Currently, in cocos2d, I have a an app that does the following:
Initiate with a Blank Screen.
When I tap the screen, I get a circle to pop-up. As I hold the circle, the circle will continue to grow at a constant rate. However, despite the fact that the sprite is growing, the box2d physical body isn't, which means that the sprite will not collide with other bodies. I been trying to figure out a way to change the radius that scales with the sprite but no such question exist here for cocos2d. I have noticed other box2d for things other than cocos2d but I am having a hard time translating them over.
//smile.position = ccp(touchLocation.x, touchLocation.y);
smile.scale = .05;
[self addChild:smile];
// b2BodyDef smileBodyDef;
smileBodyDef.type = b2_dynamicBody;
smileBodyDef.position.Set(touchLocation.x/PTM_RATIO, touchLocation.y/PTM_RATIO);
smileBodyDef.userData = smile;
smileBody = world->CreateBody(&smileBodyDef);
//Radius
b2CircleShape smileCircleShape;
int radius = 80;
//Fixture
smileFixtureDef.shape = &smileCircleShape;
smileFixtureDef.density = 0.00f;
smileFixtureDef.friction = .2f;
smileBody->CreateFixture(&smileFixtureDef);
if (CGRectContainsPoint(smileRect, touchLocation)) {
growForever = [CCRepeatForever actionWithAction: [CCScaleBy actionWithDuration: .5 scale: 1.2]];
[growForever setTag:1];
[smile runAction:growForever];
Each time you want to change your radius, grab the shape object associated with the b2Fixture that you created for your body, and then set the new value accordingly:
fixture->GetShape()->m_radius = new_radius/PTM_RATIO;
Related
I am working with tile map and box2d with cocos2D in the game for iOS, i want to move the tile with respect to physics bodies, i.e. to combine one or more tiles in a body and on contact if body is moving then tile sprites should also move. Please suggest something to do so.
You could use a CCPhysicsSprite for this.
The following code is from the default Box2D project in Cocos2d v2.
-(void) addNewSpriteAtPosition:(CGPoint)p
{
CCLOG(#"Add sprite %0.2f x %02.f",p.x,p.y);
// Define the dynamic body.
//Set up a 1m squared box in the physics world
b2BodyDef bodyDef;
bodyDef.type = b2_dynamicBody;
bodyDef.position.Set(p.x/PTM_RATIO, p.y/PTM_RATIO);
b2Body *body = world->CreateBody(&bodyDef);
// Define another box shape for our dynamic body.
b2PolygonShape dynamicBox;
dynamicBox.SetAsBox(.5f, .5f);//These are mid points for our 1m box
// Define the dynamic body fixture.
b2FixtureDef fixtureDef;
fixtureDef.shape = &dynamicBox;
fixtureDef.density = 1.0f;
fixtureDef.friction = 0.3f;
body->CreateFixture(&fixtureDef);
CCNode *parent = [self getChildByTag:kTagParentNode];
//We have a 64x64 sprite sheet with 4 different 32x32 images. The following code is
//just randomly picking one of the images
int idx = (CCRANDOM_0_1() > .5 ? 0:1);
int idy = (CCRANDOM_0_1() > .5 ? 0:1);
CCPhysicsSprite *sprite = [CCPhysicsSprite spriteWithTexture:spriteTexture_ rect:CGRectMake(32 * idx,32 * idy,32,32)];
[parent addChild:sprite];
[sprite setPTMRatio:PTM_RATIO];
[sprite setB2Body:body];
[sprite setPosition: ccp( p.x, p.y)];
}
NOTE The position of the sprite has been set after the body has been created. If you do it the other way around, you may get an exception. See here.
In my game I have a block sprite. With this sprite I've made a blockbody so that my character can't walk through it.
cocos2d::CCSprite* block = cocos2d::CCSprite::create("Block.png");
block->setPosition(ccp(5,20));
this->addChild(block);
b2BodyDef blockbodydef;
blockbodydef.type = b2_kinematicBody;
blockbodydef.position.Set(5/PTM_RATIO,20/PTM_RATIO);
blockbodydef.userData = block;
b2Body *blockbody = world->CreateBody(&blockbodydef);
b2PolygonShape blockPoly;
blockPoly.SetAsBox(37.5/PTM_RATIO , 37.5 / PTM_RATIO);
b2FixtureDef blockshapedef;
blockshapedef.shape = &blockPoly;
blockshapedef.density = 2.0f;
blockshapedef.friction = 0.2f;
blockshapedef.restitution = 0.8f;
blockbody->CreateFixture(&blockshapedef);
However, I want to have multiple of these blocks. Is there a way to like change the position of the bodydef and sprite without the original sprite disappearing or do I have to create a different sprite for each block?
You have to create another sprite for another block. Textures are cached inside cocos2dx, so it will be loaded from file only once.
