I've got a problem with my current project.
What I'd like to do is make a b2Body move up and down repeatedly. I already know how to do this with a CCSprite:
[paddle runAction:[CCRepeatForever actionWithAction:
[CCSequence actions:
[CCMoveTo actionWithDuration:1.0 position:ccp([paddle position].x,[paddle position].y+40)],
[CCMoveTo actionWithDuration:1.0 position:ccp([paddle position].x,[paddle position].y)],
nil
]]];
Can anybody help me do the same thing with a b2Body?
Thanks in advance!
You will have to implement the sequence yourself, which involves:
keeping track of the current target position
from the current position of the body, detect whether it has reached the target
if it has, change the target position
apply force, impulse or set velocity as necessary to move the body
You might be able to extend CCMoveTo to make your own class to do this... I would look into that first.
i've got it dude,
in almost explanation, every CCsprite move depend on b2body movement -that movement is placed at 'tick' method-.
in my case, i reverse that way, i move b2body according to CCsprite movement on tick method, so i give these code on tick method:
for(b2Body *b = _world->GetBodyList(); b; b=b->GetNext()) {
if (b->GetUserData() != NULL) {
CCSprite *sprite = (CCSprite *)b->GetUserData();
if (sprite.tag == 4 || sprite.tag == 5) {
b2Vec2 b2Position = b2Vec2(sprite.position.x/PTM_RATIO,
sprite.position.y/PTM_RATIO);
float32 b2Angle = -1 * CC_DEGREES_TO_RADIANS(sprite.rotation);
b->SetTransform(b2Position, b2Angle);
}
}
}
Related
ok so i've been messing around with chipmunk a bit, and i can get two sprites to bounce off of each other, but when i try to use the following method, it never fires,
-(BOOL)ccPhysicsCollisionBegin:(CCPhysicsCollisionPair *)pair tower:(CCNode *)nodeA BG:
(CCNode *)nodeB
{
NSLog(#"HELLO");
return YES;
}
Heres where I create the physics node:
_physics = [CCPhysicsNode node];
_physics.debugDraw = YES;
[self addChild:_physics z:1];
_physics.collisionDelegate = self;
I use this code to create the first sprite:
background = [CCSprite spriteWithImageNamed:gameLevelImage];
[background setPosition:ccp(winSize.width/2,winSize.height/2)];
background.physicsBody.collisionType = #"BG";
background.physicsBody = [CCPhysicsBody bodyWithCircleOfRadius:50 andCenter:self.position];
and this for the other :
tower = [[TowerType alloc] initWithTheGame:self location:ccp(winSize.width/2, winSize.height/2)];
[towers addObject:tower];
[self MenuItemsVisible];
tower.physicsBody = [CCPhysicsBody bodyWithCircleOfRadius:50 andCenter:tower.position];
tower.physicsBody.collisionType = #"tower";
I also have the protocol in the h file.
if anyone knows whats happening help would be greatly appreciated. (:
First of all, are both bodies under the same CCPhysicsNode?
Second, ccPhysicsCollisionBegin is just called when the collision BEGIN, so as both of your bodies are one over the other and they aparenttly will move together due to gravity the collision will never begin, because they started colliding. The cycle for collision evaluation is:
ccPhysicsCollisionBegin: called once both bodies start colliding
ccPhysicsCollisionPreSolve: called every frame update, before physics calculations
ccPhysicsCollisionPostSolve : called every frame, after physics calculations
ccPhysicsCollisionSeparates: called once they separate
Make sure your sprites are allocated properly before you try to set the collisionType. That was the issue for me in my similar case.
In cocos2d, you can ease in CCSprites and move them around in all kinds of ways. Most importantly - they can have easing in/out. For most games this is desirable for smooth movement etc.
id action = [CCMoveTo actionWithDuration:dur position:pos];
move = [CCEaseInOut actionWithAction:action rate:2];
[self runAction: move];
When moving a box2d body, the sprite attached to it is updated after the box2d step(). Moving the sprite and then updating the body is not an option here, as it entirely defeats the purpose of the physics framework.
So the other option, which I have successfully implemented, is to calculate the displacement, velocity and acceleration of a sprite by treating it as a mechanics entity in its own right. Each time I call my update() on the sprite so the character can decide where to move etc, my superclass also stores the previous position and velocity. These are stored as box2d compliant values by dividing by the PTM_RATIO.
