[英]Java: Rotate triangle around mass center
Im creating method that should rotate triangle around it's mass center, it should work, but my check shows that it doesn't. 我创建的方法应该围绕它的重心旋转三角形,它应该可以,但是我的检查显示它没有。 I understand that it might be not precise rotation, but still point that is mass center should remains the same after rotation of triangle.
我知道这可能不是精确的旋转,但是仍然要注意的是,在旋转了三角形之后,质心仍应保持不变。
What I did wrong? 我做错了什么?
public void rotateAroundMassCenter(double grad){
System.out.println("Starting...");
Point initial = this.massCenter();
Point o =this.massCenter();
o.printPoint();
double angle=Math.toRadians(grad);
System.out.println();
//formulas
// x' = x0+(x-x0)*cos(A)+(y0-y)*sin(alpha);
// y' = y0+(x-x0)*sin(A)+(y-y0)*cos(alpha);
//new points
int ax = (int) (o.x+(this.getA().x-o.x)*Math.cos(angle)-(this.getA().y-o.y) *Math.sin(angle));
int ay = (int) (o.y+(this.getA().x-o.x)*Math.sin(angle)+(this.getA().y-o.y) * Math.cos(angle));
this.a.movePoint(ax, ay);
int bx = (int) (o.x+(this.getB().x-o.x)*Math.cos(angle)-(this.getB().y-o.y) *Math.sin(angle));
int by = (int) (o.y+(this.getB().x-o.x)*Math.sin(angle)+(this.getB().y-o.y) * Math.cos(angle));
this.b.movePoint(bx, by);
int cx = (int) (o.x+(this.getC().x-o.x)*Math.cos(angle)-(this.getC().y-o.y) *Math.sin(angle));
int cy = (int) (o.y+(this.getC().x-o.x)*Math.sin(angle)+(this.getC().y-o.y) * Math.cos(angle));
this.c.movePoint(cx, cy);
Point finalCenter=this.massCenter();
System.out.println();
finalCenter.printPoint();
//check center position after rotate
if (initial==finalCenter ){
System.out.println("Rotation was correct");
}
else{
System.out.println("Algorytm is wrong");
}
this.print();
}
here how i find mass center: 在这里我如何找到大众中心:
// mass centre
public Point massCenter(){
double x = (this.getA().x+this.getB().x+this.getC().x)/3;
double y = (this.getA().y+this.getB().y+this.getC().y)/3;
Point o= new Point(x,y);
return o;
}
Result: 结果:
Ready to go
Triangle is:
A:(1.0; 1.0)B: (3.0; 1.0)C: (1.0; 4.0)
Starting...
(1.6666666666666667;2.0)Old center
New center
(3.0;3.3333333333333335)Algorithm is wrong
Triangle is:
A:(2.0; 1.0)B: (6.0; 3.0)C: (1.0; 6.0)
very little mistake ^^ 很小的错误^^
if (initial==finalCenter ){...
that's never true, you must compare by using equal: 永远都不是,您必须使用等于进行比较:
if (initial.equals(finalCenter) ){...
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