I have one sprite and my code is:
sprite.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:sprite.size.width/2];
sprite.physicsBody.dynamic = YES;
sprite.physicsBody.affectedByGravity = YES;
sprite.physicsBody.mass = 550.0f;
sprite.physicsBody.categoryBitMask = 1;
sprite.physicsBody.collisionBitMask = 1;
sprite.physicsBody.contactTestBitMask = 1;
I can detect collision in:
- (void)didBeginContact:(SKPhysicsContact *)contact {
// destroy contact.bodyA , contact.bodyB
}
But how can I destroy/remove these bodies from physics world?
I'm not sure if I completely understand, but if you're looking for a way of removing your sprites upon collision, you have to access each physics body's node property, and call its removeFromParent function.
[contact.bodyA.node removeFromParent];
[contact.bodyB.node removeFromParent];
Of course, you'll want to add additional logic to determine whether the bit masks of the colliding sprites are the same as the ones you wish to destroy during collision.
Related
I am having trouble getting collision detection to work with my two objects. Here is my current code:
_firstPosition = CGPointMake(self.frame.size.width * 0.817f, self.frame.size.height * .40f);
_squirrelSprite = [SKSpriteNode spriteNodeWithImageNamed:#"squirrel"];
_squirrelSprite.position = _firstPosition;
_atFirstPosition = YES;
[self addChild:_squirrelSprite];
SKAction *wait = [SKAction waitForDuration:3.0];
SKAction *createSpriteBlock = [SKAction runBlock:^{
SKSpriteNode *lightnut = [SKSpriteNode spriteNodeWithImageNamed:#"lightnut.png"];
BOOL heads = arc4random_uniform(100) < 50;
lightnut.position = (heads)? CGPointMake(257,600) : CGPointMake(50,600);
[self addChild: lightnut];
SKAction *moveNodeUp = [SKAction moveByX:0.0 y:-700.0 duration:1.3];
[lightnut runAction: moveNodeUp];
}];
SKAction *waitThenRunBlock = [SKAction sequence:#[wait,createSpriteBlock]];
[self runAction:[SKAction repeatActionForever:waitThenRunBlock]];
I was following this answer at first: Sprite Kit Collision Detection but when I set the physics body to my squirrel and nut they would just fall. Is there any way to not mess with the physics (I'm happy with how everything currently works in the app) and just make it so that when one object touches the other the game will end? Is there a way to just set a radius around a sprite? Thank you for any help or information that can be provided.
Physics bodies are required for collision detection. If you don't also want gravity, either set the physics world's gravity to zero or turn off the affectedByGravity property on each physics body.
You can use the Pythagorean theorem to determine the distance between two sprite nodes. Here's an example of how to do that:
CGFloat dx = sprite1.position.x - sprite2.position.x;
CGFloat dy = sprite1.position.y - sprite2.position.y;
CGFloat distance = sqrt(dx*dx+dy*dy);
// Check if the two nodes are close
if (distance <= kMaxDistance) {
// Do something
}
I want to make two sprites disappear when they hit each other in sprite kit. The example in apple's documentation doesn't really help me that much so if you could explain it it would be good. :)
OK, so you need to do several things.
I'm going to assume that you have two sprites...
SKSpriteNode *sprite1;
SKSpriteNode *sprite2;
These are currently flying around your scene and may or may not come into contact with each other.
So, you need to set everything up to enable hit testing and call backs.
First, add physics bodies to the sprites...
sprite1.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:10];
sprite2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:CGSizeMake(10, 10)];
// this is a couple of examples, you'll have to set yours up to match the sprite size, shapes
Next you need to add categories to the sprites. This gives the physics engine some information about what type of body it is...
sprite1.physicsBody.categoryBitMask = 1 << 0;
sprite2.physicsBody.categoryBitMask = 1 << 1;
// again this is an example. You probably want to put these in an NS_OPTIONS typedef.
Then you need to tell the physics engine which contact you want to be told about. In the is case you want to be told when sprite1 (1 << 0) comes into contact with sprite2 (1 << 1).
So...
sprite1.physicsBody.contactTestBitMask = 1 << 1; // it will test for contact against sprite 2
sprite2.physicsBody.contactTestBitMask = 1 << 0; // test against sprite 1.
Now in you scene you need to adopt <SKPhysicsContactDelegate> and set the scene to be the physics delegate...
self.physicsWorld.contactDelegate = self;
And then create the method...
- (void)didBeginContact:(SKPhysicsContact *)contact
{
// these two physics bodies have come into contact!
SKSpriteNode *firstContactNode = contact.bodyA.node;
SKSpriteNode *secondContactNode = contact.bodyB.node;
// now remove them...
[firstContactNode removeFromParent];
[secondContactNode removeFromParent];
}
SKAction* _vanishAction =[SKAction fadeOutWithDuration: 1];
[sprite runAction:_vanishAction completion:^(void){
[sprite removeFromParent];
}];
I have a node which is placed under my screen and works as a platform. As soon as another node touches the node a boolean is set to NO.
