I have a Class with a SpriteNode that rotates very wide, when rotated within the main Scene(as if the anchor point is in the middle of the screen and the Sprite is rotating around it). I want it to rotate around the anchor point of itself in the main Scene(anchor point on the Sprite).
So in the Class i have something like the following
- (void)createChainWithPos:(CGPoint)pos {
SKTexture *myTex...
SKTexture *myTex2...
SKSpriteNode *chainFront = [SKSpriteNode spriteWithTexture:myTex];
chainFront.position = pos;
chainFront.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:mytex.size];
[self addChild:chainFront];
[_chainParts addObject:chainFront];
SKSpriteNode *chainSide = [SKSpriteNode spriteWithTexture:myTex2];
chainSide.position = CGPointMake(chainFront.position.x, chainFront.position.y - chainSide.size.height + 6);
chainSide.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:myTex2.size;
[self addChild:chainSide];
[_chainParts addObject:chainSide];
}
I have an loop creating the chain parts in the main file but couldn't get it rotate so stripped it down in an new project. There is actually 4 chain parts but i only did two. The other two are just mirrors of the ones above with their positions mirroring the chainSide.(to position them in a chain like fashion)
and in the Scene
self.chain1 = [chain node];
[self.chain1 createChainWithPos:CGPointMake(self.size.width/2, self.size.height/2);
self.chain1.zRotation = 3.14/4;
[self addChild:self.chain1];
I have a NSMutableArray in the chain class header that i use to hold the chains.
the physics joints
for (int i = 1; i < self.chain1.chainParts.count; i++ {
SKSpriteNode *nodeA = [[self.chain1 chainParts]objectAtindex:i-1];
SKSpriteNode *nodeB = [[self.chain1 chainParts]objectAtindex:i];
SKPhysicsJointPin *pin = [SKPhysicsJointPin jointWithBodyA:nodeA.physicsBody
bodyB:nodeB.physicsBody
anchor:CGPointMake(CGRectGetMidX(nodeA.frame), CGRectGetMinY(nodeA.Frame))];
}
I found that if i set the position of the chain in the middle in the Class, it rotates correctly in the Scene. However, the physics joints just start moving randomly across the screen and isn't correct to the anchor points set. (the physics joints are set in the Scene)
I don't know if i have to convert the coordinates or play with random anchor point positions , but if someone could shed some light if would be greatly appreciated.
You do not want to use the nodes frame, you want to use the nodes size, the frame mid is the screen coordinate + the fitted node size / 2, you want the middle of your sprite only, also for pi / 4 use M_PI_4
Related
I have an interesting problem. I create an SKSpriteNode with associated physics body.
SKTexture *shipTexture = [SKTexture textureWithImageNamed:#"Spaceship"];
self.heroSpriteNode = [HeroSpriteNode spriteNodeWithTexture:shipTexture size:CGSizeMake(40, 35.2)];
self.heroSpriteNode.physicsBody = [SKPhysicsBody bodyWithTexture:shipTexture size:CGSizeMake(40, 35.2)];
self.heroSpriteNode.physicsBody.dynamic = YES;
self.heroSpriteNode.physicsBody.mass = 1000.0;
self.heroSpriteNode.physicsBody.affectedByGravity = NO;
self.heroSpriteNode.physicsBody.allowsRotation = YES;
self.heroSpriteNode.physicsBody.angularDamping = 0.5;
self.heroSpriteNode.anchorPoint = CGPointMake(0.5,0.5);
self.heroSpriteNode.physicsBody.categoryBitMask = heroCategory;
self.heroSpriteNode.physicsBody.contactTestBitMask = groundCategory;
self.heroSpriteNode.physicsBody.collisionBitMask = groundCategory | edgeCategory;
The Scene itself has no gravity.
In the update routine I call applyTorque: to the physics body.
