Flocking separation rule

Question

-(CGPoint)Rule2:(Boid*)b
    {
        CGPoint v = CGPointMake(0, 0);

        for (Boid *boid in ActiveBoids)
        {
            if (boid != b)
            {
                NSLog(@"%f", [Utilities Magnitude:boid.position] - [Utilities Magnitude:b.position]);
                if(([Utilities Magnitude:boid.position] - [Utilities Magnitude:b.position]) < 150)
                {
                    v = [Utilities MinusVector:v Vector2:CGPointMake(boid.position.x - b.position.x, boid.position.y - b.position.y)];
                    NSLog(@"%f", v.x);
                    NSLog(@"%f", v.y);
                }
            }
        }
        return v;
    }

My magnitude and subtract methods both work fine:

+ (CGPoint)MinusVector:(CGPoint)v1 Vector2:(CGPoint)v2
{
    return CGPointMake(v1.x - v2.x, v1.y - v2.y);
}

+ (float)Magnitude:(CGPoint)p1
{
    return hypot(p1.x, p1.y);
}

For some reason this is my output from that method:

Error Log

I've been looking at this for too long to see what's wrong. Any ideas?

You might check out Apple's SpriteKit implementation of boids flocking behavior from WWDC 2014. Some details here: https://stackoverflow.com/q/44235801/4376309 — peacetype, Jul 12 '17 at 08:00

score 0 · Accepted Answer · answered Mar 07 '14 at 04:12

0

It looks like your condition is incorrect. You're taking the difference of the magnitudes, but you want the magnitude of the difference. I think you want this:

if ([Utilities Magnitude:CGPointMake (boid.position - b.position)] < 150)

etc.

answered Mar 07 '14 at 04:12

user1118321

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Flocking separation rule

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