When I define my node with the SKPhysicsBody properties for the collision the node ignores the affectedByGravity property.
My code:
+ (void)addNewNodeTo:(SKNode *)parentNode
{
//Correct image size
SKSpriteNode *desertBottom = [SKSpriteNode node];
desertBottom = [[SKSpriteNode alloc] initWithImageNamed:#"Giraffe.png"];
desertBottom.position = CGPointMake(0, -200);
desertBottom.zPosition = 2;
desertBottom.physicsBody.collisionBitMask = lionType;
desertBottom.physicsBody.categoryBitMask = terrainType;
desertBottom.physicsBody.contactTestBitMask = lionType;
desertBottom.zPosition = 2;
desertBottom.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:CGSizeMake(desertBottom.size.width, desertBottom.size.height)];
desertBottom.physicsBody.dynamic = YES;
desertBottom.physicsBody.affectedByGravity = NO;
[parentNode addChild:desertBottom];
}
My collision methods:
- (void)didBeginContact:(SKPhysicsContact *)contact
{
uint32_t collision = (contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask);
if (collision == (lionType | terrainType)) {
self.lionNode.lionIsJumping = NO;
NSLog(#"%i", self.lionNode.lionIsJumping);
}
}
- (void)didEndContact:(SKPhysicsContact *)contact
{
uint32_t collision = (contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask);
if (collision == (lionType | terrainType)) {
self.lionNode.lionIsJumping = YES;
NSLog(#"%i", self.lionNode.lionIsJumping);
}
}
A physics body has a velocity. Gravity changes velocity over time. If the body is already traveling at a certain velocity due to gravity, and you disable gravity, it will continue to move according to its current velocity but no longer gain additional speed from gravity.
My guess is that you expect the body to stop when disabling gravity. If that's what you want you can do this manually by setting the y component of velocity to zero:
SKPhysicsBody* body = desertBottom.physicsBody;
body.velocity = CGVectorMake(body.velocity.x, 0.0);
If the platform should not move after a collision you have to set the dynamic property to false.
Maybe you have an issue with you bit masks?
Have you tried to log outside your if statement of the didBeginContact method?
I have created a new class with subclass of SKSpriteNode for the bottom and added it to my GameScene.
I'm trying to make a simple game with sprite kit.
The basic idea is that there is one player who can jump to avoid blocks.
But i have a problem I don't know how to make it that when the player hits the block the player disappears and the blood animation starts.
First of all i don't understand what this code does that I found on apples website.
static const uint32_t blockCategory = 0x1 <<0;
static const uint32_t playerCategory = 0x1 <<1;
Than i am calling the didBeginContact function and put a NSLOG("did call function") in it.
But i never receive the output in my debugger.
Here is my _player and _block code:
-(SKSpriteNode *)character {
_player = [SKSpriteNode spriteNodeWithImageNamed:#"soldier_run1"];
_player.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:_player.size.width /2 -5];
_player.physicsBody.dynamic = YES;
_player.physicsBody.usesPreciseCollisionDetection = YES;
_player.physicsBody.friction = 0;
_player.physicsBody.categoryBitMask = playerCategory;
_player.physicsBody.collisionBitMask = blokCategory;
_player.name = #"player";
SKAction *animAction = [SKAction animateWithTextures:playerTextures timePerFrame:0.1 resize:YES restore:YES];
My _player code:
[_player runAction:[SKAction repeatActionForever:animAction]];
return _player;
}
-(SKSpriteNode *)block {
_blok = [[SKSpriteNode alloc] initWithColor:[SKColor blackColor] size:CGSizeMake(15, 40)];
//physics
_blok.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:_blok.size];
_blok.physicsBody.dynamic = NO;
_blok.name = #"block";
_blok.physicsBody.categoryBitMask = blokCategory;
_blok.physicsBody.collisionBitMask = playerCategory;
SKAction *moveBlock = [SKAction sequence:#[
[SKAction moveToX:-20 duration:2] ]];
[_blok runAction:moveBlock ];
return _blok;
}
Also i don't really understand what the categoryBitMask and collisionBitMask do.
After i have that working i would like to make the character disappear from the screen and the blood animation to start, but I have no idea how to let that happen. I think you have to do something like:
if(_player && _block didcollide) {
}
But I don't know how to do it exactly.
The categoryBitMask sets the category that the sprite belongs to, whereas the collisionBitMask sets the category with which the sprite can collide with and not pass-through them.
For collision detection, you need to set the contactTestBitMask. Here, you set the categories of sprites with which you want the contact delegates to be called upon contact.
What you have already done is correct. Here are a few additions you need to do:
_player.physicsBody.contactTestBitMask = blockCategory;
_blok.physicsBody.contactTestBitMask = playerCategory;
Afterwards, implement the contact delegate as follows:
-(void)didBeginContact:(SKPhysicsContact *)contact`
{
NSLog(#"contact detected");
SKPhysicsBody *firstBody;
SKPhysicsBody *secondBody;
if (contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask)
{
firstBody = contact.bodyA;
secondBody = contact.bodyB;
}
else
{
firstBody = contact.bodyB;
secondBody = contact.bodyA;
}
//Your first body is the block, secondbody is the player.
