Circle to Circle Vector Transform

Question

Hi

I have a program where you drag and drop circles on a scene using JavaFX. I don't want circles to collide to each other so I added a collision algorithm to check that, which now works. What puzzles me is what I want to do afterwards.

If two circles overlap I want to make a vector between the middle of the two and transform the moved circle in the direction of the vector until they no longer overlap.

            for (Stone stn:getCurrentScenario().getStones()) {
                if (stn.circle == circle) continue;

                double x1 = stn.circle.getTranslateX();
                double y1 = stn.circle.getTranslateY();
                double r1 = stn.circle.getRadius()+stn.circle.getStrokeWidth();

                double x2 = circle.getTranslateX();
                double y2 = circle.getTranslateY();
                double r2 = circle.getRadius();

                double distSq = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
                double radSumSq = (r1 + r2) * (r1 + r2);


                if (!(distSq != radSumSq && distSq > radSumSq)) {
                    System.out.println("Collision.");
                    // Transform "circle".

                }

            }

See also [*Ball to Ball Collision—Detection and Handling*](https://stackoverflow.com/q/345838/230513) — trashgod, Mar 22 '19 at 16:53

score 0 · Answer 1 · answered Mar 22 '19 at 20:50

I ended up skipping the vector idea and went by angle instead. Going to keep the title if someone else runs into a similar issue:

    double newX = circle.getTranslateX();
    double newY = circle.getTranslateY();


    for (Stone stn:getCurrentScenario().getStones()) {
        if (stn.circle == circle) continue;

        double x1 = stn.circle.getTranslateX();
        double y1 = stn.circle.getTranslateY();
        double r1 = stn.circle.getRadius()+stn.circle.getStrokeWidth();

        double x2 = newX;
        double y2 = newY;
        double r2 = circle.getRadius();

        double distSq = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
        double radSumSq = (r1 + r2) * (r1 + r2);


        if (!(distSq != radSumSq && distSq > radSumSq)) {
            double angle = Math.atan2(x1-x2,y1-y2);
            newX = x1 - Math.sin(angle) * (circle.getRadius() + circle.getStrokeWidth() + stn.circle.getRadius() + .01);
            newY = y1 - Math.cos(angle) * (circle.getRadius() + circle.getStrokeWidth() + stn.circle.getRadius() + .01);



        }
    }
    for (Stone stn:getCurrentScenario().getStones()) {
        if (stn.circle == circle) continue;
        double x1 = stn.circle.getTranslateX();
        double y1 = stn.circle.getTranslateY();
        double r1 = stn.circle.getRadius()+stn.circle.getStrokeWidth();

        double x2 = newX;
        double y2 = newY;
        double r2 = circle.getRadius();

        double distSq = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
        double radSumSq = (r1 + r2) * (r1 + r2);

        if (!(distSq != radSumSq && distSq > radSumSq)) {
            newX = oldX;
            newY = oldY;
            break;
        }
    }

    circle.setTranslateX(newX);
    circle.setTranslateY(newY);

I made that piece of code just to make sure that it works as intended. Going to improve it now.

Circle to Circle Vector Transform

1 Answers1