-(void) updateWithDeltaTime:(NSTimeInterval)seconds
{
CGFloat rotateTorque = self.rotateRate;
switch (self.rotateForceApplied)
{
case leftForceApplied:
break;
case rightForceApplied:
rotateTorque = -1.0 * rotateTorque;
break;
case zeroForceApplied: // separate from default in case behavior should change
rotateTorque = 0.0;
break;
default:
rotateTorque = 0.0;
break;
}
NSLog(#"before physics position: x %f, y %f", self.heroSpriteNode.position.x, self.heroSpriteNode.position.y);
[self.heroSpriteNode.physicsBody applyTorque:rotateTorque];
NSLog(#"after physics position: x %f, y %f", self.heroSpriteNode.position.x, self.heroSpriteNode.position.y);
}
The sprite rotates and appears to rotate in place. What it is actually doing is rotating around a center point (so no net lateral movement). This is seen by logging the sprite position before and after applying the torque. No other actions are being applied to the physics body. The movement in position is about 9 points in each direction at most.
Because the camera is pinned by constraints to the "hero" sprite, and the world moves with the camera (the centerOnNode: sample code), this causes the whole world to move in a circular pattern as the sprite spins. The world itself does not spin but moves at the same rate in a circular pattern with the spinning.
With the sprite anchorPoint being 0.5, 0.5 I would think it should rotate around a center point which should not change the position of the sprite.
What would I being doing wrong with this?
If it matters this is on iOS9, Xcode7, running on device not in the simulator. (The iOS9 SpriteKit documentation is publicly available on Apple's website, as is a public beta of iOS9 itself so this should not be breaking any NDA, and I don't think anything here is iOS9 specific anyway)
Sprite Kit is a physics engine that attempts to mimic characteristics of objects in the real world, so you should expect an object with a physics body in the simulation to behave as they would in nature. In this case, you are rotating a non-uniform physics body that may rotate non-uniformly and, possibly, move over time (unless the body is rotating about its center of mass). If you change the physics body to a circle, the sprite should rotate uniformly and should remain at a fixed location.
Hi I have a bunch of round SKSpriteNodes with a circle physical body. Now when these balls roll down a path I want some of these SKSpritenodes image to stay upright even when rolling. So think of an arrow pointing upwards. When the ball starts rolling the arrow spins in circles. But for some balls Id like the arrow to remain pointing up even when the ball rolls. Whats the best way of doing this?
Edit
So an answer was given but from testing it turns out it is not the correct one. Not allowing the ball to rotate affects the way it rolls down the path. So I guess what I want is rotation to be on but the image to always appear to the user like its not rotating. Thanks.
This looks like a job for SupermSKConstraint. Constraints are evaluated and applied after the physics simulation runs on each frame, so you can use them for tasks like making a node point a certain direction regardless of what physics does to it. For this, you'd want a zRotation constraint.
But there's a bit more to it than that. If you set a zero-rotation constraint on the ball:
// Swift
let constraint = SKConstraint.zRotation(SKRange(constantValue: 0))
ball.constraints = [constraint]
You'll find that SpriteKit resets the physics body's transform every frame due to the constraint, so it only sort-of behaves like it's rolling. Probably not what you want. (To get a better idea what's going on here, try adding a zero-rotation constraint to a rectangular physics body in a world without gravity, applying an angular impulse to it, and watching it try to spin in a view with showsPhysics turned on. You'll see the sprite and its physics body get out of sync and shake a bit -- probably due to accumulated rounding errors as the physics engine and the constraint engine fight it out.)
Instead, you can do a bit of what's in 0x141E's answer, but use constraints to make it less code (and run more efficiently):
Give the ball node a circular physics body. (And possibly no texture, if the only art you want for the ball is a non-rotating sprite.)
Add the arrow node as a child of the ball node. (It doesn't need its own physics body.)
Put a zero-rotation constraint on the arrow.
Wait, that doesn't work -- I told the arrow to not rotate, but it's still spinning?! Remember that child nodes are positioned (and rotated and scaled) relative to their parent node. So the arrow isn't spinning relative to the ball, but the ball is spinning. Don't worry, you can still solve this with a constraint:
Tell the constraint to operate relative to the node containing the ball (probably the scene).
