objective-c判断两条线段相交
参考自：http://zhidao.baidu.com/question/146717333
| // // LineIntersect.h // HungryBear // // Created by Bruce Yang on 12-3-12. // Copyright (c) 2012年EricGameStudio. All rights reserved. // #import<cstdio> #import"Box2D.h" #define zero(x) (((x)>0?(x):-(x))<b2_epsilon) @interfaceLineIntersect : NSObject #pragma mark- #pragma mark适用于b2Vec2的版本~ //判两线段相交,包括端点和部分重合 +(int) intersect_in:(b2Vec2)u1 u2:(b2Vec2)u2 v1:(b2Vec2)v1 v2:(b2Vec2)v2; //计算两线段交点,请判线段是否相交(同时还是要判断是否平行!) +(b2Vec2) intersection:(b2Vec2)u1 u2:(b2Vec2)u2 v1:(b2Vec2)v1 v2:(b2Vec2)v2; #pragma mark- #pragma mark适用于CGPoint的版本~ +(int) intersect_in2:(CGPoint)u1 u2:(CGPoint)u2 v1:(CGPoint)v1 v2:(CGPoint)v2; //计算两线段交点,请判线段是否相交(同时还是要判断是否平行!) +(CGPoint) intersection2:(CGPoint)u1 u2:(CGPoint)u2 v1:(CGPoint)v1 v2:(CGPoint)v2; #pragma mark- #pragma mark验证上述几个方法的移植是否存在什么问题~ +(void) validateAlgorithm; @end // // LineIntersect.mm // HungryBear // // Created by Bruce Yang on 12-3-12. // Copyright (c) 2012年EricGameStudio. All rights reserved. // #import"LineIntersect.h" @implementationLineIntersect //计算交叉乘积(P1-P0)x(P2-P0) +(double) xmult:(b2Vec2)p1 p2:(b2Vec2)p2 p3:(b2Vec2)p0 { return(p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y); } //判点是否在线段上,包括端点 +(int) dot_online_in:(b2Vec2)p l1:(b2Vec2)l1 l2:(b2Vec2)l2 { returnzero([selfxmult:p p2:l1 p3:l2]) && (l1.x-p.x)*(l2.x-p.x) < b2_epsilon && (l1.y-p.y)*(l2.y-p.y) < b2_epsilon; } //判两点在线段同侧,点在线段上返回0 +(int) same_side:(b2Vec2)p1 p2:(b2Vec2)p2 l1:(b2Vec2)l1 l2:(b2Vec2)l2 { return[selfxmult:l1 p2:p1 p3:l2] * [selfxmult:l1 p2:p2 p3:l2] > b2_epsilon; } //判两直线平行 +(int) parallel:(b2Vec2)u1 u2:(b2Vec2)u2 v1:(b2Vec2)v1 v2:(b2Vec2)v2 { returnzero((u1.x-u2.x)*(v1.y-v2.y)-(v1.x-v2.x)*(u1.y-u2.y)); } //判三点共线 +(int) dots_inline:(b2Vec2)p1 p2:(b2Vec2)p2 p3:(b2Vec2)p3 { returnzero([selfxmult:p1 p2:p2 p3:p3]); } //判两线段相交,包括端点和部分重合 +(int) intersect_in:(b2Vec2)u1 u2:(b2Vec2)u2 v1:(b2Vec2)v1 v2:(b2Vec2)v2 { if(![selfdots_inline:u1 p2:u2 p3:v1] || ![selfdots_inline:u1 p2:u2 p3:v2]) { return![selfsame_side:u1 p2:u2 l1:v1 l2:v2] && ![selfsame_side:v1 p2:v2 l1:u1 l2:u2]; }else{ return[selfdot_online_in:u1 l1:v1 l2:v2] || [selfdot_online_in:u2 l1:v1 l2:v2] || [selfdot_online_in:v1 l1:u1 l2:u2] || [selfdot_online_in:v2 l1:u1 l2:u2]; } } //计算两线段交点,请判线段是否相交(同时还是要判断是否平行!) +(b2Vec2) intersection:(b2Vec2)u1 u2:(b2Vec2)u2 v1:(b2Vec2)v1 v2:(b2Vec2)v2 { b2Vec2 