如何使用Box2D和Cocos2D制作一款像Fruit Ninja一样的游戏-第2部分

// Add inside the @interface
BOOL _sliceEntered;
BOOL _sliceExited;
b2Vec2 _entryPoint;
b2Vec2 _exitPoint;
double _sliceEntryTime;// Add after the @interface
@property(nonatomic,readwrite)BOOL sliceEntered;
@property(nonatomic,readwrite)BOOL sliceExited;
@property(nonatomic,readwrite)b2Vec2 entryPoint;
@property(nonatomic,readwrite)b2Vec2 exitPoint;
@property(nonatomic,readwrite)double sliceEntryTime;

// Add inside the @implementation
@synthesize entryPoint = _entryPoint;
@synthesize exitPoint = _exitPoint;
@synthesize sliceEntered = _sliceEntered;
@synthesize sliceExited = _sliceExited;
@synthesize sliceEntryTime = _sliceEntryTime;// Add inside the initWithTexture method, inside the if statement
_sliceExited = NO;
_sliceEntered = NO;
_entryPoint.SetZero();
_exitPoint.SetZero();
_sliceExited = 0;

CGPoint _startPoint;
CGPoint _endPoint;

// Add inside the draw method after kmGLPushMatrix()
ccDrawLine(_startPoint, _endPoint);// Add this method
-(void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{for (UITouch *touch in touches){CGPoint location = [touch locationInView:[touch view]];location = [[CCDirector sharedDirector] convertToGL:location];_startPoint = location;_endPoint = location;}
}// Add this method
- (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{for (UITouch *touch in touches){CGPoint location = [touch locationInView:[touch view]];location = [[CCDirector sharedDirector] convertToGL:location];_endPoint = location;}
}

#ifndef CutCutCut_RaycastCallback_h
#define CutCutCut_RaycastCallback_h#import "Box2D.h"
#import "PolygonSprite.h"class RaycastCallback : public b2RayCastCallback
{
public:
RaycastCallback(){
}float32 ReportFixture(b2Fixture *fixture,const b2Vec2 &point,const b2Vec2 &normal,float32 fraction)
{PolygonSprite *ps = (PolygonSprite*)fixture->GetBody()->GetUserData();if (!ps.sliceEntered){ps.sliceEntered = YES;//you need to get the point coordinates within the shapeps.entryPoint  = ps.body->GetLocalPoint(point);ps.sliceEntryTime = CACurrentMediaTime() + 1;CCLOG(@"Slice Entered at world coordinates:(%f,%f), polygon coordinates:(%f,%f)", point.x*PTM_RATIO, point.y*PTM_RATIO, ps.entryPoint.x*PTM_RATIO, ps.entryPoint.y*PTM_RATIO);}else if (!ps.sliceExited){ps.exitPoint = ps.body->GetLocalPoint(point);ps.sliceExited = YES;CCLOG(@"Slice Exited at world coordinates:(%f,%f), polygon coordinates:(%f,%f)", point.x*PTM_RATIO, point.y*PTM_RATIO, ps.exitPoint.x*PTM_RATIO, ps.exitPoint.y*PTM_RATIO);}return 1;
}
};#endif

// Add to top of file
#import "RaycastCallback.h"// Add inside the @interface
RaycastCallback *_raycastCallback;

// Add inside the init method, right after [self initSprites]
_raycastCallback = new RaycastCallback();// Add at the end of the ccTouchesEnded method
world->RayCast(_raycastCallback, b2Vec2(_startPoint.x / PTM_RATIO, _startPoint.y / PTM_RATIO),b2Vec2(_endPoint.x / PTM_RATIO, _endPoint.y / PTM_RATIO));world->RayCast(_raycastCallback, b2Vec2(_endPoint.x / PTM_RATIO, _endPoint.y / PTM_RATIO),b2Vec2(_startPoint.x / PTM_RATIO, _startPoint.y / PTM_RATIO));

