java - Polygon moves while being rotated -


i'm doing couple of tests polygons (rotating them) , i've run annoying issue crops while i'm rotating them. issue is, polygons seem moving when rotate, , fly out of screen. i've been using affinetransform rotate them, , haven't been translating them shouldn't moving, right? here's code:

import java.awt.*; import java.awt.geom.affinetransform; import java.awt.geom.point2d;  public class physicsprop {     point2d[] originalpoints;     point2d[] newpoints = originalpoints;      int x;     int y;      double rotation = 0.0;      public physicsprop(point2d[] points){         originalpoints = points;         newpoints = points;     }      public polygon pointstopoly(point2d[] points){         polygon p = new polygon();         (int = 0; < points.length; i++){             p.addpoint((int) points[i].getx(), (int) points[i].gety());         }         return p;     }      public void rotatemodel(double theta){         affinetransform.getrotateinstance(math.todegrees(theta), pointstopoly(newpoints).getbounds().getcenterx(), pointstopoly(newpoints).getbounds().getcentery()).transform(originalpoints, 0, newpoints, 0, originalpoints.length);     }      public polygon getmodel(){         return pointstopoly(newpoints);     }      public void setmodel(point[] points){         originalpoints = points;     }      public rectangle getbounds(){         return pointstopoly(newpoints).getbounds();     } }

i'd know what's going wrong code, , if there's better way around i'm trying achieve (rotating polygons). here's render , rotate polygons:

g2.setcolor(color.pink);             (physicsprop p : currentlevel.physicsobjects){                 g2.drawpolygon(p.pointstopoly(p.newpoints));                 p.rotatemodel(0.001);             }

thanks help!

try caching centerpoint of polygon, , using cached point point around rotate. nothing guarantees you'll calculate same exact x/y center point arbitrary polygon in arbitrary rotation, remove risk (and cpu cycles) , cache once , reuse there.


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