Now the constraint will keep the arrow in place while allowing the ball to rotate however the physics simulation wants it to.
Here's some test code to illustrate:
// Step 1: A rectangular spinner so we can see the rotation
// more easily than with a ball
let spinner = SKSpriteNode(color: SKColor.redColor(), size: CGSize(width: 300, height: 20))
spinner.position.x = scene.frame.midX
spinner.position.y = scene.frame.midY
spinner.physicsBody = SKPhysicsBody(rectangleOfSize: spinner.size)
scene.addChild(spinner)
spinner.physicsBody?.applyAngularImpulse(0.1) // wheeeeee
// Step 2: Make the arrow a child of the spinner
let arrow = SKSpriteNode(color: SKColor.greenColor(), size: CGSize(width: 20, height: 50))
spinner.addChild(arrow)
// Step 3: Constrain the arrow's rotation...
let constraint = SKConstraint.zRotation(SKRange(constantValue: 0))
arrow.constraints = [constraint]
// Step 4: ...relative to the scene, instead of to its parent
constraint.referenceNode = scene
Here are two methods to create a ball with a physics body and an arrow:
Add an arrow as a child of a ball
Add both the ball and the arrow directly to the scene
Here's what will happen when you add the above to the SpriteKit simulation:
The arrow will rotate when the ball rotates
Both the arrow and the ball will move/rotate independently
If you want the arrow to rotate with the ball, choose Option 1. If you want the arrow to remain fixed, choose Option 2. If you choose Option 2, you will need to adjust the rotation of the arrow to ensure that it points upward. Here's an example of how to do that.
-(void)didMoveToView:(SKView *)view {
self.scaleMode = SKSceneScaleModeResizeFill;
/* Create an edge around the scene */
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:view.frame];
// Show outline of all physics bodies
self.view.showsPhysics = YES;
CGFloat radius = 16;
SKNode *balls = [SKNode node];
balls.name = #"balls";
[self addChild:balls];
// Create 5 balls with stationary arrows
for (int i = 0;i<5;i++) {
// Create a shape node with a circular physics body. If you are targeting iOS 8,
// you have other options to create circular node. You can also create an SKSpriteNode
// with a texture
SKShapeNode *ball = [SKShapeNode node];
// Create a CGPath that is centered
ball.path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(-radius,-radius,radius*2,radius*2)].CGPath;
ball.fillColor = [SKColor whiteColor];
ball.position = CGPointMake(100, 100+i*radius*2);
ball.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:radius];
[balls addChild:ball];
// Create an arrow node
CGSize size = CGSizeMake(2, radius*2);
SKSpriteNode *arrow = [SKSpriteNode spriteNodeWithColor:[SKColor blackColor] size:size];
arrow.name = #"arrow";
arrow.position = CGPointZero;
[ball addChild:arrow];
// Apply angular impulse to the ball so it spins when it hits the floor
[ball.physicsBody applyAngularImpulse:-1];
}
}
- (void) didSimulatePhysics
{
SKNode *balls = [self childNodeWithName:#"balls"];
for (SKNode *ball in balls.children) {
SKNode *arrow = [ball childNodeWithName:#"arrow"];
arrow.zRotation = -ball.zRotation;
}
}
sprite.physicsBody.allowsRotation = NO;
The allowRotation property should control exactly what you are asking.
I am creating a simple Sprite Kit game however when i am adding the PhysicsBody to one of my sprites it seems to be going in the wrong position. i know that it is in the wrong position as i have have set
skView.showsPhysics = YES;
and it is showing up in the wrong position.
The Square in the bottom corner is the physics body for the first semicircle. I am using a square at the moment just for testing purposes.
