Here is the code for setting the characters physics body.
character.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:character.size];
It works fine, I mean it stays where I want it to but as you can see it displays the character's physics body in the bottom left of the screenshot (which is the grey box).
Is this a bug or can this be fixed?
I had a similar problem which may or may not solve yours.
It looks like you are using some sort of viewport system. Perhaps with a node called world and one called camera? If this is the case then you must be moving your world node every frame in order to center the content correctly? When drawing physics, you need to move the world node at -didEvaluateActions instead of -didSimulatePhysics
Related
Am I the only one whose having issues with the new bodyWithTexture function of SKPhysicsBody?
I'm new to iOS development and maybe it's me, but I'm trying to create a game where I need to detect if a ball is inside a path.
I'm loading both from images dynamically (as the level proceeds the paths are more and more complex), and I'm setting a physics body to both the ball (bodyWithCircle) and from the dynamic path which is a PNG file of a path and all the rest is transparent background. I'm using the new bodyWithTexture function (yes I know it's supported only under iOS 8), and after assigning bit masks I've defined a contact between the ball and path and am informed with begin/end contact.
SKSpriteNode *lvlPath = [SKSpriteNode spriteNodeWithImageNamed:currentLevel.imagePath];
lvlPath.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
lvlPath.physicsBody = [SKPhysicsBody bodyWithTexture:lvlPath.texture size:lvlPath.frame.size];
now for simple paths like straight line, it works great. once it comes to complicated paths - the mechanism is going crazy, at least in my simluator (running iOS 8).
i've created another simple app just to check this issue, and saw that it's going crazy when the path is a complex shape. when the ball enters the path in one direction it seems to be working (begin/end contact), but going the reverse direction suddenly acts weird when still inside the path it reports to have ended contact, and then like randomly flips begin/end contact.
help... since the levels are loaded dynamically, this is a really cool feature for me, saving me the definitions of all levels as CGPathRef and creating a polygon for each level (and perhaps device).
thanks all,
Eyal
edit
example screenshot:
https://www.dropbox.com/s/e8v9g1kajtvakfq/screenshot%20bodywithtexture.jpg?dl=0
in this example the ball with the arrow is inited using bodyWithCircle, and the C shaped object is inited using bodyWithTexture. I'm debug printing "didBeginContact" and "didEndContact" and it freaks out in the top line there, you can see it's with "didEndContact" while the two object are definitely at contact. If I jiggle it (I'm moving it with the cursor) it suddenly flips to "didBeginContact".
With Simpler objects (like horizontal/vertical lines with round corners) it works perfectly.
I have a ship that everything is centered around and everything moves relative to it. It is a first person shooter. Right now when I fire, and the ship speeds up, it catches up to the bullets. I would like the physics world to move relative to the ship's speed so that the bullet is essentially unaffected by ship speed.
The physics engine is doing the right thing, but not the right thing for my game.
I have other elements that move relative to the ship as it moves, which move correctly now, so don't want make ship stationary and move everything else in world around it. I don't see a direct way to do this maybe there is an indirect way? Perhaps I can manually take over the positioning of the bullets. I would like to use the other parts of the physics engine for doing collisions etc so don't want to completely manually do it, but will if that is the only option.
Anyone else have any suggestions?
It sounds like your bullets are receiving air friction. This is controlled by the physics bodies "damping" property. A value of 1.0 will make it static without movement. A value of 0 will allow it to move continuously without ever stoping. The default value is 0.1 as per the Apple documents. Assign your node like so to remove the damping(air friction)...
yourNode.physicsBody.damping = 0
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.
Recently I have a new project that uses Box2D as physics engine. And I am having some trouble with the body's position.
I want to draw images on the sprite, so I just use body.GetPosition as image's position. But I found that body.GetPosition returns the same value as body.GetWorldCenter, and I just wondering that I did something wrong.
I use box2d flash 2.1a in my project. And I currently subtract this position with half-width and half-height to walk around. Also, can you tell me if there is some way to solve my problem or draw the image in the correct positon in Box2D.
Thank you.
update
so sorry to post before read manual.
after RTM I got that body has two points,first is origin point and the second is center of mass ,so a regular shape's world center is always the same as it's origin point. sorry to post is.
Have you set the image in the userdata for the body? Your getting the body's position but you need to have a function that runs each world tick that can set the images position to the new location. Box2d is just numbers defining a simulation. Those numbers are constantly updating so the image needs to have position set each time there is a game tick. Hope this helps
currently I'm developing a simple game which uses physics engine (Farseer for XNA).
I would like to ask how can I make the character so that he can walking on the ground, jumping on platform without rotating itself.
Because I need to update the body position and rotation, because it is a physics object so it will response like the usual which will rotate itself.
Anyone know how can I fix it?
For Farseer 2.1 you can set:
body.MomentOfInertia = float.PositiveInfinity;
Farseer 3.0 appears to have a flag for fixed rotation, which appears to do the same thing internally:
body.FixedRotation = true;
Although I also set rotation to zero after the physics update, just to be sure:
body.Rotation = 0;
Don't be afraid to go in, after your physics update runs, and change any physics values you "don't like". Most games fake and fudge things quite a lot.