I am trying to create a complex SKPhysicsBody that does not bounce on the top, but does allow bouncing on the sides and bottom. Currently I am creating two nodes. One that has the image of the Sprite and a no restitution PhysicsBody on the top.
My second node matches the first node, but is clear with the same size as the first node It just has a PhysicsBody on the front and bottom and has a restitution. to allow my main character to bounce off the bottom and front.
Here is the code for my current setup:
//This is the top part.
- (void)nodePhysicsBodySetup:(SKSpriteNode *)node
{
CGPoint topStart = CGPointMake(0, node.size.height);
CGPoint topEnd = CGPointMake(node.size.width, node.size.height);
SKPhysicsBody *topEdge = [SKPhysicsBody bodyWithEdgeFromPoint:topStart toPoint:topEnd];
node.physicsBody = topEdge;
//[SKPhysicsBody bodyWithBodies:#[topEdge, frontEdge, bottomEdge]]
//node.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:node.frame.size];
node.physicsBody.dynamic = NO;
node.physicsBody.restitution = 0.0;
node.physicsBody.affectedByGravity = NO;
node.physicsBody.categoryBitMask = groundCategory;
node.physicsBody.collisionBitMask = mainHeroCategory;
node.physicsBody.contactTestBitMask = mainHeroCategory;
}
//This is the bottom physicsbody that matches up with the image of the main node.
- (void)bottomNodePhysicsBodySetup:(SKSpriteNode *)node
{
CGPoint topStart = CGPointMake(0, node.size.height);
CGPoint frontEnd = CGPointMake(0,0);
CGPoint bottomEnd = CGPointMake(node.size.width,0);
SKPhysicsBody *frontEdge = [SKPhysicsBody bodyWithEdgeFromPoint:topStart toPoint:frontEnd];
SKPhysicsBody *bottomEdge = [SKPhysicsBody bodyWithEdgeFromPoint:frontEnd toPoint:bottomEnd];
bottomNode.physicsBody = [SKPhysicsBody bodyWithBodies:#[frontEdge, bottomEdge]];
bottomNode.physicsBody.dynamic = NO;
bottomNode.physicsBody.affectedByGravity = NO;
bottomNode.physicsBody.restitution = 0.5;
bottomNode.physicsBody.categoryBitMask = otherCategory;
bottomNode.physicsBody.collisionBitMask = mainHeroCategory;
bottomNode.physicsBody.contactTestBitMask = mainHeroCategory;
}
Picture as screenshots are under NDA:
Currently, the Green PhysicsBody is attached to the node, and the red PhysicsBody is attached to a transparent second node with the same position as the first node.
This does not really work. My main character (mainHeroCategory) gets stuck sometimes on the node corner where the PhysicsBody with restitution and the one without meet. What is a better way to do this?
I would try to do this using only one physics body and look at the contact delegate methods to determine where the contact occurred and what the normal vector is (that information is in the SKPhysicsContact object passed in the delegate method).
Once I got that information I would apply an impulse to the mainHeroCategory object, or not, depending on where the contact occurred.
I suggest you join the physics bodies with an SKPhysicsJointFixed or by constraining the bodies with an SKConstraint or two. SpriteKit only uses the shape when merging two or more bodies with bodyWithBodies. From the docs...
The properties on the children, such as mass or friction, are ignored.
Only the shapes of the child bodies are used.
The restitution property is ignored.
Related
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.
Two likely related things here:
1) I can draw a box and add to child from my SKScene impelmentation file with self, self.scene, and myWorld, but not with an SKSprite node's scene property.
SKSpriteNode *bla = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(100, 100)];
[self.scene addChild:bla]; // If I use bla.scene, it doesn't work. self, self.scene, myworld all do work though.
