110 lines
3.9 KiB
Java
110 lines
3.9 KiB
Java
import codedraw.CodeDraw;
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/**
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* This class represents celestial bodies like stars, planets, asteroids, etc...
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*/
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public class Body {
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private double mass;
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private Vector3 massCenter; // position of the mass center.
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private Vector3 currentMovement;
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public Body(double mass, Vector3 massCenter, Vector3 currentMovement) {
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this.mass = mass;
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this.massCenter = massCenter;
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this.currentMovement = currentMovement;
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}
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/**
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* Returns the distance between the mass centers of this body and the specified body 'b'.
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*/
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public double distanceTo(Body b) {
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return massCenter.distanceTo(b.massCenter);
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}
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/**
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* Returns a vector representing the gravitational force exerted by 'b' on this body.
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* The gravitational Force F is calculated by F = G*(m1*m2)/(r*r), with m1 and m2 being the
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* masses of the objects interacting, r being the distance between the centers of the masses
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* and G being the gravitational constant.
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* Hint: see simulation loop in Simulation.java to find out how this is done.
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*/
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public Vector3 gravitationalForce(Body b) {
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Vector3 direction = b.massCenter.minus(massCenter);
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double distance = direction.length();
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direction.normalize();
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double force = Simulation.G * mass * b.mass / (distance * distance);
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return direction.times(force);
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}
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/**
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* Moves this body to a new position, according to the specified force vector 'force' exerted
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* on it, and updates the current movement accordingly.
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* (Movement depends on the mass of this body, its current movement and the exerted force.)
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* Hint: see simulation loop in Simulation.java to find out how this is done.
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*/
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public void move(Vector3 force) {
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// F = m*a -> a = F/m
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Vector3 newPosition = massCenter.plus(force.times(1.0 / mass)).plus(currentMovement);
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// new minus old position.
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Vector3 newMovement = newPosition.minus(massCenter);
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// update body state
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massCenter = newPosition;
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currentMovement = newMovement;
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}
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/**
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* Returns the approximate radius of this body.
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* (It is assumed that the radius r is related to the mass m of the body by r = m ^ 0.5,
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* where m and r measured in solar units.)
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*/
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public double radius() {
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return SpaceDraw.massToRadius(mass);
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}
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/**
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* Return the mass of the Body.
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*/
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public double mass() {
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return mass;
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}
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/**
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* Returns a new body that is formed by the collision of this body and 'b'. The impulse
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* of the returned body is the sum of the impulses of 'this' and 'b'.
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*/
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public Body merge(Body b) {
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double mass = this.mass + b.mass;
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return new Body(
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mass,
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massCenter.times(this.mass).plus(b.massCenter.times(b.mass)).times(1.0 / mass),
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currentMovement.times(this.mass).plus(b.currentMovement.times(b.mass)).times(1.0 / mass)
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);
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}
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/**
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* Draws the body to the specified canvas as a filled circle.
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* The radius of the circle corresponds to the radius of the body
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* (use a conversion of the real scale to the scale of the canvas as
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* in 'Simulation.java').
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* Hint: call the method 'drawAsFilledCircle' implemented in 'Vector3'.
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*/
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public void draw(CodeDraw cd) {
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cd.setColor(SpaceDraw.massToColor(mass));
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massCenter.drawAsFilledCircle(cd, SpaceDraw.massToRadius(mass));
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}
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/**
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* Returns a string with the information about this body including
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* mass, position (mass center) and current movement. Example:
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* "5.972E24 kg, position: [1.48E11,0.0,0.0] m, movement: [0.0,29290.0,0.0] m/s."
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*/
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public String toString() {
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return String.format(
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"%f kg, position: %s m, movement: %s m/s.",
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mass, massCenter.toString(), currentMovement.toString()
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);
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}
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}
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