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POFast Collision Detection for Circle Insertion into 2D Plane
 

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  1. POFast Collision Detection for Circle Insertion into 2D Plane
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    <p>I know there are lots of posts about collision detection generally for sprites moving about a 2D plane, but my question is slightly different.</p> <p>I'm inserting circles into a 2D plane. The circles have variable radii. I'm trying to optimize my method of finding a random position within the plane where I can insert a new circle without it colliding with any other circles already on the plane. Right now I'm using a very "un-optimized" approach that simply generates a random point within the plane and then checks it against all the other circles on the plane.</p> <p>Are there ways to optimize this? For this particular app, the bounds of the plane can only hold 20-25 circles at a time and typically there are between 5-10 present. As you would expect, when the number of circles approaches the max that can fit, you have to test many points before finding one that works. It gets very slow.</p> <p>Note: safeDistance is the radius of the circle I want to add to the plane.</p> <p>Here's the code:</p> <pre><code>- (CGPoint)getSafePosition:(float)safeDistance { // Point must be far enough from edges // Point must be far enough from other sprites CGPoint thePoint; BOOL pointIsSafe = NO; int sd = ceil(safeDistance); while(!pointIsSafe) { self.pointsTested++; // DEBUG // generate a random point inside the plane boundaries to test thePoint = CGPointMake((arc4random() % ((int)self.manager.gameView.frame.size.width - sd*2)) + sd, (arc4random() % ((int)self.manager.gameView.frame.size.height - sd*2)) + sd); if(self.manager.gameView.sprites.count &gt; 0) { for(BasicSprite *theSprite in self.manager.gameView.sprites) { // get distance between test point and the sprite position float distance = [BasicSprite distanceBetweenPoints:thePoint b:theSprite.position]; // check if distance is less than the sum of the min safe distances of the two entities if(distance &lt; (safeDistance + [theSprite minSafeDistance])) { // point not safe pointIsSafe = NO; break; } // if we get here, the point did not collide with the last tested point pointIsSafe = YES; } } else { pointIsSafe = YES; } } return thePoint; } </code></pre>
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    1. COYour question is not necceserily iphone related, I'm removing the iphone & objective-c tags so more ppl will join in
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    2. COA 2D plane is a line, which is of infinite length. So you would have infinite space for your circles, unless you added the restriction which states they have to exactly touch each other. Or did you mean a line segment as opposed to an infinite line?
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    3. CO@Mads: "A 2D plane is a line" -- what? Obviously, the OP is asking about a rectangular region of fixed, finite size in the plane. You know, like the screen on an iPhone, for example.
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