I'm trying to make a tank in cocos2d-x with box2d. Everything works fine but when i draw the tank, the barrel is in the middle as you can see in the picture.
To draw the tank i set the position to the center of the screen, after the tank body is drawn i want to draw the barrel and i give it the center of the screen + the same offset of the joint (the joint is on the right position).
Both anchor points, the tank and barrel are on (0.5, 0.5) and because i use the same offset as the joint i expected the barrel was drawn at the right place but it's not.
My code:
// Create sprite and add it to the layer
CCSprite *tank = CCSprite::create();
//tank->initWithFile("Tanks/001/tank.png");
tank->setPosition(pos);
tank->setTag(1);
this->addChild(tank);
// Create ball body
b2BodyDef tankBodyDef;
tankBodyDef.type = b2_dynamicBody;
tankBodyDef.position = toMeters(&pos);
tankBodyDef.userData = tank;
b2Body *tankBody = _world->CreateBody(&tankBodyDef);
// Create shape definition and add body
shapeCache->addFixturesToBody(tankBody, "001/tank");
// Create sprite and add it to the layer
CCSprite *barrel = CCSprite::create();
//barrel->initWithFile("Tanks/001/barrel.png");
barrel->setPosition(CCPointMake(pos.x + 77, pos.y+117));
barrel->setTag(2);
this->addChild(barrel);
// Create barrel body
barrelBodyDef.type = b2_dynamicBody;
barrelBodyDef.userData = barrel;
barrelBodyDef.position = b2Vec2(tankBodyDef.position.x + 2.40625, tankBodyDef.position.y + 3.65625); // = same offset as joint!?!?!
b2Body *barrelBody = _world->CreateBody(&barrelBodyDef);
// Create shape definition and add body
shapeCache->addFixturesToBody(barrelBody, "001/barrel");
// Create a joint
//
b2RevoluteJointDef armJointDef;
//armJointDef.Initialize(tankBody, barrelBody, b2Vec2(400.0f/PTM_RATIO, 450/PTM_RATIO));
armJointDef.bodyA = tankBody;
armJointDef.bodyB = barrelBody;
armJointDef.localAnchorA.Set(2.40625, 3.65625);
armJointDef.localAnchorB.Set(-2.90625, -0.125);
armJointDef.enableMotor = true;
armJointDef.enableLimit = true;
armJointDef.motorSpeed = 10;
armJointDef.referenceAngle = CC_DEGREES_TO_RADIANS(0); // begin graden
armJointDef.lowerAngle = CC_DEGREES_TO_RADIANS(-50); // max graden naar beneden
armJointDef.upperAngle = CC_DEGREES_TO_RADIANS(00); // max graden naar boven
armJointDef.maxMotorTorque = 48;
armJoint = (b2RevoluteJoint*)_world->CreateJoint(&armJointDef);
I hope somebody got an answer :)
Problem solved :), i had to add the offset of the barrel anchor too, now it's on the right position.
Me and a friend of mine are trying to make a tank with cocos2dx.
we are so far that the tank is on the screen and the barrel is attached to the tank
but now we want to try to the rotate the barrel but nothing is happening, the joint is at the center where the barrel start en de dome ends. both the tank and the barrel are dynamic bodies and we are using a friction joint (see code)
// Create sprite and add it to the layer
CCSprite *tank = CCSprite::create();
//tank->initWithFile("../Resources/tanks/001/tank.png");
tank->setPosition(pos);
tank->setTag(1);
this->addChild(tank);
// Create ball body
b2BodyDef tankBodyDef;
tankBodyDef.type = b2_dynamicBody;
tankBodyDef.position = toMeters(&pos);
tankBodyDef.userData = tank;
tankBody = _world->CreateBody(&tankBodyDef);
// Create shape definition and add body
shapeCache->addFixturesToBody(tankBody, "001/tank");
pos = CCPointMake(580, 450);
// Create sprite and add it to the layer
CCSprite *barrel = CCSprite::create();
//barrel->initWithFile("Tanks/001/barrel.png");
barrel->setPosition(pos);
barrel->setTag(2);
this->addChild(barrel);
// Create ball body
b2BodyDef barrelBodyDef;
barrelBodyDef.type = b2_dynamicBody;
barrelBodyDef.position = toMeters(&pos);
barrelBodyDef.userData = barrel;
barrelBody = _world->CreateBody(&barrelBodyDef);
tankBarrelAnchor = CreateRevoluteJoint(tankBody, barrelBody, -85.f, 180.f, 2000000.f, 0.f, true, false);
tankBarrelAnchor->localAnchorA = b2Vec2(0, 0);
tankBarrelAnchor->localAnchorB = b2Vec2(0, 0);
tankBarrelAnchor->referenceAngle = 0;
joint = (b2RevoluteJoint*)_world->CreateJoint(tankBarrelAnchor);
b2RevoluteJointDef* Level::CreateRevoluteJoint(b2Body* A, b2Body* B, float lowerAngle, float upperAngle, float maxMotorTorque, float motorSpeed, boolean enableMotor, boolean collideConnect){