//Implement relevant code here.
}
For a good explanation on implementing collision detection, look at this tutorial.
Handling collisions is a bit messy. :) There are a number of approaches, but one place you should start with is this fairly simple example from Apple. The readme provides a good intro, and then you can start poking around with the code.
Another approach (which Apple mentions in their guide) is to use Double Dispatching (see wikipedia for a long desc). I wouldn't start by trying to grok that approach right off however. It is a somewhat advanced approach given it depends on dynamic selectors and similar techniques to enable the magic to take place. However, even with that caveat, you can find a simple example someone put together on how to do it, along with a lot of supporting description here.
I'm using collision detection in Sprite Kit. It is working and preventing my sprites from crossing paths. However, I'm not getting notifications in didBeginContact: and I don't seem to have any control over how the physics engine responds when a collision occurs.
I have various cars (SKSpriteNodes) moving around following paths using the SKAction followPath:asOffset:orientToPath:duration:
Previously, if two cars crossed paths they would both just continue as normal with one driving over the other. To implement collision detection I have made the following changes...
Added this to my #interface:
<SKPhysicsContactDelegate>
Added this to my #implementation:
static const uint32_t carCategory = 0x1 << 0;
Added this in my init method:
self.physicsWorld.contactDelegate = self;
self.physicsWorld.gravity = CGVectorMake(0.0, 0.0);
I create my blue car:
- (void)addBlueCar
{
_blueCar = [SKSpriteNode spriteNodeWithImageNamed:#"Blue Car.png"];
_blueCar.position = CGPointMake(818.0, -50.0);
_blueCar.name = #"car";
[self addChild:_blueCar];
CGSize contactSize = CGSizeMake(_blueCar.size.width - 5.0, _blueCar.size.height - 5.0);
_blueCar.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:contactSize];
_blueCar.physicsBody.categoryBitMask = carCategory;
_blueCar.physicsBody.collisionBitMask = carCategory;
_blueCar.physicsBody.contactTestBitMask = carCategory;
}
And I also create a red car:
- (void)addRedCar
{
_redCar = [SKSpriteNode spriteNodeWithImageNamed:#"Red Car.png"];
_redCar = CGPointMake(818.0, -50.0);
_redCar = #"car";
[self addChild: _redCar];
CGSize contactSize = CGSizeMake(_blueCar.size.width - 5.0, _blueCar.size.height - 5.0);
_redCar.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:contactSize];
_redCar.physicsBody.categoryBitMask = carCategory;
_redCar.physicsBody.collisionBitMask = carCategory;
_redCar.physicsBody.contactTestBitMask = carCategory;
}
There are other cars as well, but I'm just using these two until I figure out what the problem is. I want to be notified of any collision between any two cars. That's why I'm just using a single category, carCategory.
The first problem is that I get no notifications. I have this yet it never logs anything to the console:
- (void)didBeginContact:(SKPhysicsContact *)contact
{
NSLog(#"Contact");
}
The second problem is that when two cars cross paths they start nudging each other off course. This is ok, but I don't seem to able to manage any aspects of how the collision is handled. The bizarre thing is that nothing changes when I do this to both of my car creation methods:
- (void)addBlueCar
{
_blueCar = [SKSpriteNode spriteNodeWithImageNamed:#"Blue Car.png"];
_blueCar.position = CGPointMake(818.0, -50.0);
_blueCar.name = #"car";
[self addChild:_blueCar];
CGSize contactSize = CGSizeMake(_blueCar.size.width - 5.0, _blueCar.size.height - 5.0);
_blueCar.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:contactSize];
// _blueCar.physicsBody.categoryBitMask = carCategory;
// _blueCar.physicsBody.collisionBitMask = carCategory;
// _blueCar.physicsBody.contactTestBitMask = carCategory;
}
Collision detection still works the same with those three lines commented out for both cars. This just doesn't seem right to me. Collision detection only ceases when I also comment out this line:
_blueCar.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:contactSize];
So my main question is: why is the contactTest not reporting anything? My second question is: why is collision detection happening when I don't assign a categoryBitMask, collisionBitMask or contactTestBitMask to any car?
collisionBitMask's default value is 0xFFFFFFFF (all bits set). Therefore the node will collide with each physicBody on the scene.
Just a small observation, perhaps you should setup your nodes and set the contact delegate in the scene's didMoveToView method.
If that doesn't solve it, any chance you can post some working code to github for debugging?
Something that helped me with this: Collisions and contacts are different things.
Collision is handled by the physics engine and setting collisionBitMask will determine which bodies collide and interact with each other in the physics world. By default, all your bodies will collide with each other, which kinda makes sense.
Contacts are events- when bodies make contact, will they create a notification that you can use in the delegate method to do more interesting things. If you have a ball you want to hit with a paddle, you want them to collide at a minimum. But if you have a ball moving through a cloud, you probably don't want them to collide in the physics world, but you might want to register the contact.