Skip to content

Instantly share code, notes, and snippets.

@yoshiki yoshiki/gist:7702066
Created Nov 29, 2013

Embed
What would you like to do?
2つの線の交点座標を求める関数。 線分が交わっていないとCGPointZeroが返る。 もし線分関係なしに延長線上に交点があるのかを求める場合は7〜10行目をコメントアウトすればよい。
+ (CGPoint)intersectionOfLineFrom:(CGPoint)p1 to:(CGPoint)p2 withLineFrom:(CGPoint)p3 to:(CGPoint)p4 {
CGFloat d = (p2.x - p1.x)*(p4.y - p3.y) - (p2.y - p1.y)*(p4.x - p3.x);
if (d == 0)
return CGPointZero; // parallel lines
CGFloat u = ((p3.x - p1.x)*(p4.y - p3.y) - (p3.y - p1.y)*(p4.x - p3.x))/d;
CGFloat v = ((p3.x - p1.x)*(p2.y - p1.y) - (p3.y - p1.y)*(p2.x - p1.x))/d;
if (u < 0.0 || u > 1.0)
return CGPointZero; // intersection point not between p1 and p2
if (v < 0.0 || v > 1.0)
return CGPointZero; // intersection point not between p3 and p4
CGPoint intersection;
intersection.x = p1.x + u * (p2.x - p1.x);
intersection.y = p1.y + u * (p2.y - p1.y);
return intersection;
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.