I am building a game where the player sprite bounces around the GameScene. When the user taps the screen, the player sprite should stick to the next wall it hits. How can I completely remove all the energy from the sprite so that it no longer moves?
What attributes should I change? I have tried setting:
restitution() = 0
but this does not help.
I am looking for an answer for SpriteKit in Swift.
Thanks for any help.
You are talking about a node's velocity. It's dx and dy values to be exact.
yourNode.physicsBody?.velocity = CGVectorMake( 0, 0 )
the above will set your node's x and y axis velocity to zero.
Related
I am building an endless runner game where platforms appear at random intervals and then scroll right to left across the screen.
I have a sprite that jumps up vertically using
- (void)makeCharacterJump {
[self.spriteCaveman.physicsBody applyImpulse:CGVectorMake(0.0f, 80.0f)];
}
The problem is that the effect of gravity on the sprite means that it falls quite quickly and cant make the gap between the platforms.
What I would like to do is slightly slow down the effect of gravity on the falling sprite so it creates the impression of slightly floating down.
Any ideas?
If the character is the only node affected by gravity then you can change the scene’s gravity with:
self.physicsWorld.gravity = CGVectorMake(0, desiredGravity);
If it is not then you’ll have to play with the character’s physics body properties: friction, linearDamping or angularDamping values.
Hope that helps.
I am developing a game with swift Sprite kit. But I've got a problem, as you can see in the picture I have a number of physical blocks with the same size aligned. When I slide this block above the others sometimes he gets stuck or do small jumps.
It seems that the physical bodies sometimes overlap.
Anyone know how I can fix it to have a continuous and without inprecision movement?
Some physics characteristics:
player.physicsBody?.friction = 0.0
player.physicsBody?.restitution = 0.00
player.physicsBody?.linearDamping = 0.1
player.physicsBody?.angularDamping = 0.0
player.physicsBody?.allowsRotation = false
player.physicsBody?.velocity.dx = 0
player.physicsBody?.velocity.dy = 0
player.physicsBody?.categoryBitMask = heroCategory
player.physicsBody?.contactTestBitMask = enemyCategory
player.physicsBody?.density = 2.3
The problem appears to be just a slight imperfection of physics engine (and hey, it's a simulation, and not completely accurate, I've run into this kind of thing before). I see that you are preventing rotation of the player, so you can change the physics body of the square player into a circle. This should be something like:
player.physicsBody = SKPhysicsBody(circleOfRadius: 10)
Replace 10 with the proper radius of your player. This should smooth out the bumps you are encountering.
How are you sliding the block?
I've had the same problem and I was able to solve it sliding my hero using SKAction to run a code block that changes the hero's velocity or by just simple running an SKAction.moveBy. Your SKAction should'nt be attempting to push your block against the ground. An action to move the block only in the x direction.
You can also smooth the surface by making sure your physicsBody(s) of ground blocks are not overlapping. Introduce a gap of 1-2 points. Or maybe group tiles with a single physicsBody. This may help as well.
I am creating a tilemap platform game in SpriteKit. I assigned collision paths to the physics body of all ground tiles and made them non-dynamic. To the player I assigned two collision polygons: a circle on the bottom and a rectangle on the top.
The player sprite has a fixed position on screen, while the level is scrolling from right to left. Now, as long as the player sprite is on flat ground, the collisions work perfectly and the player is walking on the ground. However, I also have some sloped terrain tiles that I want the player to follow (e.g. walking uphill). But when the player reaches a sloped tile, he simply bounces off of it, being unable to "climb" it.
Similarly, when I drop the player from above on a sloped tile, he slides down the "hill", instead of remaining in position.
I have both restitution and friction set to 0.
So how can I make the player sprite follow the ground regardless of its shape and how can I make the player stay on a sloped tile instead of sliding down?
I tried using SKConstraints with positionX set to a constant value. At first it seemed to work, but then the player got stuck in the middle of a sloped tile and eventually fell through it.
I also tried different shapes of collision polygons on the player (e.g. a rectangle instead of a circle at the bottom) but that changed nothing.
Any help is appreciated!
This has more to do with your game logic instead of your map properties. You need to have several "states" for your player. For example, if your player is idle you can set the CGVector to 0,0. This will stop the player from moving in any direction.
To give you some examples on movement. Let's say you want to make your object move right:
// move node's physics body to the right while leaving vertical movement as is
// 160 is just an example
myNode.physicsBody.velocity = CGVectorMake(160, self.physicsBody.velocity.dy);
// do not allow right movement to exceed 160
if(myNode.physicsBody.velocity.dx > 160)
myNode.physicsBody.velocity = CGVectorMake(160, self.physicsBody.velocity.dy);
To move left you inverse the dx value:
myNode.physicsBody.velocity = CGVectorMake(-160, self.physicsBody.velocity.dy);
if(myNode.physicsBody.velocity.dx < -160)
myNode.physicsBody.velocity = CGVectorMake(-160, self.physicsBody.velocity.dy);
Allow myNode to be affected by gravity and it should remain in contact with the ground as it moves down a slope.
It's a tilemap platform game...
Then gravity isn't important, put gravity to a very low value and then change all your impulses for the jumps and such in relation to the change in gravity...
OR,
Possibly, if the game isn't randomly generated you can set up a uibezierpath, and turn the path off if he stops moving up the hill.
But then if he stopped mid-hill or was starting from the top, he would still slide down...
And increasing friction (not setting it to 0) may help. Try friction at 1?
This seems to be a major oversight by Apple, but since SKPhysicsJoints have their anchor points set in Scene coordinates, this makes doing any kind of scrolling game impossible.
