java - 检测直线与矩形的交点
问题描述
我想检测随机线与随机矩形的交点。我的 Line 类得到 4 个坐标并用它们制作一条线。我的intersectionWith 函数获取2 条线并返回交点,如果没有点,则返回null。
我有 2 个功能:一个找到最近的交点并返回它(我认为这无关紧要):位于 Line.java
public Point closestIntersectionToStartOfLine(Rectangle rect){
Line[] rectLines = new Line[4];
Point[] IntersectionPoints = new Point[4];
double minDistance=0;
//up
rectLines[0] = new Line(rect.getUpperLeft().getX(), rect.getUpperLeft().getY(), rect.getWidth()+rect.getUpperLeft().getX(), rect.getUpperLeft().getY());
//right
rectLines[1] = new Line(rect.getWidth()+rect.getUpperLeft().getX(), rect.getUpperLeft().getY(), rect.getUpperLeft().getX()+rect.getWidth(), rect.getHeight()+rect.getUpperLeft().getY());
//down
rectLines[2] = new Line(rect.getUpperLeft().getX()+rect.getWidth(), rect.getHeight()+rect.getUpperLeft().getY(), rect.getUpperLeft().getX(), rect.getUpperLeft().getY()+rect.getHeight());
//left
rectLines[3] = new Line(rect.getUpperLeft().getX(), rect.getUpperLeft().getY()+rect.getHeight(), rect.getUpperLeft().getX(), rect.getUpperLeft().getY());
for (int i=0; i<4; i++) {
if (intersectionWith(rectLines[i]) != null)
IntersectionPoints[i] = intersectionWith(rectLines[i]);
}
for (int i=0; i<IntersectionPoints.length; i++) {
if (i == 0)
minDistance = rect.getUpperLeft().distance(IntersectionPoints[i]);
else {
if (rect.getUpperLeft().distance(IntersectionPoints[i]) < minDistance)
Point.closestIntersectionToStartOfLine = IntersectionPoints[i];
}
}
return Point.closestIntersectionToStartOfLine;
}
这个函数将给定线的所有交点保存到一个列表中。位于 Rectangle.java
// Return a (possibly empty) List of intersection points
// with the specified line.
public java.util.List<Point> intersectionPoints(Line line) {
List<Point> intersectionPointsList = new ArrayList<Point>();
Line[] rectangleSides = new Line[4];
Point[] corners = new Point[4];
rectangleCorners(corners);
recatngleSides(rectangleSides, corners);
for (int i = 0; i < 4; i++) {
Point p = line.intersectionWith(rectangleSides[i]);
if (p != null && !intersectionPointsList.contains(p)) {
intersectionPointsList.add(p);
}
}
return intersectionPointsList;
}
public void rectangleCorners(Point[] corners) {
double width = this.getWidth();
double height = this.getHeight();
double x = this.upperLeft.getX();
double y = this.upperLeft.getY();
//upper left
corners[0] = this.getUpperLeft();
//upper right
corners[1] = new Point(x + width, y);
//down right
corners[2] = new Point(x + width, y + height);
//down left
corners[3] = new Point(x, y + height);
}
/**
* recatngleSides.
* Saves the lines in the 4 rectangle edges.
*
* @param sides - an empty array of lines
* @param corners - an array of edge points.
*/
public void recatngleSides(Line[] sides, Point[] corners) {
// up
sides[0] = new Line(corners[0], corners[1]);
// right
sides[1] = new Line(corners[1], corners[2]);
// down
sides[2] = new Line(corners[2], corners[3]);
// left
sides[3] = new Line(corners[3], corners[0]);
}
}
我不知道为什么,但它会将随机点识别为交点,如图所示。
解决方案
因为,如果你看看你的“随机”点在哪里,如果你将边延伸到无穷大,它们实际上就是非相交矩形的边所在的位置。您需要实际检查是否与作为矩形边的线段相交。
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