using cocos2d and box2d i am taking a body and put a sprite that follow him, now i would like to see not only the sprite but the whole world bodies shapes(boxs,and circles) to understand better my world physics.
the sprite follow a body with :
world->Step(dt,10,10);
for(b2Body *b=world->GetBodyList(); b; b=b->GetNext()) // b is the list of all bodys in the world and we running on them
{
if(b->GetUserData() !=NULL )
{
CCSprite *sprite=(CCSprite *) b->GetUserData();//every b of the world will be update his position
sprite.position=ccp( b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO ) ;
sprite.rotation=-1*CC_RADIANS_TO_DEGREES(b->GetAngle());
}
}
how would i do that? is it require a big code ?
thanks a lot.
Use b2DebugDraw. Here is the code how do it:
http://www.ccsprite.com/box2d/debugdraw-box2d-cocos2d.html
That will automatically draw your b2World.
Related
I have a few layers, which holds CCSprites .
I have a main CCScene that is adding these layers at the start.
I have to check collision between sprites from different layers .
I know how to check a simple collision with CGRectContains , my problem is , that i need some kind of a class that holds all the sprites positions from all layers ,and to check each tick for collision.
Question: what is the right way to create such a class,that save/check sprites from all layers on the scene ?
THanks .
If you don't care about empty space, then you can just set self.contentSize for every layer. You can do it like this:
CGRect rect = CGRectNull;
for (CCNode *node in self.children) {
rect = CGRectUnion(rect, node.boundingBox);
}
self.contentSize = rect.size;
But if you care about empty space, then you need to use something like this:
// put it somewhere outside class implementation
static inline BOOL CCLayerIntersectsCCLayer(CCLayer l1, CCLayer l2) {
for (CCNode *n1 in l1.children) {
for (CCNode *n2 in l2.children) {
CGRect r1 = n1.boundingBox;
CGRect r2 = n2.boundingBox;
r1.origin = [l1.parent convertToNodeSpace:r1.origin];
r2.origin = [l2.parent convertToNodeSpace:r2.origin];
if (CGRectIntersectsCGRect(r1, r2)) {
return YES;
}
}
}
return NO;
}
But you must understand, that all sprites (even circles) are actually rectangles. So if you need very precise collision detection, then you should use box2d in your project. If you are interesting in this, here are some links to read:
Box2d
Intro to Box2D with Cocos2D 2.X Tutorial: Bouncing Balls
Box2D Tutorial for iOS: How To Use Box2D For Just Collision Detection with Cocos2D iPhone
In my scene class I've overridden the update function and I call scheduleUpdate() in the onEnter() method as suggested here. So in the update function I call the update of my layer class which should update my sprites:
void View::update(float dt)
{
world->Step(dt, 10, 10);
for(b2Body *b = world->GetBodyList(); b; b=b->GetNext())
{
if(b->GetUserData() != NULL && b->GetType() != b2_kinematicBody))
{
cocos2d::CCSprite *data = (cocos2d::CCSprite*)b->GetUserData();
data->setPosition(ccp(b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO));
data->setRotation(-1 * CC_RADIANS_TO_DEGREES(b->GetAngle()));
}
}
}
At the moment, the only movement is falling down because of gravity. However, the character moves so fast. It almost instantaneously hits the floor. Is there a way to slow this down?
When I used this tutorial for objective c, the ball was falling down much slower.
Did you correctly set the mass of your character? Try to reduce it. Also I recommend you to use a small wrapper which makes life with box2d and cocos2d-x much easier.
Found the problem. I set the position of my sprite to the center of my screen, but I set the position of the body to the bottom. So in the first frame the sprite immediately appeared on the bottom side.
So if anyone has the same problem: check the position of your body. Not just the sprite's position.
I have a question that is killing me...
I'm using LevelHelper to make a level in Box2d. So I have a triangular sprite attached to a triangular body.
Now the problem is that I want to rotate that body to a position, and rotate the attached sprite too.