bla.position = CGPointMake(0, 0);
bla.zPosition = 999;
2) I've seen the related questions here and here, but I'm trying to add a joint during gameplay (grabbing a rope). This method gets called after doing some sorting in `didBeginContact:
-(void)monkey:(SKPhysicsBody *)monkeyPhysicsBody didCollideWithRope:(SKPhysicsBody *)ropePhysicsBody atPoint:(CGPoint)contactPoint
{
if (monkeyPhysicsBody.joints.count == 0) {
// Create a new joint between the player and the rope segment
CGPoint convertedRopePosition = [self.scene convertPoint:ropePhysicsBody.node.position fromNode:ropePhysicsBody.node.parent];
SKPhysicsJointPin *jointPin = [SKPhysicsJointPin jointWithBodyA:playerPhysicsBody bodyB:ropePhysicsBody anchor:convertedRopePosition];
jointPin.upperAngleLimit = M_PI/4;
jointPin.shouldEnableLimits = YES;
[self.scene.physicsWorld addJoint:jointPin];
}
}
I've got showPhyiscs enabled on the scene, so I can see that the joint is ending up in a totally wacky place. Unfortunately, I don't know how to apply the linked solutions since I'm not adding the SKSpriteNodes in this method, they already exist, so I can't just flip the order of position and physicsBody.
I've tried every permutation I could for both of the convertPoint methods. Nothing worked. My best guess is that physicsWorld is using some wacky coordinate system.
Method members of SKPhysicsWorld that relate to position (CGPoint) or frame (CGRect) are to be in scene coordinates. Scene coordinates reference the point {0,0} as the bottom left corner and is consistent throughout SpriteKit.
The scene property of your object named bla will be nil when bla is first created and is set by the scene when added to it.
[bla.scene addChild:bla]; // this won't do anything as scene will be nil when first created
It looks as though convertedRopePosition is being assigned an incorrect value because the second member you're passing into, - (CGPoint)convertPoint:(CGPoint)point fromNode:(SKNode *)node , is the scene when it should be another node in the same node tree as this node. where this node is the caller (in this case the SKScene subclass).
Try replacing the line-
CGPoint convertedRopePosition = [self.scene convertPoint:ropePhysicsBody.node.position fromNode:ropePhysicsBody.node.parent];
with-
CGPoint convertedRopePosition = [self convertPoint:ropePhysicsBody.node.position fromNode:ropePhysicsBody.node];
I came up with a janky work around for this problem. It turns out that the coordinate system offset for physicsWorld was likely due to an anchor difference. Changing the anchors of every related thing made no difference, and you can't change the anchor of the physicsWorld directly, so I ended up adding half of the scene width and half of the scene height to the anchor position of my joint. That got it to show in the right place and behave normally.
This problem persisted once side scrolling was factored in. I've posted other questions here with this same problem but I'll include th
I added the following convenience method to my GameScene.m. It essentially takes the place of the seemingly useless convertTo built in method.
-(CGPoint)convertSceneToFrameCoordinates:(CGPoint)scenePoint
{
CGFloat xDiff = myWorld.position.x - self.position.x;
CGFloat yDiff = myWorld.position.y - self.position.y;
return CGPointMake(scenePoint.x + self.frame.size.width/2 + xDiff, scenePoint.y + self.frame.size.height/2 + yDiff);
}
I use this method to add joints. It handles all of the coordinate system transformations that need to be dealt with that lead to the issue raised in this question. For example, the way I add joints
CGPoint convertedRopePosition = [self convertSceneToFrameCoordinates:ropePhysicsBody.node.position];
SKPhysicsJointPin *jointPin = [SKPhysicsJointPin jointWithBodyA:monkeyPhysicsBody bodyB:ropePhysicsBody anchor:convertedRopePosition];
jointPin.upperAngleLimit = M_PI/4;
jointPin.shouldEnableLimits = YES;
[self.scene.physicsWorld addJoint:jointPin];
It's possible for one node to have two physics body paths? I want to create a node that has two (circle) physics bodies on the sides of the node.
If it's not possible, is there are any workaround to achieve that? thank you
You want to use [SKPhysicsBody bodyWithBodies:...]. From the docs :
The shapes of the physics bodies passed into this method are used to
create a new physics body whose covered area is the union of the areas
of its children. These areas do not need to be contiguous. If there is
space between two parts, other bodies may be able to pass between
these parts. However, the physics body is treated as a single
connected body, meaning that a force or impulse applied to the body
affects all of the pieces as if they were held together with an
indestructible frame.
