I wonder if anyone can suggest the best approach to detect collision between multiple shapes.
I am using Chipmunk on an iPad with iOS 4.2 and Cocos2D 1.0 - I basically have a cpShape travelling around the iPad screen - there are two segment cpShape's (arranged in a V-shape) and I'd like to know when my travelling shape is touching BOTH the segment shapes (ie the corresponding sprite is sitting comfortably inside the V).
Any ideas? I have set up my callback with cpSpaceAddCollisionHandler but I don't seem to have a list of all of the shapes the current colliding shape is touching. Is that possible or do I have to code and store the information manually?
Thanks
i think your going to have to store some data in your sprite object.
There are callbacks in chipmunk for when 2 objects first touch, and then they part.
Begin: Two shapes just started touching for the first time this step. Return true from the callback to process the collision normally or false to cause Chipmunk to ignore the collision entirely. If you return false, the pre-solve and post-solve callbacks will never be run, but you will still recieve a separate event when the shapes stop overlapping.
Separate: Two shapes have just stopped touching for the first time this step.
You could make your object that is to 'sit within the V' have a 2 bool's one for each side of the V, make it true when they 'begin' and false when they separate.
If they are both true, and the object isSleeping (stop moving) (i come from a box2d background, not sure the chipmunk equivalent is).
Hope that helps.
Related
I am currently working on a 2D endless runner, written in Swift3 and using Spritekit.
Short question:
Is there a way to only check for collisions on the right side of my character's rectangular physics body?
More info:
The platform on which the character runs is made of puzzle pieces and the user builds upon it as the game progresses. The character progresses left to right, in respect to the background (which goes right to left).
I want the character to automatically jump when he collides with a piece on his right side. However, any pieces that the player puts to the right of him (same Y value as the character) is of the same class as the pieces underneath him.
So the same code that checks for collision between the character and pieces to his right, and make him jump, will also make him jump as long as the game detects collision between the character and the pieces under him.
I have not been able to find another problem like mine, since usually others' characters are colliding with objects of different classes from their ground class.
Thanks!
P.S. I have tried to make my character a SKSpriteNode with two physics bodies, but I could not find any helpful documentation. If it helps any, my character also performs a looping running animation--though I can't imagine that would harm anything.
You could achieve that by detecting collisions with your rectangle and then deciding whether the collision was with the side of your interest or not. Here is a discussion about how to do that. Good luck!
Have you tried adding a non visible sub node (e.g. feetNode) to your character's sprite node and giving that sub node the physics body (class) for floor contact ?
Depending on the rest of your logic, it may allow you to use a different physics class for your character have more flexibility in collision detection.
In fact, you could probably use that approach with several sub nodes in your character's sprite node and have multiple collision behaviours for the character depending on what hits it.
Once you obtain the contact point of the 2 bodies that are colliding, determine which body is the one that is colliding by checking the categorymasks and then check its CGPoints x position. This x position can be compared to the other body's x position to know exactly which side it is colliding from.
if Body A's x position > Body B's x position, Body A is on the right and if not, its on the left.
As simple as that.
Hope this helps!
I am making a Sprite Kit game where the player (basically a stickman) has a running animation and a parallax scrolling background.
Now I have enemies that come near my player. To destroy these enemies sometimes I have to touch the enemies node to launch a rocket or attack them with an attack button or just jump over them.
Everything is working fine, but I want to add some extra moves to destroy them. I want some enemies that you can just destroy if you have drawn a whole circle around them. So imagine they come and you make a circle and then my player launch a laser or something. The problem is I have no idea where to start.
I haven't found anything on the internet. If it's too complicated or almost impossible how about touching my player node and dragging to the enemy?
EDIT: I think I have to create a custom GestureRecognizer that recognizes if a circle is drawn around a sprite and then runs the code. I don't know how this works ?
Yes, it's too complex. Not just from a coding point of view, but also from that of the player's experience.
Anything that requires complex gestures over a large amount of glass is annoying for the player because they're never going to have the same experience. Their finger's moisture and oil content always changes, as does the ambient temperature and cleanliness of their screen.
So big gestures required to be performed quickly (a gaming input like this) will sometimes be fun and smooth, and other times degrade as an experience based on the nature of the above properties.
Best to avoid them for a game's best possible experience.
If you must do it, there's two ways to research how.
Seek out "custom gesture" creation and utilisation through documentation and google, etc.
Think about using some kind of array to store all the points where the player's finger moves through during that circle gesture and attempt to discern if an enemy is within that space and then act accordingly.
--- probably other ways, too. But these jump to mind.
I wrote few simple SpriteKit games and always had problems with strong collisions behaviour. Even now with my latest game in development the same issue appears quite randomly.
Game-play area is inside edgeLoopFromRect physics body
There are some objects (with circle physics body) bouncing around
But sometimes (this happens very rarely) when a strong collision (edge <- body1 <- body2) happens directly near the edgeLoopFromRect physics body, sometimes colliding-object (body1) jumps out. I am totally confused how to debug this kind of behaviour.
EDIT: I have recorded a video of what exactly happens:
Physics engine collapses
For the demo I have made impulse strength (the biggest blue ball) on purpose 10-times stronger, so the effect can be seen sooner. Look what happens after 10-15 seconds. Physics totally collapses. This can be seen by background totally going off and balls fly into the unknown.
Note: everything I do in this demo is applying impulse on the blue ball.
You need to enable usesPreciseCollisionDetection. This will force SpriteKit to calculate the physics positions of the entire movement, which will now prevent it from popping out. Code for this would look like this in Objective-C:
self.body1.physicsBody.usesPreciseCollisionDetection = YES;
And in Swift:
body1.physicsBody?.usesPreciseCollisionDetection = true
This will have a performance impact, but will prevent your glitch from happening. You will probably have to do this for all of the circular physics bodies that you have moving around.
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.