Question

I’m making a space game, and I’d like to make a small drone ship orbit my bigger player ship. I’m not entirely sure how to make it orbit in a perfect circle. So far I can make it move in a diamond shape, but my attempts to correct for the circle shape have ended in failure.

Basically, I’m doing something like this:

float centerX = ship.getX() + (ship.getWidth() / 2);
float centerY = ship.getY() + (ship.getHeight() / 2);
float droneX = drone.getX();
float droneY = drone.getY();
float radius = drone.getRadius();
float xDiff = Math.abs(droneX - centerX);
float yDiff = Math.abs(droneY - centerY);
float moveByX = Math.abs(radius / (xDiff == 0 ? 1 : xDiff) / smoother);
float moveByY = Math.abs(radius / (yDiff == 0 ? 1 : yDiff) / smoother);

And then I move the drone by the moveByX and moveByY values. It works fine in a diamond shape, as I mentioned, but how can I improve this to calculate the correct circular pattern?

Answer 1

Okay, since you’re using x and y differences, it will only go in a straight line, which explains the diamond pattern. In order to get the circle, you’ll have to break out trigonometry.

float angle; //angle in radians
float droneX = drone.getRadius() * Math.sin(angle); 
float droneY = drone.getRadius() * Math.cos(angle);

After that you can use your movement code. And angle should probably be kept on the drone, and in radians.