我可以检测到两条线的交点,但是如果我的线没有屏幕的长度,它将检测到该点不应该在的位置。
这里是预览:
因此,它不应检测到该相交,因为水平线没有那么长。
代码:
- (NSMutableArray *) intersectWithLines:(CGPoint)startPoint andEnd:(CGPoint)endPoint {
NSMutableArray *intersects = [[NSMutableArray alloc] init];
for(GameLine *line in [_lineBackground getLines]) {
double lineStartX = line.startPos.x;
double lineStartY = line.startPos.y;
double tempEndX = line.endPos.x;
double tempEndY = line.endPos.y;
double d = ((startPoint.x - endPoint.x)*(lineStartY - tempEndY)) - ((startPoint.y - endPoint.y) * (lineStartX - tempEndX));
if(d != 0) {
double sX = ((lineStartX - tempEndX) * (startPoint.x * endPoint.y - startPoint.y * endPoint.x) - (startPoint.x - endPoint.x) * (lineStartX * tempEndY - lineStartY * tempEndX)) / d;
double sY = ((lineStartY - tempEndY) * (startPoint.x * endPoint.y - startPoint.y * endPoint.x) - (startPoint.y - endPoint.y) * (lineStartX * tempEndY - lineStartY * tempEndX)) / d;
if([self isValidCGPoint:CGPointMake(sX, sY)]) {
[intersects addObject:[NSValue valueWithCGPoint:CGPointMake(sX, sY)]];
}
}
}
return intersects;
}
最佳答案
如果我正确理解了您的问题,则需要确定两个线段的交点。这应该与以下方法一起使用:
- (NSValue *)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 nil; // 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 nil; // intersection point not between p1 and p2
if (v < 0.0 || v > 1.0)
return nil; // 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 [NSValue valueWithCGPoint:intersection];
}