// Add to top of file
#define calculate_determinant_2x2(x1,y1,x2,y2) x1*y2-y1*x2
#define calculate_determinant_2x3(x1,y1,x2,y2,x3,y3) x1*y2+x2*y3+x3*y1-y1*x2-y2*x3-y3*x1// Add after the properties
-(b2Vec2*)arrangeVertices:(b2Vec2*)vertices count:(int)count;
-(void)splitPolygonSprite:(PolygonSprite*)sprite;
-(BOOL)areVerticesAcceptable:(b2Vec2*)vertices count:(int)count;
-(b2Body*)createBodyWithPosition:(b2Vec2)position rotation:(float)rotation vertices:(b2Vec2*)vertices vertexCount:(int32)count density:(float)density friction:(float)friction restitution:(float)restitution;

-(void)splitPolygonSprite:(PolygonSprite*)sprite
{//declare & initialize variables to be used for laterPolygonSprite *newSprite1, *newSprite2;//our original shape's attributesb2Fixture *originalFixture = sprite.body->GetFixtureList();b2PolygonShape *originalPolygon = (b2PolygonShape*)originalFixture->GetShape();int vertexCount = originalPolygon->GetVertexCount();//our determinant(to be described later) and iteratorfloat determinant;int i;//you store the vertices of our two new sprites hereb2Vec2 *sprite1Vertices = (b2Vec2*)calloc(24, sizeof(b2Vec2));b2Vec2 *sprite2Vertices = (b2Vec2*)calloc(24, sizeof(b2Vec2));b2Vec2 *sprite1VerticesSorted, *sprite2VerticesSorted;//you store how many vertices there are for each of the two new sprites hereint sprite1VertexCount = 0;int sprite2VertexCount = 0;//step 1://the entry and exit point of our cut are considered vertices of our two new shapes, so you add these before anything elsesprite1Vertices[sprite1VertexCount++] = sprite.entryPoint;sprite1Vertices[sprite1VertexCount++] = sprite.exitPoint;sprite2Vertices[sprite2VertexCount++] = sprite.entryPoint;sprite2Vertices[sprite2VertexCount++] = sprite.exitPoint;//step 2://iterate through all the vertices and add them to each sprite's shapefor (i=0; i<vertexCount; i++){//get our vertex from the polygonb2Vec2 point = originalPolygon->GetVertex(i);//you check if our point is not the same as our entry or exit point firstb2Vec2 diffFromEntryPoint = point - sprite.entryPoint;b2Vec2 diffFromExitPoint = point - sprite.exitPoint;if ((diffFromEntryPoint.x == 0 && diffFromEntryPoint.y == 0) || (diffFromExitPoint.x == 0 && diffFromExitPoint.y == 0)){}else {determinant = calculate_determinant_2x3(sprite.entryPoint.x, sprite.entryPoint.y, sprite.exitPoint.x, sprite.exitPoint.y, point.x, point.y);if (determinant > 0){//if the determinant is positive, then the three points are in clockwise ordersprite1Vertices[sprite1VertexCount++] = point;}else{//if the determinant is 0, the points are on the same line. if the determinant is negative, then they are in counter-clockwise ordersprite2Vertices[sprite2VertexCount++] = point;}//endif}//endif}//endfor//step 3://Box2D needs vertices to be arranged in counter-clockwise order so you reorder our points using a custom functionsprite1VerticesSorted = [self arrangeVertices:sprite1Vertices count:sprite1VertexCount];sprite2VerticesSorted = [self arrangeVertices:sprite2Vertices count:sprite2VertexCount];//step 4://Box2D has some restrictions with defining shapes, so you have to consider these. You only cut the shape if both shapes pass certain requirements from our functionBOOL sprite1VerticesAcceptable = [self areVerticesAcceptable:sprite1VerticesSorted count:sprite1VertexCount];BOOL sprite2VerticesAcceptable = [self areVerticesAcceptable:sprite2VerticesSorted count:sprite2VertexCount];//step 5://you destroy the old shape and create the new shapes and spritesif (sprite1VerticesAcceptable && sprite2VerticesAcceptable){//create the first sprite's body        b2Body *body1 = [self createBodyWithPosition:sprite.body->GetPosition() rotation:sprite.body->GetAngle() vertices:sprite1VerticesSorted vertexCount:sprite1VertexCount density:originalFixture->GetDensity() friction:originalFixture->GetFriction() restitution:originalFixture->GetRestitution()];//create the first spritenewSprite1 = [PolygonSprite spriteWithTexture:sprite.texture body:body1 original:NO];[self addChild:newSprite1 z:1];//create the second sprite's bodyb2Body *body2 = [self createBodyWithPosition:sprite.body->GetPosition() rotation:sprite.body->GetAngle() vertices:sprite2VerticesSorted vertexCount:sprite2VertexCount density:originalFixture->GetDensity() friction:originalFixture->GetFriction() restitution:originalFixture->GetRestitution()];//create the second spritenewSprite2 = [PolygonSprite spriteWithTexture:sprite.texture body:body2 original:NO];[self addChild:newSprite2 z:1];//you don't need the old shape & sprite anymore so you either destroy it or squirrel it awayif (sprite.original){   [sprite deactivateCollisions];sprite.position = ccp(-256,-256);   //cast them farawaysprite.sliceEntered = NO;sprite.sliceExited = NO;sprite.entryPoint.SetZero();sprite.exitPoint.SetZero();}else {world->DestroyBody(sprite.body);[self removeChild:sprite cleanup:YES];}}else{sprite.sliceEntered = NO;sprite.sliceExited = NO;}//free up our allocated vectorsfree(sprite1VerticesSorted);free(sprite2VerticesSorted);free(sprite1Vertices);free(sprite2Vertices);
}

