Question

我看过"Third Eye Crime"的预告片。

如何实现视锥的蓝色视野，使其形状根据障碍物而变化？

enter image description here

我的尝试是投射光线直到出现障碍物，然后我用光线的终点绘制圆锥形状。

enter image description here

我的方法的问题是锥体的精度取决于光线的数量。除了投射的光线越多，性能越差。

在这里你可以看到光线：

enter image description here

在这里，您可以看到使用光线的终点绘制的圆锥形状：

enter image description here

有更好的解决方案吗？

Answer 1

你的问题一直困扰着我，但我无法找到一个完全有效的答案。我的工作笔记对我来说太多了，不能把它写成评论，所以我把它作为答案添加。

我的第一个问题是测试视野线和任何障碍物之间的接触。不幸的是，SpriteKit只有contactBitMask，它可以完成这项工作并提供接触坐标。

我查看了SKNode的intersectsNode:，但它的返回值只是一个BOOL，我们需要坐标。

我还查看了Apple的Sprite Kit编程指南的Searching for Physics Bodies部分。这涉及视线，障碍物等......这里使用的命令是bodyAlongRayStart:end:。返回是它与之相交的第一个物理体，但没有提供实际接触点的坐标。

我最终得到的代码首先描绘了完整的视线锥。接下来，找到与对象联系的所有行都使用contact.contactPoint获得了联系点，然后删除了违规行。到现在为止还挺好。但是我试图将删除的线绘制到新的终点（接触点）时遇到了麻烦。由于一些莫名其妙的原因，只有一些被删除的行被重绘而不是全部。

请记住这是粗糙的代码所以拍打它，拉它并将它扔到墙上几次。例如，你并不需要数组。我希望这会引导你朝着正确的方向前进，或者你可以发现一些我无法看到的东西。

旁注：我在模拟器iPhone（4英寸）版本中运行它。

#import "MyScene.h"

typedef NS_OPTIONS(uint32_t, CNPhysicsCategory)
{
    Category1  = 1 << 0,
    Category2  = 1 << 1,
    Category3  = 1 << 2,
};

@interface MyScene()<SKPhysicsContactDelegate>
@end

@implementation MyScene
{
    SKSpriteNode *player;
    SKSpriteNode *obstacle1;
    SKSpriteNode *obstacle2;
    SKSpriteNode *obstacle3;
    SKSpriteNode *obstacle4;

    NSMutableArray *beamArray;

    int beamCounter;
}

-(id)initWithSize:(CGSize)size
{
    if (self = [super initWithSize:size])
    {
        self.physicsWorld.contactDelegate = self;

        beamArray = [[NSMutableArray alloc] init];

        beamCounter = 0;

         player = [SKSpriteNode spriteNodeWithColor:[SKColor redColor] size:CGSizeMake(20, 20)];
        player.position = CGPointMake(100, 150);
        [self addChild:player];

        obstacle1 = [SKSpriteNode spriteNodeWithColor:[SKColor blueColor] size:CGSizeMake(200, 20)];
        obstacle1.name = @"obstacle1";
        obstacle1.position = CGPointMake(250, 100);
        obstacle1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:obstacle1.size];
        obstacle1.physicsBody.affectedByGravity = NO;
        obstacle1.physicsBody.categoryBitMask = Category2;
        obstacle1.physicsBody.collisionBitMask = 0x00000000;
        [self addChild:obstacle1];

        obstacle2 = [SKSpriteNode spriteNodeWithColor:[SKColor blueColor] size:CGSizeMake(40, 40)];
        obstacle2.name = @"obstacle2";
        obstacle2.position = CGPointMake(400, 200);
        obstacle2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:obstacle2.size];
        obstacle2.physicsBody.affectedByGravity = NO;
        obstacle2.physicsBody.categoryBitMask = Category2;
        obstacle2.physicsBody.collisionBitMask = 0x00000000;
        [self addChild:obstacle2];

        obstacle3 = [SKSpriteNode spriteNodeWithColor:[SKColor blueColor] size:CGSizeMake(50, 20)];
        obstacle3.name = @"obstacle3";
        obstacle3.position = CGPointMake(530, 130);
        obstacle3.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:obstacle3.size];
        obstacle3.physicsBody.affectedByGravity = NO;
        obstacle3.physicsBody.categoryBitMask = Category2;
        obstacle3.physicsBody.collisionBitMask = 0x00000000;
        [self addChild:obstacle3];

        for (int y = 0; y <= 320; y++)
        {
            SKShapeNode *beam1 = [SKShapeNode node];
            beam1.name = [NSString stringWithFormat:@"%i",beamCounter++];
            CGMutablePathRef pathToDraw = CGPathCreateMutable();
            CGPathMoveToPoint(pathToDraw, NULL, player.position.x, player.position.y);
            CGPathAddLineToPoint(pathToDraw, NULL, 600, y);
            beam1.path = pathToDraw;
            [beam1 setStrokeColor:[UIColor yellowColor]];
            [beam1 setLineWidth:2.0];

            beam1.physicsBody = [SKPhysicsBody bodyWithEdgeFromPoint:CGPointMake(player.position.x, player.position.y) toPoint:CGPointMake(600, y)];
            beam1.physicsBody.affectedByGravity = NO;
            beam1.physicsBody.categoryBitMask = Category1;
            beam1.physicsBody.contactTestBitMask = Category2;

            [self addChild:beam1];

            [beamArray addObject:beam1];
        }
    }
    return self;
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //
}

-(void)update:(CFTimeInterval)currentTime
{
    //
}

- (void)didBeginContact:(SKPhysicsContact *)contact
{
    NSLog(@"bodyA:%@ bodyB:%@",contact.bodyA.node.name, contact.bodyB.node.name);

     uint32_t collision = (contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask);

    if (collision == (Category1 | Category2))
    {
        CGPoint newEndPoint = contact.contactPoint;

        [beamArray removeObject:contact.bodyA.node.name];
        [contact.bodyA.node removeFromParent];

        SKShapeNode *beam1 = [SKShapeNode node];
        beam1.name = [NSString stringWithFormat:@"%i",beamCounter++];
        CGMutablePathRef pathToDraw = CGPathCreateMutable();
        CGPathMoveToPoint(pathToDraw, NULL, player.position.x, player.position.y);
        CGPathAddLineToPoint(pathToDraw, NULL, newEndPoint.x, newEndPoint.y);
        beam1.path = pathToDraw;
        [beam1 setStrokeColor:[UIColor greenColor]];
        [beam1 setLineWidth:2.0];

        [self addChild:beam1];

    }
}

@end

删除触摸线：

enter image description here