ret=u1; doublet=((u1.x-v1.x)*(v1.y-v2.y)-(u1.y-v1.y)*(v1.x-v2.x)) /((u1.x-u2.x)*(v1.y-v2.y)-(u1.y-u2.y)*(v1.x-v2.x)); ret.x+=(u2.x-u1.x)*t; ret.y+=(u2.y-u1.y)*t; returnret; } #pragma mark- #pragma mark适用于CGPoint的版本~ //计算交叉乘积(P1-P0)x(P2-P0) +(double) xmult2:(CGPoint)p1 p2:(CGPoint)p2 p3:(CGPoint)p0 { return(p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y); } //判点是否在线段上,包括端点 +(int) dot_online_in2:(CGPoint)p l1:(CGPoint)l1 l2:(CGPoint)l2 { returnzero([selfxmult2:p p2:l1 p3:l2]) && (l1.x-p.x)*(l2.x-p.x) < b2_epsilon && (l1.y-p.y)*(l2.y-p.y) < b2_epsilon; } //判两点在线段同侧,点在线段上返回0 +(int) same_side2:(CGPoint)p1 p2:(CGPoint)p2 l1:(CGPoint)l1 l2:(CGPoint)l2 { return[selfxmult2:l1 p2:p1 p3:l2] * [selfxmult2:l1 p2:p2 p3:l2] > b2_epsilon; } //判两直线平行 +(int) parallel2:(CGPoint)u1 u2:(CGPoint)u2 v1:(CGPoint)v1 v2:(CGPoint)v2 { returnzero((u1.x-u2.x)*(v1.y-v2.y)-(v1.x-v2.x)*(u1.y-u2.y)); } //判三点共线 +(int) dots_inline2:(CGPoint)p1 p2:(CGPoint)p2 p3:(CGPoint)p3 { returnzero([selfxmult2:p1 p2:p2 p3:p3]); } +(int) intersect_in2:(CGPoint)u1 u2:(CGPoint)u2 v1:(CGPoint)v1 v2:(CGPoint)v2 { if(![selfdots_inline2:u1 p2:u2 p3:v1] || ![selfdots_inline2:u1 p2:u2 p3:v2]) { return![selfsame_side2:u1 p2:u2 l1:v1 l2:v2] && ![selfsame_side2:v1 p2:v2 l1:u1 l2:u2]; }else{ return[selfdot_online_in2:u1 l1:v1 l2:v2] || [selfdot_online_in2:u2 l1:v1 l2:v2] || [selfdot_online_in2:v1 l1:u1 l2:u2] || [selfdot_online_in2:v2 l1:u1 l2:u2]; } } //计算两线段交点,请判线段是否相交(同时还是要判断是否平行!) +(CGPoint) intersection2:(CGPoint)u1 u2:(CGPoint)u2 v1:(CGPoint)v1 v2:(CGPoint)v2 { CGPoint ret=u1; doublet=((u1.x-v1.x)*(v1.y-v2.y)-(u1.y-v1.y)*(v1.x-v2.x)) /((u1.x-u2.x)*(v1.y-v2.y)-(u1.y-u2.y)*(v1.x-v2.x)); ret.x+=(u2.x-u1.x)*t; ret.y+=(u2.y-u1.y)*t; returnret; } #pragma mark- #pragma mark验证上述几个方法的移植是否存在什么问题~ +(void) validateIntersect:(b2Vec2)u1 u2:(b2Vec2)u2 v1:(b2Vec2)v1 v2:(b2Vec2)v2 { b2Vec2 answer; if([selfparallel:u1 u2:u2 v1:v1 v2:v2] || ![selfintersect_in:u1 u2:u2 v1:v1 v2:v2]){ printf("无交点!\n"); }else{ answer = [selfintersection:u1 u2:u2 v1:v1 v2:v2]; printf("交点为:(%lf,%lf)\n", answer.x, answer.y); } } +(void) validateAlgorithm { [LineIntersect validateIntersect:b2Vec2(0,1) u2:b2Vec2(1,0) v1:b2Vec2(0,0) v2:b2Vec2(1,1)]; [LineIntersect validateIntersect:b2Vec2(0,10) u2:b2Vec2(10,0) v1:b2Vec2(0,0) v2:b2Vec2(10,10)]; [LineIntersect validateIntersect:b2Vec2(-2,0) u2:b2Vec2(2,0) v1:b2Vec2(-1,3) v2:b2Vec2(-1, -1)]; [LineIntersect validateIntersect:b2Vec2(-2,0) u2:b2Vec2(2,0) v1:b2Vec2(-1,3) v2:b2Vec2(1, -2)]; } @end |