In the subclass of CCSprite, called FMSprite:
-(CGPoint) displacement {
return ccpSub(self.position, lastPos);
}
-(b2Vec2) getSpriteVelocity:(ccTime)dt {
return b2Vec2(self.displacement.x / dt / PTM_RATIO,
self.displacement.y / dt / PTM_RATIO);
}
-(b2Vec2) getSpriteAccel:(ccTime)dt {
b2Vec2 currVel = [self getSpriteVelocity:dt];
if (dt == 0) {
return b2Vec2(0,0);
} else {
float accelX = (currVel.x - lastVel.x)/dt;
float accelY = (currVel.y - lastVel.y)/dt;
return b2Vec2(accelX, accelY);
}
}
// This is called each update()
-(void) updateLast:(ccTime)dt {
// MUST store lastVel before lastPos is updated since it uses displacement
lastVel = [self getSpriteVelocity:dt];
lastPos = ccp(self.X, self.Y);
}
// Leave this method untouched in subclasses
-(void) update:(ccTime)dt {
[self updateObject:dt];
// Store previous update values
[self updateLast:dt];
}
// Override this method in subclasses for custom functionality
-(void) updateObject:(ccTime)dt {
}
I have then subclassed "FMSprite" into "FMObject", which stores a b2Body etc.
In order to move the body, I must first move a sprite and track its acceleration, through which I can find the required force (using the mass) needed to follow the sprite's motion. Since I can't move the object's sprite (which is synchronized to the body), I make another sprite called a "beacon", add it as a child to the object, and move it around. All we need to do then is to have a function to synchronize the position of the box2d body with this beacon sprite using the forces I mentioned before.
-(void) followBeaconWithDelta:(ccTime)dt {
float forceX = [beacon getSpriteAccel:dt].x * self.mass;
float forceY = [beacon getSpriteAccel:dt].y * self.mass;
[self addForce:b2Vec2(forceX, forceY)];
}
The result is brilliant, a smooth easing motion of the b2body moving where ever you want it to, without playing around with any of its own forces, but rather copying that of a CCSprite and replicating its motion. Since it's all forces, it won't cause jittering and distortions when colliding with other b2Body objects. If anyone has any other methods to do this, please post an answer. Thanks!
What I do is different from yours, but can also Moving Box2d Bodies Like CCSprite Objects and even use the CCAction.
The most important thing is to create an object that contain ccSprite and b2body.
#interface RigidBody : CCNode {
b2Body *m_Body;
CCSprite *m_Sprite;
}
And then, rewrite the setPosition method.
-(void)setPosition:(CGPoint)position
{
CGPoint currentPosition = position_;
b2Transform transform = self.body->GetTransform();
b2Vec2 p = transform.p;
float32 angle = self.body->GetAngle();
p += [CCMethod toMeter:ccpSub(position, currentPosition)];
self.body->SetTransform(p, angle);
position_ = position;
}
The setPosition method calculate how much the position change,and set it to the b2body.
I hope I have understanding your question and the answer is helpful for you...
I've got to sprites, essentially a nucleus (parent) and an electron (child). I'm trying to find a way to have the electron orbit the nucleus. I've found a few posts here and there on moving anchor points, but that is apparently related to the texture of the sprite, not the sprite itself.
This is my current init method for my parent sprite:
self = [super init];
if (self) {
CCSprite *orbitAnchor = [CCSprite new];
[self addChild:orbitAnchor];
orbitAnchor.position = ccp(32,32);
CCSprite *orbiter = [CCSprite spriteWithFile:#"line.png" rect:CGRectMake(0, 0, 8, 8)];
[orbitAnchor addChild:orbiter];
orbiter.position = ccp(40,40);
CCAction *orbitAction = [CCRepeatForever actionWithAction:[CCRotateTo actionWithDuration:1 angle:720]];
[orbitAnchor runAction:orbitAction];
[self initAnimations];
}
return self;
Those numbers are all totally arbitrary though - I just stuck them in there and got what looked best. I'm sure there's a more programatic way to do what I want.
Basically, I'm looking for a way to set the child's axis point at the center of the parent, and then have it rotate around that point. It seems like a relatively simple thing to do using CCRotate and such, but I think I'm missing what to search for in order to move the anchor point of the child. Any suggestions/other posts?
Thanks
You have [CCSprite new] which is an unusual use, probably not supported. Unless the orbit anchor node should display a texture, you can just use a CCNode as anchor.
Technically you're doing everything correct from what I can see. You might want to try without the rotate actions and instead change the direction manually in a scheduled update method.
CCNode *orbitAnchor = [CCNode node];
[self addChild:orbitAnchor z:0 tag:1];
orbitAnchor.position = ccp(32,32);
CCSprite *orbiter = [CCSprite spriteWithFile:#"line.png" rect:CGRectMake(0, 0, 8, 8)];
[orbitAnchor addChild:orbiter z:0 tag:2];
orbiter.position = ccp(40,40);
[self scheduleUpdate];
Update method:
-(void) update:(ccTime)delta
{
CCNode* orbitAnchor = [self getChildByTag:1];
orbitAnchor.direction += 5;
}
From the image filename it looks like you're trying to draw a line from the orbitAnchor to the orbiter. You can do that with ccDrawLine:
-(void) draw
{
CCNode* orbitAnchor = [self getChildByTag:1];
CCNode* orbiter = [self getChildByTag:2];
ccDrawLine(orbitAnchor.position, orbiter.position);
}
Anchor points. Automatically, objects are placed based on the center of an object right? with anchor points you can move that around, so if you rotate the object it will rotate around the anchorpoint. http://www.qcmat.com/understanding-anchorpoint-in-cocos2d/
since i havnt got an answer in my previos post, and no one solve that problem , i am asking this again. there is no 1 explanation regarding this.