To simulate a camera in SpriteKit you create a WorldNode which contains all of the gameplay elements, and then pan that around the scene. Unfortunately, doing this causes the Scene coordinates of every object in the game to change on every frame as you pan the world around. In turn, this breaks the joint anchor points, and things go berserk.
There isn't even a way to change the joint's anchor point, so I don't even have a way of just updating the coordinate every frame. It would seem that using SKPhysicsJoint in a scrolling game is not an option.
Does anyone know of a way around this?
Ok, I think I figured out what was going on, and I was totally incorrect in my original assumption. The reason my anchor points looked incorrect is because the [convertPoint toNode] call was returning me Scene coordinates that were incorrect. After several hours I realized it was off by exactly half the screen dimensions. My Scene has an anchorPoint of (0.5, 0.5), but this screws up the conversion values. So, if I simply offset the point by width/2, height/2 it's correct:
GPoint pt = CGPointMake(anchorWorldX, anchorWorldY);
pt = [gGameScene convertPoint:pt fromNode:gGameWorld]; // convert to scene coords, but it's WRONG
pt.x += scene.size.width * scene.anchorPoint.x; // this properly adjusts the value to be correct
pt.y += scene.size.height * scene.anchorPoint.y;
SKPhysicsJointPin* pin =[SKPhysicsJointPin jointWithBodyA:hinge.physicsBody bodyB:door.physicsBody anchor:pt];
I have working implementation of drag and drop feature written in Cocos2d + Box2d for iOS. I need to port it to Sprite Kit. The logic is pretty basic:
when user touching the screen, find sprite under the finger
create mouse joint between found sprite and the scene's physics body, set joint's target to position of touch
when touches moved, update joint's target to new position
when touches ended, remove the joint
Everything is working quite well. I like the way physics is simulated when touches ends - the dragged shape has velocity dependent on dragging speed and direction, so when I left my finger from the screen while moving the sprite, it will continue moving in the same direction, but now affected by gravity and damping.
Unfortunately, I'm not able to reproduce the same effect using Sprite Kit. There is no such joint like mouse joint, but I have tried using other joint types. I almost succeeded with SKPhysicsJointFixed - I'm creating new sprite and joint between it and dragged sprite, when touches moving I'm moving the newly created sprite. Unfortunately it doesn't work like mouse joint in Cocos2d + Box2d - while dragging the sprite, its velocity always equals zero. So, every time I left my finger from the screen, the dragged sprite stops immediately and start falling affected by gravity. No matter how fast I move the finger when dragging, after releasing dragged shape, it behaves exactly the same way.
My question is how to implement mouse joint in Sprite Kit, or how to implement drag and drop feature that works like described above?
Update:
This is a box2d mouse joint example that could give you more clear view on what I am trying to implement using Sprite Kit:
http://blog.allanbishop.com/wp-content/uploads/2010/09/Box2DJointTutorial1.swf
I'm pretty new to iOS development so I guess this might not be the best way, but this is how I solved it and it seems to work pretty smooth actually.
I'm using a UIPanGestureRecognizer to handle the touch event. I set this one up in my didMoveToView: with this code:
UIPanGestureRecognizer *gestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handlePan:)];
An UIPanGestureRecognizer is passed to handlePan: and I check with recognizer.state == UIGestureRecognizerStateEnded if the touched stopped. This is where I want to "release" the object and "let it fly away". For doing so I needed to calculate a few things, first of all I get the velocity of the finger/touch with this code:
CGPoint velocity = [recognizer velocityInView:recognizer.view];
(I use the same method (handlePan:) with other statements for getting the right object when touch starts, and letting the object be under the finger all the time by setting the position of the object to the location of the touch when moving)
Now I know the velocity, but I still don't know how much force I need to apply to the object. You should be able to calculate the force by this formula: Force = mass * acceleration. We know the mass (object.physicsBody.mass) and we know the velocity. To get the acceleration we need the time as well because acceleration = velocity / time.
In my update: method that is called every time a new frame is to be rendered I calculate the difference between the last time a frame was about to be rendered by doing something like this:
self.delta = currentTime - self.lastTime;
self.lastTime = currentTime;
I now can calculate which force that is needed to get the object moving in the velocity I'm "dragging it in". To do this I do the following:
[self.currentNode.physicsBody applyForce:CGVectorMake(velocity.x/self.delta * self.currentNode.physicsBody.mass, -velocity.y/self.delta * self.currentNode.physicsBody.mass)];
I take velocity divided with the difference in time since last frame (self.delta) to get the acceleration, and then multiply it with the mass of the object to get the force needed to keep (or actually getting) the object moving in the same direction and in the same velocity as it was moved by my finger.
This is working for me at the moment and I hope it helps other people too, and please tell me if I got something wrong or if there is a better solution. So far I have not found any "native solution".
If the only issue is velocity, then that is simple to fix.
Subtract the current touch position from the previous touch position to get the velocity between the last and current touch. Use applyForce: to apply this velocity to the body.
In order to prevent the body from moving on its own while dragging, read out the new velocity from the body after calling applyForce: and keep it in an ivar and set the body's velocity to zero.
When the touch ends, set the body's velocity to the one you keep as an ivar.
If this doesn't work, try using applyImpulse: and/or setting the velocity before calling any of the two methods, ie:
sprite.physicsBody.velocity = bodyVelocity;
[sprite.physicsBody applyForce:touchVelocity];
bodyVelocity = sprite.physicsBody.velocity;
sprite.physicsBody.velocity = CGVectorMake(0, 0);
That way you can keep the body's velocity without losing control over it while dragging.