It would look something like this :
SKPhysicsBody *leftCircle = [SKPhysicsBody bodyWithCircleOfRadius:leftCircleRadius center:leftCircleCenter];
SKPhysicsBody *rightCircle = [SKPhysicsBody bodyWithCircleOfRadius:rightCircleRadius center:rightCircleCenter];
node.physicsBody = [SKPhysicsBody bodyWithBodies:#[leftCircle, rightCircle]];
Here's an example of how to connect to sprite nodes using SKPhysicsJointFixed. First, create two sprites:
SKSpriteNode *sprite1 = [SKSpriteNode spriteNodeWithColor:[SKColor blueColor] size:CGSizeMake(64, 64)];
// position must be set before creating physics body to avoid bug in iOS 7.0.x
sprite1.position = CGPointMake(CGRectGetMidX(self.frame),
CGRectGetMidY(self.frame));
sprite1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:sprite1.size];
sprite1.physicsBody.restitution = 1.0;
[self addChild:sprite1];
SKSpriteNode *sprite2 = [SKSpriteNode spriteNodeWithColor:[SKColor blueColor] size:CGSizeMake(64, 64)];
sprite2.position = CGPointMake(CGRectGetMidX(self.frame)-sprite2.size.width*2,
CGRectGetMidY(self.frame));
sprite2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:sprite2.size];
sprite2.physicsBody.restitution = 1.0;
[self addChild:sprite2];
then connect the nodes by calling this method:
[self connectNode1:sprite1 toNode2:sprite2];
This method joins two nodes at their midpoint. Note that both physic bodies must be in the scene prior to calling this method.
- (void) connectNode1:(SKSpriteNode *)node1 toNode2:(SKSpriteNode *)node2
{
CGPoint midPoint = CGPointMake((node1.position.x + node2.position.x)/2,
(node1.position.y + node2.position.y)/2);
SKPhysicsJointFixed *joint = [SKPhysicsJointFixed jointWithBodyA:node1.physicsBody
bodyB:node2.physicsBody
anchor:midPoint];
[self.physicsWorld addJoint:joint];
}
Here is an easy way to achieve the behavior you are looking for:
How to detect contact on different areas of a physicsbody
//Create SpriteNode1 & physicsBody
//Create SpriteNode2 & physicsBody
[SpriteNode1 addChild: SpriteNode2]
You can position SpriteNode2 relative to SpriteNode1. Any movement, etc. performed on SpriteNode1 will also move SpriteNode2.
Set: SpriteNode2.PhysicsBody.Dynamic=NO;
You could also create a SpriteNode that acts as the main object and add both SN1 and SN2 as children if you find that easier.
I have two spriteNodes that intersect but at different positions. both sprites are rectangular. I am getting some strange behavior where it only detects an intersection between the nodes if they intersect on the left half of one of the nodes (this node is always the same one and is always a stationary node). So what could cause such a behavior?
I do have some code I can show but it seems pretty straight forward so if anyone thinks it might help just let me know?
Update: it works with a different sprite here is the code for each of them:
if (!weldRUHit && [weldRU intersectsNode:[barriers objectAtIndex:i]]) {
SKSpriteNode *nodeA = (SKSpriteNode*)[barriers objectAtIndex:i];
SKPhysicsBody *firstBody = nodeA.physicsBody;
SKSpriteNode *nodeB = weldRU;
SKPhysicsBody *secondBody = nodeB.physicsBody;
weldRUHit = YES;
[self beginIntersectionWithBodyA:firstBody bodyB:secondBody];
}
if (!weldLDHit && [weldLD intersectsNode:[barriers objectAtIndex:i]]) {
SKSpriteNode *nodeA = (SKSpriteNode*)[barriers objectAtIndex:i];
SKPhysicsBody *firstBody = nodeA.physicsBody;
SKSpriteNode *nodeB = weldLD;
SKPhysicsBody *secondBody = nodeB.physicsBody;
weldLDHit = YES;
[self beginIntersectionWithBodyA:firstBody bodyB:secondBody];
}
it works for weldLD but not for weldRU.
I am experiencing the same problem with SKNode's intersectsNode: method. I think it has to do with a combination of anchor points and of two nodes not being children of the same parent node. The frame property is used to detect node intersection, and Apple defines the frame property of SKNode as "A rectangle in the parent’s coordinate system..." Thus with different parents you have different coordinate systems. Either way, my solution is to use this function instead.
bool CGRectIntersectsRect (
CGRect rect1,
CGRect rect2
);
And just make sure you have the correct coordinate system. Hint: use SKNode's convertPoint:FromNode: method.
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.