落書き – 五角形を落とす Box2d

概要

五角形等のポリゴンをBox2dを使って表示してみる。

(XcodeのiOS6 iPhone Simulatorで試しています。)

ポイント

・PanGestureRecognizerをつかって指で移動させる

・PolygonShapeのSet(points, 5) で五角形

Box2d導入手順

次のアドレスからソースを取得

svn checkout http://box2d.googlecode.com/svn/trunk/ box2d-read-only

1. Box2Dをプロジェクトに組み込む

Xcodeメニューの File -> Add File

2. C++ で書く。Fileの拡張子を変更

Box2dを使うソースの拡張子を mm に

3. Box2Dを import できるように Search Pathを追加

Build Settings (All) の Search Pathsのなかの Header Search Paths

サンプルコード

#import <Box2D/Box2D.h>

#import “ViewController.h”

// PolygonMesh

@interface PolygonMesh : UIView

@property (nonatomic, assign) CGPoint p1,p2,p3,p4,p5;

@end

@implementation PolygonMesh

@synthesize p1,p2,p3,p4,p5;

– (id)initWithFrame:(CGRect)frame

{

self = [super initWithFrame:frame];

if (self) {

self.backgroundColor = [UIColor clearColor];

}

return self;

}

-(void)drawRect:(CGRect)rect

{

CGContextRef ctx = UIGraphicsGetCurrentContext();

[[UIColor redColor] set];

CGContextSetLineWidth(ctx, 2.0);

NSArray *arr = [NSArray arrayWithObjects:[NSValue valueWithCGPoint:p1],[NSValue valueWithCGPoint:p2],[NSValue valueWithCGPoint:p3],[NSValue valueWithCGPoint:p4],[NSValue valueWithCGPoint:p5], nil];

for (int i=1; i<[arr count] + 1; i++) {

CGPoint start = [[arr objectAtIndex:i-1] CGPointValue];

CGPoint end = [[arr objectAtIndex:i % ([arr count])] CGPointValue];

if (!CGPointEqualToPoint(end,CGPointZero)) {

CGContextMoveToPoint(ctx, start.x, start.y);

CGContextAddLineToPoint(ctx, end.x, end.y);

CGContextStrokePath(ctx);

CGContextFillEllipseInRect(ctx, CGRectMake(end.x–4, end.y–4, 8, 8));

}

@end

// ViewController

#define PTM_RATIO 16.0

@interface ViewController () {

b2World *world;

NSTimer *timer;

int status;

}

@end

@implementation ViewController

– (void)viewDidLoad

{

self.view.backgroundColor = [UIColor blackColor];

[super viewDidLoad];

[self createWorld];

[self createPolygons];

[self start];

}

-(void)createWorld

{

CGSize screenSize = self.view.bounds.size;

// 重力

b2Vec2 gravity;

gravity.Set(0.0f, –9.81f);

// ワールドオブジェクト

world = new b2World(gravity);

world->SetContinuousPhysics(true);

b2BodyDef groundBodyDef;

groundBodyDef.position.Set(0, 0); // bottom-left corner

b2Body* groundBody = world->CreateBody(&groundBodyDef);

b2EdgeShape groundBox;

groundBox.Set(b2Vec2(0,0), b2Vec2(screenSize.width/PTM_RATIO,0));

groundBody->CreateFixture(&groundBox, 0);

groundBox.Set(b2Vec2(0,screenSize.height/PTM_RATIO), b2Vec2(0,0));

groundBody->CreateFixture(&groundBox, 0);

groundBox.Set(b2Vec2(screenSize.width/PTM_RATIO,screenSize.height/PTM_RATIO), b2Vec2(screenSize.width/PTM_RATIO,0));

groundBody->CreateFixture(&groundBox, 0);

}

// 五角形を作る

– (void)createPolygons

{

// Viewを用意

float r = 45;

float angle = M_PI / 2.5;

PolygonMesh *pentagon = [[PolygonMesh alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];

pentagon.p1 = CGPointMake(r*cos(angle)+50, r*sin(angle)+50);

pentagon.p2 = CGPointMake(r*cos(angle*2)+50, r*sin(angle*2)+50);

pentagon.p3 = CGPointMake(r*cos(angle*3)+50, r*sin(angle*3)+50);

pentagon.p4 = CGPointMake(r*cos(angle*4)+50, r*sin(angle*4)+50);

pentagon.p5 = CGPointMake(r*cos(angle*5)+50, r*sin(angle*5)+50);

[self.view addSubview:pentagon];

UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(tap:)];

[pentagon addGestureRecognizer:pan];

// Box2dとViewを連携

b2BodyDef bodyDef;

bodyDef.type = b2_dynamicBody;

CGPoint p = pentagon.center;

bodyDef.position.Set(p.x/PTM_RATIO, (self.view.bounds.size.height – p.y)/PTM_RATIO);

bodyDef.userData = (__bridge void *)pentagon;

b2Body *body = world->CreateBody(&bodyDef);

b2Vec2 points[5];

float x,y;

CGPoint wp;

wp = pentagon.p1;

x = (wp.x – pentagon.center.x) / PTM_RATIO;