The gear joint in Box2d is great, but I don't know how to implement that in Sprite Kit. Is there any solutions to implement the gear joint in Sprite Kit?
Thanks.
Here are the available Sprite-Kit joints :https://developer.apple.com/reference/spritekit/skphysicsjoint
As far as I can understand, there does not appear to be a direct correlation to Box2D's gear joint, which seems to make one body rotate when another body is rotated.
In that case, you might want to investigate overriding the didSimulatePhysics or didFinishUpdate methods to manually set the rotation of one object based upon the rotation of another object:
https://developer.apple.com/reference/spritekit/skscene/1519965-didsimulatephysics
https://developer.apple.com/reference/spritekit/skscene/1520269-didfinishupdate
It might be as simple as:
wheel2.zRotation = wheel1.zRotation
but if the gears have different numbers of teeth (thus different ratios), you'll have to do some calculations.
Related
I want to write a simple top down racing game for iOS. I want to use Sprite Kit instead Cocos2D , I'm new to game development and I have a question:
How can I create the race tracks? What I think is: One single big background image for each track and a car that moves over it and remains inside the track by interaction with a path. The path is inserted by a coordinate system in the level code and represents the "borders" of the road.
Is this a good way to start a top down racing game? Or are there better ways? How can I "draw" the path over my background image?
You can use "Tiled Map Editor" http://www.mapeditor.org/ to create your maps. I'm thinking you'll only need a few unique tiles, one for straight track, one for grass, one for curved track, maybe some trees, etc.
As for the path, you can try to use an polygonal edge physics body? And then move the car to where the user touches on the screen. if the user tries to move the car outside, the car will bump against the physics body of the edge.
I'm currently making a game where driving a moon lander across the terrain of alien planets. The lander is free moving so you can turn any direction you like.
I've got a camera centred on the player's vehicle and navigation is working well, however...
As the player approaches the horisontal sides (x) of the map I'd like the map to display continuously.
I've used a couple of different approaches so far; I've added an identical sprite as the map to the left of the map and created a method that moves the extended map to the right side if you approach that side instead, and I've also tested with two different extended maps, one for left and one for right. I've then setup physics for the extended maps and changed the landers position from one side of the map to the other as it collides with the extended maps.
My issue is that I'd like to have my enemies spawning and walking around the main map and as you approach the side you will of course not see the enemies on the other side of the map - you'd only see the extended map with no contents.
My preference would be for the world to "bend" so that as you approach the left edge you'd automatically see the right edge and vice versa. I have no idea whether this is even feasible so any suggestions are much appreciated.
Thanks in advance.
I'm not sure I understand your question. Maybe this will further discussion, anyhow.
If you are looking for a scrolling behavior then I would have two backgrounds (or more if you want a wider scrolling field) and your method for swapping the tiles around to make the background feel continuous, use the "camera" tracking technique and shown in Apple's sprite kit demo to follow your player (which it sounds like you are doing). Then when aliens move offscreen in either direction relocate them in the same way that you would swap out your background tile(s) with something like position.x += widthOfBackgroundTile.
I have a SpriteKit Scene in which I want to have the effect as if a camera zoom and scale. Does anyone know of any libraries or some easy methods of doing this?
It was very easy to do in other 2D engines but does not seem simple.
I was thinking of doing it from the app delegate, and using the window to zoom since my character does stay around the same position.
The desired effect I would like to accomplish is like that of the start of an Angry Bird level when the camera pans into the level and then the launch doc.
http://www.youtube.com/watch?v=_iQbZ3KNGWQ This is an example of the camera zoom and pans I am talking about.
Thanks for the help.
If you add an SKNode to the SKScene, and make your scene content children of that node instead of direct children of the scene, then you can zoom and pan all of the contained content just by adjusting the xScale, yScale and position properties of the added node. (Any content you did not want scrolled e.g. scores or whatever could then be added to a different SKNode or added directly to the scene).
The adjustment could be done by overriding one of update:, didEvaluateActions, or didSimulatePhysics in your SKScene subclass. The choice would depend on if you are just moving your character around by yourself in update:, or if it also gets moved around by running SKActions or by simulated physics.