b2RevoluteJointDef *revoluteJointDef = new b2RevoluteJointDef();
revoluteJointDef->bodyA = A;
revoluteJointDef->bodyB = B;
revoluteJointDef->collideConnected = collideConnect;
revoluteJointDef->lowerAngle = CC_DEGREES_TO_RADIANS(lowerAngle);
revoluteJointDef->upperAngle = CC_DEGREES_TO_RADIANS(upperAngle);
revoluteJointDef->enableLimit = true;
revoluteJointDef->enableMotor = enableMotor;
revoluteJointDef->maxMotorTorque = maxMotorTorque;
revoluteJointDef->motorSpeed = CC_DEGREES_TO_RADIANS(motorSpeed); //1 turn per second counter-clockwise
return revoluteJointDef;
}
I think the problem is that your anchor positions are not correct. This setting:
tankBarrelAnchor->localAnchorA = b2Vec2(0, 0);
tankBarrelAnchor->localAnchorB = b2Vec2(0, 0);
... would put the anchors at those two red and green axes you can see in your screenshot, and it will try to pull those two points together. Try turning on the joints display in the debug draw and this should be more obvious.
You need to give the anchors as local coordinates from the point of view of each body. For example from the point of view of the tank body, the swivel point looks like (1,2) and from the point of view of the barrel body, it looks like (-1,0). Of course the dimensions you are using are probably different, but the directions should be somewhat similar.
See the "Local anchors" section here: http://www.iforce2d.net/b2dtut/joints-revolute
EDIT 2: Problem solved! I can´t promise it will work with different settings, but by putting my block´s body density to 0, the stack of blocks did not fall when new blocks are added.
I´m sorry about the poor title of the question, I´ll explain my problem closer here:
So, I´ve used Box2D and cocos2D to setup a simple project where two boxes stacks on top of each other (I´m planning to expand to 8-10 boxes). Right now, using a friction of 10.0f on each box, the box at the top still moves around a little. If I would add more boxes, the "tower" would fall and I don´t want that.
I want the boxes to use the gravity to move down, but I never ever want them to change there start x-value.
So, how could I prevent my tower of boxes to fall over or prevent my boxes from moving in x-direction?
EDIT: Posting some code
This code creates on of the boxes, the other one just have a different sprite file.
CCSprite *block = [CCSprite spriteWithFile:#"red.png"];
block.position = ccp(200,380);
[self addChild:block];
//Body definition
b2BodyDef blockDef;
blockDef.type = b2_dynamicBody;
blockDef.position.Set(200/PTM_RATIO, 200/PTM_RATIO);
blockDef.userData = block;
b2Body *blockBody = _world->CreateBody(&blockDef);
//Create the shape
b2PolygonShape blockShape;
blockShape.SetAsBox(block.contentSize.width/PTM_RATIO/2, block.contentSize.height/PTM_RATIO/2);
//Fixture defintion
b2FixtureDef blockFixtureDef;
blockFixtureDef.shape = &blockShape;
blockFixtureDef.restitution = 0.0f;
blockFixtureDef.density = 10.0f;
blockFixtureDef.friction = 10.0f;
_redBlockFixture = blockBody->CreateFixture(&blockFixtureDef);
Nothing fancy.
Regards.
You could setup a 2 (1 pixel wide) walls in box2D to the left and right of the block. Here's some sample code for the left wall. To create the right wall, just copy and past the code and change the variable names and the position of the BodyDef.
// Constant you'll need to define
float wallHeight;
// Create wall body
b2BodyDef wallBodyDef;
wallBodyDef.type = b2_dynamicBody;
wallBodyDef.position.Set(200 - block.contentSize.width/PTM_RATIO/2, 0);
b2Body *wallBody = _world->CreateBody(&wallBodyDef);
// Create wall shape
b2PolygonShape wallShape;
wallShape.SetAsBox(1, wallHeight);
// Create shape definition and add to body
b2FixtureDef wallShapeDef;
wallShapeDef.shape = &wallShape;
wallShapeDef.density = 100.0f;
wallShapeDef.friction = 0.0f;
wallShapeDef.restitution = 0.0f;
b2Fixture *wallFixture = wallBody->CreateFixture(&wallShapeDef);
I solved this problem by adjusting the restitution (bounce) of the static surface upon which the blocks are stacked. For example, if the floor has a restitution of .2, a stack of five blocks will look like they are compressing into each other, and eventually topple:
Set the restitution of the floor to 0, and the blocks stay stacked the way you would expect: