シェルピンスキー四面体を表示するiPhoneアプリのサンプルコードを描いてみます。
#import “ViewController.h”
@import SceneKit;
@interface ViewController ()
@property (nonatomic, weak) SCNView *sceneView;
@property (nonatomic ,weak) SCNNode *current;
@property (nonatomic) int count;
@end
@implementation ViewController
#define TriLength 1
– (void)viewDidLoad {
[super viewDidLoad];
[self setupScene];
[self createTetrahedron];
[self createCamera];
[self createLight];
}
– (void)setupScene {
SCNView *sv = [[SCNView alloc] initWithFrame:self.view.bounds];
sv.backgroundColor = [UIColor colorWithHue:0.25 saturation:0.2 brightness:1 alpha:1];
sv.scene = [SCNScene scene];
sv.allowsCameraControl = YES;
[self.view addSubview:sv];
self.sceneView = sv;
}
– (void)createTetrahedron {
SCNNode *o = [SCNNode node];
[self.sceneView.scene.rootNode addChildNode:o];
float dw = atan2f(sqrt(2.0) / 2.0, 1.0);
for (int i=0; i<4; i++) {
SCNNode *t = [self createTriangle];
if (i > 1) {
[t runAction:[SCNAction rotateByX:(i%2) ? dw : -dw y:0 z:0 duration:0.0]];
} else {
[t runAction:[SCNAction sequence:@[
[SCNAction rotateByX:0 y:M_PI * 0.5 z:0 duration:0],
[SCNAction rotateByX:0 y:0 z:M_PI duration:0],
[SCNAction moveByX:0 y:TriLength / sqrt(2.0) z:0 duration:0],
[SCNAction rotateByX:(i%2) ? dw : -dw y:0 z:0 duration:0.0]]]];
}
[o addChildNode:t];
}
[o runAction:[SCNAction rotateByX:(M_PI * 0.5 – dw) y:0 z:0 duration:0]];
self.current = o;
}
– (void)addTetrahedron {
SCNNode *o = [SCNNode node];
[self.sceneView.scene.rootNode addChildNode:o];
[o addChildNode:self.current];
int l = pow(2.0, self.count) * TriLength;
for (int i=0; i<3; i++) {
SCNNode *c = [self.current clone];
c.position =
(i == 0) ? SCNVector3Make(l * 0.5, -l * sin(M_PI/3.0), -l*0.29)
: (i == 1) ? SCNVector3Make(-l * 0.5, -l * sin(M_PI/3.0), -l * 0.29)
: SCNVector3Make(0, -l * sin(M_PI/3.0), l * 0.52);
[o addChildNode:c];
}
self.current = o;
self.count++;
}
– (SCNNode *)createTriangle {
float r = TriLength * 0.5;
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:CGPointMake(-r, 0)];
[path addLineToPoint:CGPointMake(0, r * sqrt(3.0))];
[path addLineToPoint:CGPointMake(r, 0)];
[path closePath];
SCNShape *triangle = [SCNShape shapeWithPath:path extrusionDepth:0.01];
SCNNode *triangleNode = [SCNNode nodeWithGeometry:triangle];
return triangleNode;
}
– (void)createCamera {
SCNNode *camera = [SCNNode node];
camera.camera = [SCNCamera camera];
camera.position = SCNVector3Make(0, –4, 10);
[self.sceneView.scene.rootNode addChildNode:camera];
}
– (void)createLight {
SCNLight *light = [SCNLight light];
light.type = SCNLightTypeOmni;
light.color = [UIColor colorWithHue:0.5 saturation:0.1 brightness:0.4 alpha:1];
SCNNode *lightNode = [SCNNode node];
lightNode.light = light;
lightNode.position = SCNVector3Make(0, 0, 40);
[self.sceneView.scene.rootNode addChildNode:lightNode];
}
– (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
if (self.count > 4) {
return;
}
[self addTetrahedron];
}
@end