find diff color

ViewController.m

//
//  ViewController.m
//  FindDiffColor
//
//  Created by MizushimaYusuke on 9/8/15.
//  Copyright (c) 2015 MizushimaYusuke. All rights reserved.
//

#import "ViewController.h"
@import SceneKit;

@interface ViewController ()
@property (nonatomic, weak) SCNView *sceneView;
@property (nonatomic, weak) UISlider *levelSlider;
@property (nonatomic, strong) NSMutableArray *boxes;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self setupScene];
    [self createSlider];
    [self createColorCubes];
    [self createCamera];
}

- (void)setupScene {
    SCNView *sv = [[SCNView alloc] initWithFrame:self.view.bounds];
    sv.scene = [SCNScene scene];
    sv.allowsCameraControl = YES;
    sv.backgroundColor = [UIColor blackColor];
    [self.view addSubview:sv];
    self.sceneView = sv;
}

- (void)createColorCubes {
    
    float hue = (arc4random() % 10) * 0.1;
    float d = (self.levelSlider.maximumValue - self.levelSlider.value) * 0.3;
    UIColor *colorA = [UIColor colorWithHue:hue saturation:0.4 brightness:1 alpha:1];
    UIColor *colorB = [UIColor colorWithHue:hue saturation:0.39 + d brightness:1 alpha:1];

    self.boxes = [NSMutableArray array];
    
    int rand = arc4random() % 25;
    for (int i=0; i<25; i++) {
        float x = (i % 5) - 2;
        float y = (i / 5) - 2;
        SCNBox *box = [SCNBox boxWithWidth:0.8 height:0.8 length:0.8 chamferRadius:0.1];
        SCNNode *boxNode = [SCNNode nodeWithGeometry:box];
        
        if (i == rand) {
            box.firstMaterial.diffuse.contents = colorB;
            boxNode.name = @"diff";
        } else {
            box.firstMaterial.diffuse.contents = colorA;
        }
        boxNode.position = SCNVector3Make(x, y, 0);
        [self.sceneView.scene.rootNode addChildNode:boxNode];
        
        [self.boxes addObject:boxNode];
    }
}

- (void)createCamera {
    SCNNode *camera = [SCNNode node];
    camera.camera = [SCNCamera camera];
    camera.position = SCNVector3Make(0, 0, 8);
    [self.sceneView.scene.rootNode addChildNode:camera];
}

- (void)createSlider {
    UISlider *s = [[UISlider alloc] init];
    s.minimumValue = 1;
    s.maximumValue = 3;
    s.center = CGPointMake(CGRectGetMaxX(self.view.bounds) - 80, CGRectGetMaxY(self.view.bounds) - 100);
    [self.view addSubview:s];
    
    self.levelSlider = s;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    CGPoint p = [[touches anyObject] locationInView:self.sceneView];
    SCNHitTestResult *hit = [self.sceneView hitTest:p options:@{SCNHitTestSortResultsKey : @YES}].firstObject;
    if ([hit.node.name isEqual:@"diff"]) {
        [self.boxes enumerateObjectsUsingBlock:^(SCNNode *box, NSUInteger idx, BOOL *stop) {
            [box removeFromParentNode];
        }];


        [self createColorCubes];


    }
}

@end

http://lepetit-prince.net/ios/?p=4330