Here you have some code:
//Detecting my actor and my sprite
if (b->GetType() == b2_dynamicBody && myActor == [loader spriteWithUniqueName:#"radar."]){
radar = b;
radarSprite = myActor;
}
Just wanted to try with 20 degrees, but it's not rotating.
//trying to rotate inside TICK: Method
float32 b2Angle = -1 * CC_DEGREES_TO_RADIANS(20);
radar->SetTransform(radar->GetPosition(), b2Angle);
radarSprite.position = ccp(radar->GetPosition().x,radar->GetPosition().y);
Any tips?
Thank you very much in advance!!
you have an error, you rotate only the physic body, levelhelper have a method in the LHSprite called tranformRotation, so you need do this:
this method rotate the body and the sprite (if the body attach to sprite):
//radarSprite is a LHSprite
float32 b2Angle = -1 * CC_DEGREES_TO_RADIANS(20);
[radarSprite transformRotation:b2Angle];
[radarSprite transformPosition:ccp(radar->GetPosition().x,radar->GetPosition().y)];
if you have the body separate from sprite you can do this:
//radarSprite is a LHSprite
float32 b2Angle = -1 * CC_DEGREES_TO_RADIANS(20);
radar->SetTransform(radar->GetPosition(), b2Angle);
[radarSprite transformRotation:b2Angle];
[radarSprite transformPosition:ccp(radar->GetPosition().x,radar->GetPosition().y)];
EDIT:
the method spriteWithUniqueName return a LHSprite, but if you use CCSprite you can do this:
//radarSprite is a CCSprite
float32 b2Angle = -1 * CC_DEGREES_TO_RADIANS(20);
radar->SetTransform(radar->GetPosition(), b2Angle);
[radarSprite setRotation:b2Angle];
[radarSprite setPosition:ccp(radar->GetPosition().x,radar->GetPosition().y)];
I want to build a platform game with cocos2d/Box2D. I use CCFollow to follow the player sprite but CCFollow constantly puts it in the center of the screen. I want CCFollow to follow more naturally, like a human turning a camcorder with an acceptable lag, a small overshoot ...etc.
Here is a method of mine that didn't work: I attached (via a distance joint) a small physics body to the player that doesn't collide with anything, represented by a transparent sprite. I CCFollow'ed the transparent sprite. I was hoping this ghost body would act like a balloon attached to the player, hence a smooth shift in view. The problem is distance joint breaks with too heavy - too light objects. The balloon moves around randomly, and of course, it pulls the player back a little no matter how light it is.
What is a better way of following a moving sprite smoothly?
Try add this to CCActions in cocos2d libs.
-(void) step:(ccTime) dt
{
#define CLAMP(x,y,z) MIN(MAX(x,y),z)
CGPoint pos;
if(boundarySet)
{
// whole map fits inside a single screen, no need to modify the position - unless map boundaries are increased
if(boundaryFullyCovered) return;
CGPoint tempPos = ccpSub(halfScreenSize, followedNode_.position);
pos = ccp(CLAMP(tempPos.x,leftBoundary,rightBoundary), CLAMP(tempPos.y,bottomBoundary,topBoundary));
}
else {
// pos = ccpSub( halfScreenSize, followedNode_.position );
CCNode *n = (CCNode*)target_;
float s = n.scale;
pos = ccpSub( halfScreenSize, followedNode_.position );
pos.x *= s;
pos.y *= s;
}
CGPoint moveVect;
CGPoint oldPos = [target_ position];
double dist = ccpDistance(pos, oldPos);
if (dist > 1){
moveVect = ccpMult(ccpSub(pos,oldPos),0.05); //0.05 is the smooth constant.
oldPos = ccpAdd(oldPos, moveVect);
[target_ setPosition:oldPos];
}
#undef CLAMP
}
i get this from cocos2d forums.
Perhaps this http://www.cocos2d-iphone.org/wiki/doku.php/prog_guide:actions_ease can help you get an "acceleration" effect with CCFollow.
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...