// Add before the @implementation
int comparator(const void *a, const void *b) {const b2Vec2 *va = (const b2Vec2 *)a;const b2Vec2 *vb = (const b2Vec2 *)b;if (va->x > vb->x) {return 1;} else if (va->x < vb->x) {return -1;}return 0;    
}// Add these methods
-(b2Body*)createBodyWithPosition:(b2Vec2)position rotation:(float)rotation vertices:(b2Vec2*)vertices vertexCount:(int32)count density:(float)density friction:(float)friction restitution:(float)restitution
{b2BodyDef bodyDef;bodyDef.type = b2_dynamicBody;bodyDef.position = position;bodyDef.angle = rotation;b2Body *body = world->CreateBody(&bodyDef);b2FixtureDef fixtureDef;fixtureDef.density = density;fixtureDef.friction = friction;fixtureDef.restitution = restitution;b2PolygonShape shape;shape.Set(vertices, count);fixtureDef.shape = &shape;body->CreateFixture(&fixtureDef);return body;
}-(b2Vec2*)arrangeVertices:(b2Vec2*)vertices count:(int)count
{float determinant;int iCounterClockWise = 1;int iClockWise = count - 1;int i;b2Vec2 referencePointA,referencePointB;b2Vec2 *sortedVertices = (b2Vec2*)calloc(count, sizeof(b2Vec2));//sort all vertices in ascending order according to their x-coordinate so you can get two points of a lineqsort(vertices, count, sizeof(b2Vec2), comparator);sortedVertices[0] = vertices[0];referencePointA = vertices[0];          //leftmost pointreferencePointB = vertices[count-1];    //rightmost point//you arrange the points by filling our vertices in both clockwise and counter-clockwise directions using the determinant functionfor (i=1;i<count-1;i++){determinant = calculate_determinant_2x3(referencePointA.x, referencePointA.y, referencePointB.x, referencePointB.y, vertices[i].x, vertices[i].y);if (determinant<0){sortedVertices[iCounterClockWise++] = vertices[i];}else {sortedVertices[iClockWise--] = vertices[i];}//endif}//endifsortedVertices[iCounterClockWise] = vertices[count-1];return sortedVertices;
}-(BOOL)areVerticesAcceptable:(b2Vec2*)vertices count:(int)count
{return YES;
}

// Add this method
-(void)checkAndSliceObjects
{double curTime = CACurrentMediaTime();for (b2Body* b = world->GetBodyList(); b; b = b->GetNext()){if (b->GetUserData() != NULL) {PolygonSprite *sprite = (PolygonSprite*)b->GetUserData();if (sprite.sliceEntered && curTime > sprite.sliceEntryTime) {sprite.sliceEntered = NO;}else if (sprite.sliceEntered && sprite.sliceExited){[self splitPolygonSprite:sprite];}}}
}// Add this in the update method
[self checkAndSliceObjects];