i need to detect a sprite touch, a SPECIFIC one. in cocos2d+box2d.
lets say i have sprite CCSprite *ran that has a body, BUT , i have many of it .
if i detect a touch with the ccTouchesBegan , and use the if(CGRectContainsPoint(particularSpriteRect, currentPosition))
i will detect the touch in ran but i dont know who ran is this from all, and i need to destroy than specific ran , which i cant know who it was .
i find the best way to do that, as i do with contact listener that gives me the specific sprite user data :
CCSprite *actora = (CCSprite*)bodyA->GetUserData();
CCSprite *actorb = (CCSprite*)bodyB->GetUserData();
and then i know that actora is what needs to be destroy cause i have his user data.
[self removeChild:actora cleanup:YES];
so , again , i need to detect a sprite touch and KNOW who it was,cause i have many ran's.
i guess its something needs to involve the userData .
any direction please ?
thanks alot.
ok, i have got it :
this is what i do, to destroy the specific body, different from what was said here :
put the next code in the touch method :
CGPoint currentPosition = [touch locationInView: [touch view]];
currentPosition = [[CCDirector sharedDirector] convertToGL: currentPosition];
b2Vec2 locationWorld = b2Vec2(currentPosition.x/PTM_RATIO, currentPosition.y/PTM_RATIO);
for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())
{
b2Fixture *bf1 = b->GetFixtureList();
if (bf1->TestPoint(locationWorld))
{
CCSprite *tempSprite = (CCSprite *) b->GetUserData();
if (tempSprite .tag==2 || tempSprite .tag==3)
{
[self removeChild:tempSprite cleanup:YES];
world->DestroyBody(b);
}
}
}
here if you touch the right sprite(tagged) , it get destroyed .
I just have a simple sprite - how can I get it to rotate?
A good answer would show how to rotate both a dynamic sprite and a static_mass sprite
If the sprite is dynamic / non-static, just do like so:
cpBodySetAngVel(ObjSmSprite.shape->body,0.25);
For a static body, you can do something like this:
[ObjSmStaticSprite.shape runAction:[CCRepeatForever actionWithAction:
[CCSequence actions:
[CCRotateTo actionWithDuration:2 angle:180],
[CCRotateTo actionWithDuration:2 angle:360],
nil]
]];
smgr.rehashStaticEveryStep = YES; //Setting this would make the smgr recalculate all static shapes positions every step
To Summarize, here is a spinning static sprite, following be spinning dynamic sprite.
// Add Backboard
cpShape *shapeRect = [smgr addRectAt:cpvWinCenter mass:STATIC_MASS width:200 height:10 rotation:0.0f ];// We're upgrading this
cpCCSprite * cccrsRect = [cpCCSprite spriteWithShape:shapeRect file:#"rect_200x10.png"];
[self addChild:cccrsRect];
// Make static object update moves in chipmunk
// Since Backboard is static, and since we're going to move it, it needs to know about spacemanager so its position gets updated inside chipmunk.
// Setting this would make the smgr recalculate all static shapes positions every step
// cccrsRect.integrationDt = smgr.constantDt;
// cccrsRect.spaceManager = smgr;
// Alternative method: smgr.rehashStaticEveryStep = YES;
smgr.rehashStaticEveryStep = YES;
// Spin the backboard
[cccrsRect runAction:[CCRepeatForever actionWithAction:
[CCSequence actions:
[CCRotateTo actionWithDuration:2 angle:180],
[CCRotateTo actionWithDuration:2 angle:360],
nil]
]];
// Add the hoop
cpShape *shapeHoop = [smgr addCircleAt:ccp(winSize.width/2.0f,winSize.height/2.0f - 55.0f) mass:1.0 radius: 50 ];
cpCCSprite * cccrsHoop = [cpCCSprite spriteWithShape:shapeHoop file:#"hoop_100x100.png"];
[self addChild:cccrsHoop];
cpBodySetAngVel(cccrsHoop.shape->body,0.25);
Disclaimer: I'm trying to answer my own question, and this answer might be missing important subtleties - it just represents what I know, so far.
If using cocos2d
use this code in tick to update positon all time _number1.position is the position you would update to, so when _number1 moves _logo2 will rotate to face it
_logo2.rotation = CC_RADIANS_TO_DEGREES(-ccpToAngle(ccpSub(_number1.position, _logo2.position)));
update _logo1 rotation by touch put this code in touch event handler
_logo2.rotation = CC_RADIANS_TO_DEGREES(-ccpToAngle(ccpSub(location, _logo2.position)));
use this as an action
[_logo2 runAction:[CCRotateTo actionWithDuration:0.0 angle:CC_RADIANS_TO_DEGREES(-ccpToAngle(ccpSub(location, _logo2.position)))]];
hope this helps someone took me ages to work it out