I am writing an iphone game using cocos2d and box2d engines.
I have a ball which can be jumped by tapping the screen. The jump is applied by using ApplyImpulse method on the ball's body.
Thing is I do not want the ball to jump more than once. (i.e. If the ball is in mid-air I do not want it to be jumped again when tapping the screen.)
Is there a way to know when an object is in mid-air ?
Is there a common solution to this problem ?
Thanks
You can raycast from the center of the ball, downwards. If it collides with anything at a distance greater than the ball's radius, that means it is in the air.
To raycast, check chapter 10 in the manual here:
http://box2d.org/manual.pdf
It's in c++ but you should find similar examples in objective-c.
Hope it helps.
Related
i have made an app where you need to shoot on an enemy but sometimes the bullet goes through the enemy. swift sprite kit game when I shoot on a enemy sometimes the bullet goes trough the enemy, how can I fix this?
so i added usesPreciseCollisionDetection = true.
but the bullet sometimes still goes trough the enemy. so my question was did i do something wrong or is usesPreciseCollisionDetection not working?
thank you for reading my question I hope someone can help me.
You are using moveTo to move your bullets, Physics Engine does not work with moveTo the way you want it to, usesPreciseCollisionDetection will not do anything
As far as your Physics World is concerned, your bullet is stationary. You are just playing God and performing some kind of molecular transportation to move items.
You need to use functions like applyImpulse or even just give the physicsBody a velocity if you want this to work correctly
I had similar problem that is collision was sometimes not detected even when usesPreciseCollisionDetection was set to true and both SKPhysicsBody were rectangles. In my case usesPreciseCollisionDetection for some reason started working much better when I changed one of the SKPhysicsBody to circle instead of rectangle. Try changing your bullet physics body to circle, it seems that collision detection algorithm with circles is more precise so that might help you.
I've started learning sprite kit and I think I've got the basics but now I'm struggling with something.
I want to create a game that has a 'Streets of rage' type feel to it whereby the user can move up and down, but isn't jumping, they're still on a 2D plane. But I also want them to be effected by gravity e.g stairs etc. like the following picture.
Am I right in assuming that I should have my background image with colliders around the blue and brown edges, and then create a physicsbody collider located at the feet of my player/players so that it looks like they can move against the background, but when their feet reach the top it would stop?
Could I then place other obstacles like rocks etc on that path that they would be able to collide into, but that could also sit over the path and the sky? How would I handle the fact that these could be constantly colliding depending on the position?
I appreciate there isn't any code here, but I'm trying to understand the concept around this before I jump in coding a solution.
Thanks
I would use a categoryBitMask to separate the different planes of objects.
And I would play with collisionBitMask/contactTestBitMask depending from the plane the player is in, in addition to the z-order.
Thus you can have a rock that collides your player if they are both in the same line else the player would walk behind/front.
I'm making a fps game and I want my character's arms to rotate up and down depending where the cursor/camera is pointing at. The character already rotates when I turn left or right. Hopefully someone can answer my question. I'm new to Unity and I'm still learning how to code in C#.
For top and bottom rotation, create an animation for top aim, eye level aim and feet aim. send the value of your rotation to animator controller and animate according to it.
Hello everyone I an very new to cocos2d, so I apologize if this is a simple question. I would like to create to sprites that collide when they hit each other.
For instance, one sprite, spriteA, is in a fixed position on the screen. And another sprite, spriteB, is moving around the screen. SpriteB will collide with spriteA. If that doesn't make sense or you don't understand it, tell me and I will elaborate further. Any help is appreciated. Thank YOU!
Try using Chipmunk or Box2d physics systems. These are included with Cocos2d and work by having a physics simulation that updates with every time the graphics change on screen.
The physics simulation will tell you if two objects are overlapping, and will provide physical attributes like weight, slipperiness (friction), speed and direction, which creates reactions like bouncing, sliding, realistic loss of speed and changes of direction on impact.
If you are new to physics simulation, here's a 30 second run down:
Create "bodies" in the physics simulation that represent each graphical sprite
Bodies are usually defined more simply than their graphical counterparts, like a circle, square or simple polygon shape
In order to update the graphics on the screen accurately, first you establish a pixels to meters ratio. Meters are notional (i.e. made up) measurement that is used in the physics sim
Each time the physics simulation "ticks", you update the graphics on screen accordingly
So if a body in the physics sim moves 1 meter, you might transform the pixel sprite 32 pixels
Here's a good tute on collision detection using Box2d.
http://www.raywenderlich.com/606/how-to-use-box2d-for-just-collision-detection-with-cocos2d-iphone
enjoy
Its actually very simple:
Just schedule a timer: [self schedule:#selector(checkForCollision:)];
Specify the method: - (void)checkForCollision:(ccTime)dt {}
In the curly braces, make CGRects for each sprite using CGRectMake.
Then in the same method, just call: if (CGRectIntersectsRect) {}
That easy!
Well technically speaking when the 2 sprites interact, or share at least one common point, then they are colliding. I'm a little confused by your question. Are you asking for direction on how to make the sprite move on screen, or are you asking how to handle the actual collision(such as calling a method if they collide)?
I have a simple project built with Cocos2D and Chipmunk. So far it's just a Ball (body, shape & sprite) bouncing on the Ground (a static line segment at the bottom of the screen).
I implemented the ccTouchesBegan/Moved/Ended methods to drag the ball around.
I've tried both:
cpBodySlew(ballBody, touchPoint, 1.0/60.0f);
and
ballBody->p = cgPointMake(touchPoint.x,touchPoint.y);
and while the Ball does follow my dragging, it's still being affected by gravity and it tries to go down (which causes velocity problems and others).
Does anyone know of the preferred way to Drag an active Body while the physics simulation is going on?
Do I need somehow to stop the simulation and turn it back on afterwards?
Thanks!
Temporarily remove the body from the space.
If you want the object to have inertia when you release it, that's a different story. The cleanest way is to attach a fairly stiff spring between the ball and a temporary sensor body that moves under the control of your finger. When you let go with your finger, the ball will retain whatever kinematics it had while you were dragging it. Be sure not to remove the ball from the space in this case.
You aren't updating the velocity of the object when you aren't using cpBodySlew(). That is why it falls straight down.
A better way to do it is to use a force clamped pivot joint like the official demos do to implement mouse control. http://code.google.com/p/chipmunk-physics/source/browse/trunk/Demo/ChipmunkDemo.c#296