// Add this method
-(void)clearSlices
{for (b2Body* b = world->GetBodyList(); b; b = b->GetNext()){if (b->GetUserData() != NULL) {PolygonSprite *sprite = (PolygonSprite*)b->GetUserData();sprite.sliceEntered = NO;sprite.sliceExited = NO;}}
}// Add this at the end of ccTouchesMoved
if (ccpLengthSQ(ccpSub(_startPoint, _endPoint)) > 25)
{world->RayCast(_raycastCallback, b2Vec2(_startPoint.x / PTM_RATIO, _startPoint.y / PTM_RATIO),b2Vec2(_endPoint.x / PTM_RATIO, _endPoint.y / PTM_RATIO));world->RayCast(_raycastCallback, b2Vec2(_endPoint.x / PTM_RATIO, _endPoint.y / PTM_RATIO),b2Vec2(_startPoint.x / PTM_RATIO, _startPoint.y / PTM_RATIO));_startPoint = _endPoint;
}// Remove these from ccTouchesEnded
world->RayCast(_raycastCallback, b2Vec2(_startPoint.x / PTM_RATIO, _startPoint.y / PTM_RATIO),b2Vec2(_endPoint.x / PTM_RATIO, _endPoint.y / PTM_RATIO));world->RayCast(_raycastCallback, b2Vec2(_endPoint.x / PTM_RATIO, _endPoint.y / PTM_RATIO),b2Vec2(_startPoint.x / PTM_RATIO, _startPoint.y / PTM_RATIO));// Add this inside ccTouchesEnded
[self clearSlices];

// Remove the CCLOG commands// Add to top of file
#define collinear(x1,y1,x2,y2,x3,y3) fabsf((y1-y2) * (x1-x3) - (y1-y3) * (x1-x2))// Remove this line from the else if statement
ps.sliceExited = YES;// Add this inside the else if statement, right after setting the exitPoint
b2Vec2 entrySide = ps.entryPoint - ps.centroid;
b2Vec2 exitSide = ps.exitPoint - ps.centroid;if (entrySide.x * exitSide.x < 0 || entrySide.y * exitSide.y < 0)
{ps.sliceExited = YES;
}
else {//if the cut didn't cross the centroid, you check if the entry and exit point lie on the same lineb2Fixture *fixture = ps.body->GetFixtureList();b2PolygonShape *polygon = (b2PolygonShape*)fixture->GetShape();int count = polygon->GetVertexCount();BOOL onSameLine = NO;for (int i = 0 ; i < count; i++){b2Vec2 pointA = polygon->GetVertex(i);b2Vec2 pointB;if (i == count - 1){pointB = polygon->GetVertex(0);}else {pointB = polygon->GetVertex(i+1);}//endiffloat collinear = collinear(pointA.x,pointA.y, ps.entryPoint.x, ps.entryPoint.y, pointB.x,pointB.y);if (collinear <= 0.00001){float collinear2 = collinear(pointA.x,pointA.y,ps.exitPoint.x,ps.exitPoint.y,pointB.x,pointB.y);if (collinear2 <= 0.00001){onSameLine = YES;}break;}//endif}//endforif (onSameLine){ps.entryPoint = ps.exitPoint;ps.sliceEntryTime = CACurrentMediaTime() + 1;ps.sliceExited = NO;}else {ps.sliceExited = YES;}//endif
}

