Rounding Inaccuracies When Combining Areas in Java?

Question

I\'m working with Areas in Java.

My test program draws three random triangles and combines them to form one or more polygons. After the Areas

Answer 1

I played around with this, and found a hacky way of getting rid of these. I'm not 100% sure that this will work in all cases, but it might.

After reading that the Area.transform's JavaDoc mentions

Transforms the geometry of this Area using the specified AffineTransform. The geometry is transformed in place, which permanently changes the enclosed area defined by this object.

I had a hunch and added possibility of rotating the Area by holding down a key. As the Area was rotating, the "inward" edges started to slowly disappear, until only the outline was left. I suspect that the "inward" edges are actually two edges very close to each other (so they look like a single edge), and that rotating the Area causes very small rounding inaccuracies, so the rotating sort of "melts" them together.

I then added a code to rotate the Area in very small steps for a full circle on keypress, and it looks like the artifacts disappear:

The image on the left is the Area built from 10 different random triangles (I upped the amount of triangles to get "failing" Areas more often), and the one on the right is the same Area, after being rotated full 360 degrees in very small increments (10000 steps).

Here's the piece of code for rotating the area in small steps (smaller amounts than 10000 steps would probably work just fine for most cases):

        final int STEPS = 10000; //Number of steps in a full 360 degree rotation
        double theta = (2*Math.PI) / STEPS; //Single step "size" in radians

        Rectangle bounds = area.getBounds();    //Getting the bounds to find the center of the Area
        AffineTransform trans = AffineTransform.getRotateInstance(theta, bounds.getCenterX(), bounds.getCenterY()); //Transformation matrix for theta radians around the center

        //Rotate a full 360 degrees in small steps
        for(int i = 0; i < STEPS; i++)
        {
            area.transform(trans);
        }

As I said before, I'm not sure if this works in all cases, and the amount of steps needed might be much smaller or larger depending on the scenario. YMMV.