My app includes view following and follows my main sprite when it moves. I implemented this by following apples documentation and creating a 'myworld' node and creating all other nodes from that node.
myWorld = [SKNode node];
[self addChild:myWorld];
semicircle = [SKSpriteNode spriteNodeWithImageNamed:#"SEMICRICLE.png"];
semicircle.size = CGSizeMake(semicircle.frame.size.width/10, semicircle.frame.size.height/10);
semicircle.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:semicircle.frame.size];
semicircle.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
semicircle.physicsBody.dynamic = YES;
semicircle.physicsBody.collisionBitMask = 0;
semicircle.name = #"semicircle";
[myWorld addChild:semicircle];
To centre on the node I call these methods
- (void)didSimulatePhysics
{
[self centerOnNode: [self childNodeWithName: #"//mainball"]];
}
- (void) centerOnNode: (SKNode *) node
{
CGPoint cameraPositionInScene = [node.scene convertPoint:node.position fromNode:node.parent];
node.parent.position = CGPointMake(node.parent.position.x - cameraPositionInScene.x, node.parent.position.y - cameraPositionInScene.y);
}
I don't know if the my world thing makes any difference to the SkPhysics body...
SKPhysicsBody starts at coordinates 0,0 which is at the bottom left hand corner. If you make the area smaller, as you did by width/10 and height/10, you decrease the size but from the bottom left.
I think what you are looking for is bodyWithRectangleOfSize:center: which allows you to manually set the center from which you base your physics body area on.
Update:
Based on what I understand, your smallest semi circle pic size is the same as the screen size. I would suggest you modify the image size to something like the example I have. You can then set the sprite's position as required and set the physics body to the half of the image containing your semi circle.
Your centerOnNode call should be put in the didEvaluateActions function instead of the didSimulatePhysics function. This is because you need to move the world before the physics are drawn so that they stay in sync. Similar question found here: https://stackoverflow.com/a/24804793/5062806
I am trying to create a conveyor belt effect using SpriteKit like so
MY first reflex would be to create a conveyor belt image bigger than the screen and then move it repeatedly forever with actions. But this does not seem ok because it is dependent on the screen size.
Is there any better way to do this ?
Also obviously I want to put things (which would move independently) on the conveyor belt so the node is an SKNode with a the child sprite node that is moving.
Update : I would like the conveyor belt to move "visually"; so the lines move in a direction giving the impression of movement.
Apply physicsBody to all those sprites which you need to move on the conveyor belt and set the affectedByGravity property as NO.
In this example, I am assuming that the spriteNode representing your conveyor belt is called conveyor. Also, all the sprite nodes which need to be moved are have the string "moveable" as their name property.
Then, in your -update: method,
-(void)update:(CFTimeInterval)currentTime
{
[self enumerateChildNodesWithName:#"moveable" usingBlock:^(SKNode *node, BOOL *stop{
if ([node intersectsNode:conveyor])
{
[node.physicsBody applyForce:CGVectorMake(-1, 0)];
//edit the vector to get the right force. This will be too fast.
}
}];
}
After this, just add the desired sprites on the correct positions and you will see them moving by themselves.
For the animation, it would be better to use an array of textures which you can loop on the sprite.
Alternatively, you can add and remove a series of small sprites with a sectional image and move them like you do the sprites which are travelling on the conveyor.
#akashg has pointed out a solution for moving objects across the conveyor belt, I am giving my answer as how to make the conveyor belt look as if it is moving
One suggestion and my initial intuition was to place a larger rectangle than the screen on the scene and move this repeatedly. Upon reflecting I think this is not a nice solution because if we would want to place a conveyor belt on the middle, in a way we see both it ends this would not be possible without an extra clipping mask.
The ideal solution would be to tile the SKTexture on the SKSpriteNode and just offset this texture; but this does not seem to be possible with Sprite Kit (no tile mechanisms).
So basically what I'm doing is creating subtextures from a texture that is like so [tile][tile](2 times a repeatable tile) and I just show these subtextures one after the other to create an animation.
