriteNode spriteNodeWithColor:[UIColor whiteColor] size:CGSizeMake(120, 8)];
carBody.position = CGPointMake(200, 200);
carBody.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:carBody.size];
[self addChild:carBody];
// 2. wheels
SKShapeNode *leftWheel = [self makeWheel];
leftWheel.position = CGPointMake(carBody.position.x - carBody.size.width / 2, carBody.position.y);
leftWheel.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:16];
[self addChild:leftWheel];
SKShapeNode *rightWheel = [self makeWheel];
rightWheel.position = CGPointMake(carBody.position.x + carBody.size.width / 2, carBody.position.y);
rightWheel.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:16];
[self addChild:rightWheel];
// 3. Join wheels to car
[self.physicsWorld addJoint:[SKPhysicsJointPin jointWithBodyA:carBody.physicsBody bodyB:leftWheel.physicsBody anchor:leftWheel.position]];
[self.physicsWorld addJoint:[SKPhysicsJointPin jointWithBodyA:carBody.physicsBody bodyB:rightWheel.physicsBody anchor:rightWheel.position]];
// 4. drive car
[carBody.physicsBody applyForce:CGVectorMake(10, 0)];
}