In LibGDX, how might I make an object orbit around a position?

Question

I need an object, which would be a circle, made with ShaderRender, to orbit around a specified point. In LibGDX is there a method or something that would allow me to accomplish this? If not, could you please provide a code example?

Answer 1

If you wish for an object to orbit around a specified point in two dimensional space, you want to use some trigonometric functions. Here is an example method to calculate an objects position in an orbit:

class OrbitUtilities {
   /* currentOrbitDegrees: the degrees around the orbit that the satellite is(can greater that 360(361 would be equivalent to 1))
    * distanceFromCenterPoint: the distance in world units from the center point that the satellite is
    * centerPoint: the vector of the center point of the orbit system
    */
    public Vector2 calculateOrbit(float currentOrbitDegrees, float distanceFromCenterPoint, Vector2 centerPoint) {
        float radians = Math.toRadians(currentOrbitDegrees);

        float x = (Math.cos(radians) * distanceFromCenterPoint) + centerPoint.x;
        float y = (Math.sin(radians) * distanceFromCenterPoint) + centerPoint.y;

        return new Vector2(x, y);
    }
}

Answer 2

you need to keep the angle of the object (alpha) , declare float alpha =0, then in render method do something like this

x = Math.cos(alpha*MathUtils.DegreesToRadians)* distance;
y = Math.sin(alpha* MathUtils.DegreesToRadians )* distance; 
alpha++;
sprite.setPosition(x,y);