Here is the code :
- (SKSpriteNode *) newConveyor
{
SKTexture *conveyorTexture = [SKTexture textureWithImageNamed:#"testTextureDouble"];
SKTexture *halfConveyorTexture = [SKTexture textureWithRect:CGRectMake(0.5, 0.0, 0.5, 1.0) inTexture:conveyorTexture];
SKSpriteNode *conveyor = [SKSpriteNode spriteNodeWithTexture:halfConveyorTexture size:CGSizeMake(conveyorTexture.size.width/2, conveyorTexture.size.height)];
NSArray *textureArray = [self horizontalTextureArrayForTxture:conveyorTexture];
SKAction *moveAction = [SKAction animateWithTextures:textureArray timePerFrame:0.01 resize:NO restore:YES];
[conveyor runAction:[SKAction repeatActionForever:moveAction]];
return conveyor;
}
- (NSArray *) horizontalTextureArrayForTxture : (SKTexture *) texture
{
CGFloat deltaOnePixel = 1.0 / texture.size.width;
int countSubtextures = texture.size.width / 2;
NSMutableArray *textureArray = [[NSMutableArray alloc] initWithCapacity:countSubtextures];
CGFloat offset = 0;
for (int i = 0; i < countSubtextures; i++)
{
offset = i * deltaOnePixel;
SKTexture *subTexture = [SKTexture textureWithRect:CGRectMake(offset, 0.0, 0.5, 1.0) inTexture:texture];
[textureArray addObject:subTexture];
}
return [NSArray arrayWithArray:textureArray];
}
Now this is still not ideal because it is necessary to make an image with 2 tiles manually. We can also edit a SKTexture with a CIFilter transform that could potentially be used to create this texture with 2 tiles.
Apart from this I think this solution is better because it does not depend on the size of the screen and is memory efficient; but in order for it to be used on the whole screen I would have to create more SKSpriteNode objects that share the same moveAction that I have used, since tiling is not possible with Sprite Kit according to this source :
How do you set a texture to tile in Sprite Kit.
I will try to update the code to make it possible to tile by using multiple SKSpriteNode objects.
With SpriteKit, is it possible to have two nodes that collide with one another, but then when another node is introduced, have how the physics works change?
For example, consider the following 3 nodes:
- Object
- Object_Hole
- Player
So, a scene containing a Player (orange circle) and an Object (blue rect):
In the above scene, the Player (circle) would be affected by gravity and collide with the Object (square). I know how this works by using the physics body, category and collision bitmasks.
Now, introduce the Object_Hole (green square):
In the above scene, the Object_Hole (green square) overlays the Object (blue rect) - this can be on either the same z plane or a higher plane.
Is it possible to make the physicsBody on the Player (circle) not collide with the Object in the area that the Object_Hole is?
If there's a better way to achieve this than adding an overlaying Node, please let me know. Otherwise, is it possible?
Thanks!
You could look into using categoryBitMask and collisionBitMask:
https://developer.apple.com/library/ios/documentation/SpriteKit/Reference/SKPhysicsBody_Ref/Reference/Reference.html#//apple_ref/occ/instp/SKPhysicsBody/collisionBitMask
If you want your ball to collide with the object, but not some hole in the object, you will probably want to break your object into 2 pieces with an actual hole in the middle. Set the hole sprite's categoryBitMask and collisionBitMask to be completely different from those of the object and ball.
// sprite1 and sprite2 will never collide.
SKSpriteNode *sprite1 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(20.0f, 10.0f)];
sprite1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:sprite.size];
sprite1.physicsBody.collisionBitMask = 0xffff0000;
sprite1.physicsBody.categoryBitMask = 0xffff0000;
SKSpriteNode *sprite2 = [SKSpriteNode spriteNodeWithColor:[UIColor blueColor] size:CGSizeMake(20.0f, 10.0f)];
sprite2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:sprite.size];
sprite2.physicsBody.collisionBitMask = 0x0000ffff;
sprite2.physicsBody.categoryBitMask = 0x0000ffff;
Create the blue bar as 2 separate objects, with a gap between them of 0 points (or even overlapping slightly in case the point where they touch causes odd physics reactions) when the 'hole' isn't around, but with a 'hole-sized' gap between them when the hole is preset.