java 两点之间的角度与 atan2
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Angle between 2 points with atan2
提问by vuvu
I was reading this postabout getting an angle between 2 points and was wondering. I thought atan2 is defined for atan2(y,x) here it is atan2(deltaX, deltaY), why is x first now?
我读这个职位有关获取2点之间的角度，想知道。我认为 atan2 是为 atan2(y,x) 定义的，这里是 atan2(deltaX, deltaY)，为什么现在先是 x？
public float getAngle(Point target) {
float angle = (float) Math.toDegrees(Math.atan2(target.x - x, target.y - y));
if (angle < 0) {
angle += 360;
}
return angle;
}
回答by Ruchira Gayan Ranaweera
Math.java it define as
Math.java 它定义为
public static double atan2(double y, double x) {
return StrictMath.atan2(y, x); // default impl. delegates to StrictMath
}
and this will return the counter-clock wise angle with respect to X- axis.
这将返回相对于 X 轴的逆时针角度。
If you interchange those two you will get the clock wise angle with respect to X- axis.
如果将这两个互换，您将获得相对于 X 轴的顺时针角度。
In Cartesian coordinate system we consider counter-clock wise angle with respect to X-axis. That is why Math.java use this as above.
在笛卡尔坐标系中，我们考虑相对于 X 轴的逆时针角度。这就是 Math.java 如上所述使用它的原因。
回答by Joni
Swapping the order of the arguments means that instead of the (counter-clockwise) angle with the X-axis you get the (clockwise) angle with the Y-axis. It's not wrong, just unusual.
交换参数的顺序意味着您得到的是与 Y 轴的（顺时针）角度，而不是与 X 轴的（逆时针）角度。这没有错，只是不寻常。
回答by aaa
Try this out:
试试这个：
// ... code
Target start = new Target();
start.setX(0);
start.setY(0);
Target aLine = new Target();
Target bLine = new Target();
aLine.setX(-65000);
aLine.setY(ress.getObstacle().getLine());
bLine.setX(65000);
bLine.setY(ress.getObstacle().getLine());
Line2D line = new Line2D.Float(aLine.getX(), aLine.getY(), bLine.getX(), bLine.getY());
List<Target> list = new ArrayList<Target>();
if (!(ress.getObstacle().getLine() == 0)) {
//check if points are there , if yes just reinitialize a linea-lineb and calculate the same in for:
String a = "";
try {
a = ress.getObstacle().getA().toStrin`enter code here`g();
} catch (NullPointerException e) {
}
if (!(a == "")) {
aLine.setX(ress.getObstacle().getA().getX());
aLine.setY(ress.getObstacle().getLine());
bLine.setX(ress.getObstacle().getB().getX());
bLine.setY(ress.getObstacle().getLine());
Line2D lineNew = new Line2D.Float(aLine.getX(), aLine.getY(), bLine.getX(), bLine.getY());
for (Target t : ress.getTargets()) {
Line2D line2 = new Line2D.Float(start.getX(), start.getY(), t.getX(), t.getY());
if (!line2.intersectsLine(lineNew)) {
list.add(t);
}
}
} else {
//-------------------start old part----------------------------------
for (Target t : ress.getTargets()) {
Line2D line2 = new Line2D.Float(start.getX(), start.getY(), t.getX(), t.getY());
if (!line2.intersectsLine(line)) {
list.add(t);
}
}
///////-------end old part
}
} else {
double angA = Math.toDegrees(StrictMath.atan2(ress.getObstacle().getA().getX() - start.getX(), ress.getObstacle().getA().getY() - start.getY()));
double angB = Math.toDegrees(StrictMath.atan2(ress.getObstacle().getB().getX() - start.getX(), ress.getObstacle().getB().getY() - start.getY()));
Boolean up = (ress.getObstacle().getA().getY()>0)&(ress.getObstacle().getB().getY()>0);
Boolean left = (ress.getObstacle().getA().getX()<0)&(ress.getObstacle().getB().getX()<0);
Boolean right = (ress.getObstacle().getA().getX()>0)&(ress.getObstacle().getB().getX()>0);
for (Target t : ress.getTargets()) {
double angT = Math.toDegrees(StrictMath.atan2(t.getX() - start.getX(), t.getY() - start.getY()));
if (up) {
if (!((angT > Math.min(angA,angB)) & (angT < Math.max(angB,angA))))
list.add(t);
} else
if (right || left) {
if ( !((angT > Math.min(angA,angB)) & (angT< Math.max(angB,angA)))) {
list.add(t);
}
} else
{
if ( ((angT > Math.min(angA,angB)) & (angT< Math.max(angB,angA)))) {
list.add(t);
}
}
}
}
sol.setTargets(list);