-(BOOL)areVerticesAcceptable:(b2Vec2*)vertices count:(int)count
{//check 1: polygons need to at least have 3 verticesif (count < 3){return NO;}//check 2: the number of vertices cannot exceed b2_maxPolygonVerticesif (count > b2_maxPolygonVertices){return NO;}//check 3: Box2D needs the distance from each vertex to be greater than b2_epsilonint32 i;for (i=0; i<count; ++i){int32 i1 = i;int32 i2 = i + 1 < count ? i + 1 : 0;b2Vec2 edge = vertices[i2] - vertices[i1];if (edge.LengthSquared() <= b2_epsilon * b2_epsilon){return NO;}}//check 4: Box2D needs the area of a polygon to be greater than b2_epsilonfloat32 area = 0.0f;b2Vec2 pRef(0.0f,0.0f);for (i=0; i<count; ++i){b2Vec2 p1 = pRef;b2Vec2 p2 = vertices[i];b2Vec2 p3 = i + 1 < count ? vertices[i+1] : vertices[0];b2Vec2 e1 = p2 - p1;b2Vec2 e2 = p3 - p1;float32 D = b2Cross(e1, e2);float32 triangleArea = 0.5f * D;area += triangleArea;}if (area <= 0.0001){return NO;}//check 5: Box2D requires that the shape be Convex.float determinant;float referenceDeterminant;b2Vec2 v1 = vertices[0] - vertices[count-1];b2Vec2 v2 = vertices[1] - vertices[0];referenceDeterminant = calculate_determinant_2x2(v1.x, v1.y, v2.x, v2.y);for (i=1; i<count-1; i++){v1 = v2;v2 = vertices[i+1] - vertices[i];determinant = calculate_determinant_2x2(v1.x, v1.y, v2.x, v2.y);//you use the determinant to check direction from one point to another. A convex shape's points should only go around in one direction. The sign of the determinant determines that direction. If the sign of the determinant changes mid-way, then you have a concave shape.if (referenceDeterminant * determinant < 0.0f){//if multiplying two determinants result to a negative value, you know that the sign of both numbers differ, hence it is concavereturn NO;}}v1 = v2;v2 = vertices[0]-vertices[count-1];determinant = calculate_determinant_2x2(v1.x, v1.y, v2.x, v2.y);if (referenceDeterminant * determinant < 0.0f){return NO;}return YES;
}

// Comment these out from the draw method
ccDrawLine(_startPoint, _endPoint);
world->DrawDebugData();// Add inside the init method
[self initBackground];// Add this method
-(void)initBackground
{CGSize screen = [[CCDirector sharedDirector] winSize];CCSprite *background = [CCSprite spriteWithFile:@"bg.png"];background.position = ccp(screen.width/2,screen.height/2);[self addChild:background z:0];
}

// Replace everything starting from glDisableClientState in the draw method with this
CC_NODE_DRAW_SETUP();ccGLBlendFunc( CC_BLEND_SRC, CC_BLEND_DST );ccGLBindTexture2D( [_texture name] );    
glVertexAttribPointer(kCCVertexAttrib_Position, 2, GL_FLOAT, GL_FALSE, sizeof(vertices[0]), vertices);
glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, sizeof(coordinates[0]), coordinates);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 2*[path count]-2);// Add inside the initWithMaximumPoint method
self.shaderProgram = [[CCShaderCache sharedShaderCache] programForKey:kCCShader_PositionTexture];// Remove from the setWidth method
* CC_CONTENT_SCALE_FACTOR()// Remove from the push method
if (CC_CONTENT_SCALE_FACTOR() != 1.0f) {v = ccpMult(v, CC_CONTENT_SCALE_FACTOR());
}

@property(nonatomic,retain)NSMutableArray *path;

@synthesize path;

// Add to top of file
#import "CCBlade.h"// Add inside the @interface
CCArray *_blades;
CCBlade *_blade;
float _deltaRemainder;// Add after the @interface
@property(nonatomic,retain)CCArray *blades;

// Add inside the @implementation
@synthesize blades = _blades;// Add inside dealloc
[_blades release];
_blades = nil;// Add inside init, after _raycastCallback
_deltaRemainder = 0.0;
_blades = [[CCArray alloc] initWithCapacity:3];
CCTexture2D *texture = [[CCTextureCache sharedTextureCache] addImage:@"streak.png"];for (int i = 0; i < 3; i++)
{CCBlade *blade = [CCBlade bladeWithMaximumPoint:50];blade.autoDim = NO;blade.texture = texture;[self addChild:blade z:2];[_blades addObject:blade];
}// Add inside update, right after [self checkAndSliceObjects]
if ([_blade.path count] > 3) {_deltaRemainder+=dt*60*1.2;int pop = (int)roundf(_deltaRemainder);_deltaRemainder-=pop;[_blade pop:pop];
}// Add inside ccTouchesBegan
CCBlade *blade;
CCARRAY_FOREACH(_blades, blade)
{if (blade.path.count == 0){_blade = blade;[_blade push:location];break;}
}// Add inside ccTouchesMoved
[_blade push:location];// Add inside ccTouchesEnded
[_blade dim:YES];