我正在尝试学习如何对特定对象实施径向重力，我正在使用（http://www.vellios.com/2010/06/11/radial-gravity-w-box2d-source/）上的教程，但是本教程是用旧版本的 Cocos2d 编写的。我已尽力修复它。如果有人能指出我正确的方向，我将不胜感激。这是我到目前为止所拥有的。我评论了我遇到问题的地方。谢谢你。
HelloWorldLayer.h
#import <GameKit/GameKit.h>
// When you import this file, you import all the cocos2d classes
#import "cocos2d.h"
#import "Box2D.h"
#import "GLES-Render.h"
#define PTM_RATIO 32
// HelloWorldLayer
@interface HelloWorldLayer : CCLayer <GKAchievementViewControllerDelegate, GKLeaderboardViewControllerDelegate>
{
b2World* world; // strong ref
GLESDebugDraw *m_debugDraw; // strong ref
}
// returns a CCScene that contains the HelloWorldLayer as the only child
+(CCScene *) scene;
@end
HelloWorldLayer.mm
// Import the interfaces
#import "HelloWorldLayer.h"
// Needed to obtain the Navigation Controller
#import "AppDelegate.h"
#define PTM_RATIO 32
#define kRADIAL_GRAVITY_FORCE 250.0f
enum {
kTagParentNode = 1,
kTagTileMap = 1,
kTagSpriteSheet = 1,
kTagAnimation1 = 1,
};
#pragma mark - HelloWorldLayer
@interface HelloWorldLayer()
-(void) initPhysics;
-(void) addNewSpriteAtPosition:(CGPoint)p;
-(void) createMenu;
@end
@implementation HelloWorldLayer
+(CCScene *) scene
{
// 'scene' is an autorelease object.
CCScene *scene = [CCScene node];
// 'layer' is an autorelease object.
HelloWorldLayer *layer = [HelloWorldLayer node];
// add layer as a child to scene
[scene addChild: layer];
// return the scene
return scene;
}
-(id) init
{
if( (self=[super init])) {
// enable events
self.isTouchEnabled = YES;
self.isAccelerometerEnabled = YES;
CGSize screenSize = [CCDirector sharedDirector].winSize;
CCLOG(@"Screen width %0.2f screen height %0.2f",screenSize.width,screenSize.height);
b2Vec2 gravity;
gravity.Set(0.0f, -10.0f);
// This will speed up the physics simulation
bool doSleep = true;
// Construct a world object, which will hold and simulate the rigid bodies.
world = new b2World(gravity);
world->SetAllowSleeping(doSleep);
world->SetContinuousPhysics(true);
//Set up sprite
CCSprite *sheet = [CCSprite spriteWithFile:@"blocks.png"];
[self addChild:sheet z:0 tag:kTagSpriteSheet];
[self addNewSpriteAtPosition:ccp(screenSize.width/2, screenSize.height/2)];
//ERROR Use of undeclared identifier 'CCLabel'
//ERROR Use of undeclared identifier 'label'
CCLabel *label = [CCLabel labelWithString:@"Tap Screen" fontName:@"Marker Felt" fontSize:32];
// ERROR Use of undeclared identifier 'label'
[self addChild:label z:0];
//ERROR Use of undeclared identifier 'label'
[label setColor:ccc3(0,0,255)];
//ERROR Use of undeclared identifier 'label'
label.position = ccp( screenSize.width/2, screenSize.height-50);
// Create our static "Planet" - Nick
b2CircleShape shape;
shape.m_radius = 1.0f;
shape.m_p.Set(8.0f, 8.0f);
b2FixtureDef fd;
fd.shape = &shape;
//ERROR Use of undeclared identifier 'planet'
planet = groundBody->CreateFixture(&fd);
// End Create Planet - Nick
[self schedule: @selector(tick:)];
// init physics
[self initPhysics];
[self scheduleUpdate];
}
return self;
}
-(void) dealloc
{
delete world;
world = NULL;
delete m_debugDraw;
m_debugDraw = NULL;
[super dealloc];
}
-(void) createMenu
{
}
-(void) initPhysics
{
CGSize s = [[CCDirector sharedDirector] winSize];
b2Vec2 gravity;
gravity.Set(0.0f, -10.0f);
world = new b2World(gravity);
// Do we want to let bodies sleep?
world->SetAllowSleeping(true);
world->SetContinuousPhysics(true);
// Debug Draw functions
m_debugDraw = new GLESDebugDraw( PTM_RATIO );
world->SetDebugDraw(m_debugDraw);
uint32 flags = 0;
flags += b2Draw::e_shapeBit;
// flags += b2Draw::e_jointBit;
// flags += b2Draw::e_aabbBit;
// flags += b2Draw::e_pairBit;
// flags += b2Draw::e_centerOfMassBit;
m_debugDraw->SetFlags(flags);
// Define the ground body.
b2BodyDef groundBodyDef;
groundBodyDef.position.Set(0, 0); // bottom-left corner
// Call the body factory which allocates memory for the ground body
// from a pool and creates the ground box shape (also from a pool).