I'm working on a game in which the user should be able to trigger 'rods' that come out from the edge of the screen to displace elements on screen (balls). These projectiles roughly resemble pool-cues. Or perhaps pinball plungers, except that they start from the 'loaded' position (mostly offscreen), and when triggered, they eject out, then quickly retreat.
I'm unclear how I should build these with Sprite Kit.
The game uses the PhysicsEngine, and the onscreen balls should be effected both by gravity AND they should be displaced when they collide with the rods. However the rods should neither be effected by gravity, not displaced when they collide with the balls -- they should simply retreat regardless of whether they've made contact with the balls.
I realize I can set the affectedByGravity property for the rods. However because they will still displace slightly when they collide with the balls. How can I 'fix' or 'peg' them in place? Do I need to use an SKPhysicsSlidingJoint? If so, has anyone encountered any examples online? Is there a simpler way to do this?
A related physics engine, Box2D distinguishes static, kinematic, and dynamic bodies.
Kinematic bodies can move and will collide with other objects, but they are themselves not affected by dynamic bodies or forces like gravity. Thus, consider setting rod.dynamic = NO; but animate it with actions. See also here in the reference for SKPhysicsBody.
I'm pretty new to Box2D and cocos2d. I'm trying to do something which I thought would be pretty simple, but it is turning out to be more difficult than I had expected and I cannot find a working answer anywhere.
Basically, I want to move a b2body and rotate it to a certain point with animation.
I can get it to the correct position and rotation with:
targetBody->SetTransform(b2Vec2(10.0f,1.0f),10);
But I have no idea how to animate it there over time. I tried using cocos2d animation on the sprite used for the body, but that doesn't do anything. Any ideas?
There are a couple of ways you could do this.
You could use SetTransform every time step to update the position of the body gradually over time, in effect performing the animation yourself. The drawback with this method is that the body is 'teleporting' to the new position rather than moving, so it has no momentum, which means you can get odd results if it hits anything along the way. Still, if you know it will not hit anything or does not need to react to a collision this would be ok.
The other way is to SetLinearVelocity and SetAngularVelocity to give the body proper movement. This will keep the results of a collision realistic, and you don't need to keep updating anything every timestep. On the other hand, you will need to detect when the body has arrived at the desired position and then set the velocities back to zero, otherwise it will just keep moving. For dynamic bodies you will also need to counter gravity somehow, either by setting the gravity scale of the body to zero, or by applying an upwards force to balance gravity, or by changing the body type to kinematic during the move.
In general, you use Box2D to simulate the physical behavior of objects in relation to each other. The rules of mechanics implemented by Box2D dictate how your cocos2d CCSprites move if you continuously update the translation and rotation of your sprites according to their corresponding Box2d b2Body. You will have some kind of repeatedly invoked tick: method in which you step your Box2d world along in time, and in which you update your sprite positions according to simulation results of Box2d.
This pattern corresponds to b2Bodys of type b2_dynamicBody. Physical laws dictate the motion of the body in this case, and your sprites will follow these simulation results. This is why setting a conflicting position of a sprite by means of a CCAction or even directly will be undone almost instantaneously with the next tick:.
Solution 1: kinematic body type
However, there do exist other modes for a b2Body, and one of these is b2_kinematicBody in which the translation is no longer governed by the world but by the velocities or angular speeds you dictate through setters. So it would be one solution to work with body type b2_kinematicBody as in:
b2BodyDef bdef;
bdef.type = b2_kinematicBody;
With this you would manipulate the velocity and angular speed of a b2Body explicitly. In this case, Box2d is still responsible for moving bodies around, but according the velocities you dictate, and without any force effects of collision or gravity applied to this particular body. Also with this strategy, your CCSprites will follow b2Bodys. Setting conflicting positions for your sprites directly or by applying a CCAction would not make sense for the same reason as described above.
Solution 2: decouple sprites from Box2d
An alternative way to animating sprites would be to fully decouple those sprites from Box2d. In this case, you would simply not have any b2Body that governs the position of the sprite you are going to animate. Now, in this case, only you will dictate the position and rotation of your CCSprite, i.e. directly either through its position property or by applying a CCAction.