I am working on an iOS game using Sprite Kit.
I recently added an SKSpriteNode into my scene and did NOT create a physics body for it. However, when I build and run, when the player's character(which does have a physics body) moves into the SKSpriteNode, it spins and moves away, like it has a physics body -but I didn't create one for the SKSpriteNode.
Even if I type
sprite.physicsBody = nil;
it still behaves like it's part of the simulation.
I wondered if a physics body is created automatically when you make an SKSpriteNode, but I looked at the documentation and searched it on Google and couldn't find anything to suggest that is the case.
Any help or suggestions would be much appreciated.
This is the code I used to create the sprite (the one that should not be affected by the simulation)
-(void)addSprite
{
SKSpriteNode *sprite = [SKSpriteNode spriteNodeWithImageNamed:#"image"];
sprite.position = CGPointMake(40, 30);
sprite.zPosition = 30;
sprite.name = #"spriteName";
[self addChild:sprite];
}
In another part of the project I have
[self addSprite];
to call the method.
Yes every SKSpriteNode comes with a physics body. Its best to change the physics body's properties instead of getting rid of it altogether. If you want your sprite to be on screen and not interact with any other sprite nodes, do the following:
sprite.physicsBody.dynamic = NO;
sprite.physicsBody.collisionBitMask = 0x0;
sprite.physicsBody.contactTestBitMask = 0x0;
Related
I have a player character and a ground tile. On both physics bodies, I have restitution set to 0.
To jump, I directly set the velocity.dy of the player. When the player comes back to the ground due to gravity, for the most part it works, or seems to.
Problems occur when I repeatedly jump. If I jump right as the player lands, there's some bounce and the height the player reaches on the next bounce doesn't always match the initial bounce.
I've tried various ways to force the velocity.dy to 0 when the user lands, but nothing fixes the weird jumping issue. How can I properly and smoothly have a consistent physics jump?
Honestly, I am not sure what you are trying to accomplish. Normally we shouldn't mess with velocities of objects. In a typical Spritekit game, we must treat it like a "real world" situation and generally apply force or impulse on the object.
I suspect you are trying to make a Mario-like game. All you have to do is apply a big enough gravity to the physicsworld and apply impulse on the sprite to jump (on touchesBegan delegate).
Just now I went ahead and made a simple mario jump scenario in Spritekit. And this is what I ended up with by setting gravity -30 for the y-component and impulse y=100 on the mario sprite. (Frame rate is bad. Looks better on simulator/device)
PhysicsWorld setup:
[self.physicsWorld setGravity:CGVectorMake(0, -30)];
self.physicsWorld.contactDelegate = self;
Mario and platform sprite setup code:
SKSpriteNode *platform = [SKSpriteNode spriteNodeWithImageNamed:#"platform"];
platform.position = CGPointMake(view.frame.size.width/2.0,0);
platform.name = #"platform";
platform.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:platform.frame.size];
platform.physicsBody.categoryBitMask = platformCategory;
platform.physicsBody.dynamic = NO;
platform.physicsBody.usesPreciseCollisionDetection = YES;
platform.physicsBody.affectedByGravity = NO;
[self addChild:platform];
SKSpriteNode *mario = [SKSpriteNode spriteNodeWithImageNamed:#"mario"];
mario.position = CGPointMake(view.frame.size.width/2.0, 400);
mario.name = #"mario";
mario.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:mario.frame.size];
mario.physicsBody.categoryBitMask = marioCategory;
mario.physicsBody.dynamic = YES;
mario.physicsBody.usesPreciseCollisionDetection = YES;
mario.physicsBody.contactTestBitMask = platformCategory;
mario.physicsBody.affectedByGravity = YES;
[self addChild:mario];
touchesBegan:
SKSpriteNode *mario = (SKSpriteNode*)[self childNodeWithName:#"mario"];
[mario.physicsBody applyImpulse:CGVectorMake(0, 100)];
I'm very new to cocos2d development.
What I am trying to implement is some sprite nodes with physics bodies. As far as I understand, you're supposed to add them to the scene like this ("physics" here is the name of CCPhysicsNode declared earlier):
[physics addChild:node];
instead of
[self addChild:node];
The second one is pretty self-explanatory, I never had any trouble with it. But with the first the position of collision shapes does not match the position of the actual sprite (as seen in debug drawing, and by offset I mean greatly offset, like 2x the actual position). This is how I declare and add the node:
CCSprite *sprite = [CCSprite spriteWithImageNamed:#"sprite.png"];
sprite.position = position;
sprite.physicsBody = [CCPhysicsBody bodyWithRect:[sprite boundingBox] cornerRadius:0];
sprite.physicsBody.collisionType = #"SomeCollisionType";
sprite.name = #"Name";
[physics addChild:sprite];
What am I doing wrong? Please explain me how to make the positions match. TIA.
I am creating a game where I do not want the player to be able to move out of the screen. The node follows the players moving touch. The code I have "under construction" so the player can't move out on the top or right side, but I do not want the player to be able to move out on any of the sides.
- (void)movementPlayer {
SKAction * actionMoveX = [SKAction moveToX:MIN(location2.x - playerPositionX, self.size.width - (_player.size.width/2)) duration:0];
SKAction * actionMoveY = [SKAction moveToY:MIN(location2.y - playerPositionY, self.size.height - (_player.size.height/2)) duration:0];
[_player runAction:[SKAction sequence:#[actionMoveX, actionMoveY]]];
}
You should create a physics world and add a border rectangle around the screen. This border must have a physics body that is set to collide with the physics body collision category given to your player node. If the player node starts inside the border, the player cannot leave the screen and no additional coding is required (besides properly setting up collision categories for each physics body)
RayWenderlich.com has easy to understand game tutorials that show how to handle collisions following the sprite kit manual.
In your SKScene:
self.physicsBody=[SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.physicsWorld.gravity=CGVectorMake=(0,0);
_player.physicsBody=[SKPhysicsBody bodyWithRectangleOfSize:CGSizeMake(10,10)];//example; use bodyWithPolygonFromPath:yourCGPath if player has more complex form, or bodyWithCircleOfRadius:radius if its shape is circle
_player.physicsBody.velocity=CGVectorMake(10,10); //or more then 10,10
Good luck!
just add the bottom code to your method that is called it should stop all physical bodies from leaving the screen!! veryuseful!
SKPhysicsBody* gameborderBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
// 2 Set physicsBody of scene to borderBody
self.physicsBody = gameborderBody;
// 3 Set the friction of that physicsBody to 0
self.physicsBody.friction = 1.0f;
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'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.