// The body is also added to the world.
b2Body* groundBody = world->CreateBody(&groundBodyDef);
// Define the ground box shape.
b2EdgeShape groundBox;
// bottom
groundBox.Set(b2Vec2(0,0), b2Vec2(s.width/PTM_RATIO,0));
groundBody->CreateFixture(&groundBox,0);
// top
groundBox.Set(b2Vec2(0,s.height/PTM_RATIO), b2Vec2(s.width/PTM_RATIO,s.height/PTM_RATIO));
groundBody->CreateFixture(&groundBox,0);
// left
groundBox.Set(b2Vec2(0,s.height/PTM_RATIO), b2Vec2(0,0));
groundBody->CreateFixture(&groundBox,0);
// right
groundBox.Set(b2Vec2(s.width/PTM_RATIO,s.height/PTM_RATIO), b2Vec2(s.width/PTM_RATIO,0));
groundBody->CreateFixture(&groundBox,0);
}
-(void) draw
{
//
// IMPORTANT:
// This is only for debug purposes
// It is recommend to disable it
//
[super draw];
// Default GL states: GL_TEXTURE_2D, GL_VERTEX_ARRAY, GL_COLOR_ARRAY, GL_TEXTURE_COORD_ARRAY
// Needed states: GL_VERTEX_ARRAY,
// Unneeded states: GL_TEXTURE_2D, GL_COLOR_ARRAY, GL_TEXTURE_COORD_ARRAY
glDisable(GL_TEXTURE_2D);
glDisable(GL_COLOR_BUFFER_BIT);
world->DrawDebugData();
}
-(void) addNewSpriteAtPosition:(CGPoint)p
{
CCLOG(@"Add sprite %0.2f x %02.f",p.x,p.y);
CCSprite *sheet = (CCSprite*) [self getChildByTag:kTagSpriteSheet];
int idx = (CCRANDOM_0_1() > .5 ? 0:1);
int idy = (CCRANDOM_0_1() > .5 ? 0:1);
//ERROR Cannot initialize a parameter of type 'CCTexture2D *' with an lvalue of type 'CCSprite *'
CCSprite *sprite = [CCSprite spriteWithTexture:sheet rect:CGRectMake(32 * idx,32 * idy,32,32)];
[sheet addChild:sprite];
sprite.position = ccp( 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);
bodyDef.userData = sprite;
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);
}
-(void) update: (ccTime) dt
{
//It is recommended that a fixed time step is used with Box2D for stability
//of the simulation, however, we are using a variable time step here.
//You need to make an informed choice, the following URL is useful
//http://gafferongames.com/game-physics/fix-your-timestep/
int32 velocityIterations = 8;
int32 positionIterations = 1;
// Instruct the world to perform a single step of simulation. It is
// generally best to keep the time step and iterations fixed.
world->Step(dt, velocityIterations, positionIterations);
//Iterate over the bodies in the physics world
for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())
{
b2Body* ground = planet->GetBody();
b2CircleShape* circle = (b2CircleShape*)planet->GetShape();
// Get position of our "Planet" - Nick
b2Vec2 center = ground->GetWorldPoint(circle->m_p);
// Get position of our current body in the iteration - Nick
b2Vec2 position = b->GetPosition();
// Get the distance between the two objects. - Nick
b2Vec2 d = center - position;
// The further away the objects are, the weaker the gravitational force is - Nick
float force = kRADIAL_GRAVITY_FORCE / d.LengthSquared(); // 150 can be changed to adjust the amount of force - Nick
d.Normalize();
b2Vec2 F = force * d;
// Finally apply a force on the body in the direction of the "Planet" - Nick
b->ApplyForce(F, position);
if (b->GetUserData() != NULL) {
//Synchronize the AtlasSprites position and rotation with the corresponding body
CCSprite *myActor = (CCSprite*)b->GetUserData();
myActor.position = CGPointMake( b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO);
myActor.rotation = -1 * CC_RADIANS_TO_DEGREES(b->GetAngle());
}
}
}
- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
//Add a new body/atlas sprite at the touched location
for( UITouch *touch in touches ) {
CGPoint location = [touch locationInView: [touch view]];
location = [[CCDirector sharedDirector] convertToGL: location];
[self addNewSpriteAtPosition:location];
}
}
- (void)accelerometer:(UIAccelerometer*)accelerometer didAccelerate:(UIAcceleration*)acceleration
{
static float prevX=0, prevY=0;
//#define kFilterFactor 0.05f
#define kFilterFactor 1.0f // don't use filter. the code is here just as an example
float accelX = (float) acceleration.x * kFilterFactor + (1- kFilterFactor)*prevX;
float accelY = (float) acceleration.y * kFilterFactor + (1- kFilterFactor)*prevY;
prevX = accelX;
prevY = accelY;
// accelerometer values are in "Portrait" mode. Change them to Landscape left
// multiply the gravity by 10
b2Vec2 gravity( -accelY * 10, accelX * 10);
world->SetGravity( gravity );
}
#pragma mark GameKit delegate
-(void) achievementViewControllerDidFinish:(GKAchievementViewController *)viewController
{
AppController *app = (AppController*) [[UIApplication sharedApplication] delegate];
[[app navController] dismissModalViewControllerAnimated:YES];
}
-(void) leaderboardViewControllerDidFinish:(GKLeaderboardViewController *)viewController
{
AppController *app = (AppController*) [[UIApplication sharedApplication] delegate];
[[app navController] dismissModalViewControllerAnimated:YES];
}
@end