fi.utu.cs.physics
Class Body

java.lang.Object
  |
  +--fi.utu.cs.physics.Body

Direct Known Subclasses:

Asteroid, MomentaryBody, Ship

public abstract class Body

extends java.lang.Object

A moving physical body with mass and dimensionality. The outline of the body is approximated with a bounding circle of a given radius, which is used in detecting overlaps. The body can be owned by an instance of the class Universe, which may set boundaries to the position. The body can be either corporeal or ethereal, which determines whether it can collide or not (i.e., only the corporeal bodies can collide).

See Also:

Universe

Constructor Summary

protected	Body(double m, double r) Constructs a body with the mass m and the radius r.
protected	Body(double m, double r, Point2 p) Constructs a body with the mass m, the radius r and the position p.
protected	Body(double m, double r, Point2 p, Vector2 v) Constructs a body with the mass m, the radius r, the position p and the velocity v.
protected	Body(double m, double r, Point2 p, Vector2 v, Vector2 a) Constructs a body with the mass m, the radius r, the position p, the velocity v and the acceleration a.

Method Summary

void	advance(double dt) Advances the time dt seconds and updates the position and velocity of the body accordingly.
void	elasticCollision(Body other) Realizes an elastic collision for both the body and the body other.
Vector2	getAcceleration() Returns the acceleration of the body.
double	getMass() Returns the mass of the body.
Universe	getOwner() Returns the owner of the body or null if the body has no owner.
Point2	getPosition() Returns the position of the body.
double	getRadius() Returns the radius of the bounding circle.
Vector2	getVelocity() Returns the velocity of the body.
boolean	isColliding(Body other) Returns whether the body collides with the body other.
boolean	isCorporeal() Returns true if the body is corporeal or false if the body is ethereal.
boolean	isOverlapping(Body other) Checks whether the body overlaps the body other.
void	setAcceleration(double ax, double ay) Sets the acceleration of the body.
void	setAcceleration(Vector2 a) Sets the acceleration of the body to a.
void	setCorporeal() Sets the body to be corporeal.
void	setEthereal() Sets the body to be ethereal.
void	setMass(double m) Sets the mass of the body to m.
void	setOwner(Universe u) Sets the universe that owns the body to u.
void	setPosition(double x, double y) Sets the position of the body.
void	setPosition(Point2 p) Sets the position of the body to p.
void	setRadius(double r) Sets the radius of the bounding circle to r.
void	setVelocity(double vx, double vy) Sets the velocity of the body.
void	setVelocity(Vector2 v) Sets the velocity of the body to v.
java.lang.String	toString() Returns a string that contains the values of the attributes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Body

protected Body(double m,
               double r)

Constructs a body with the mass m and the radius r. The body resides in the origin and has a zero velocity and a zero acceleration. The body is corporeal and has no owner.

Body

protected Body(double m,
               double r,
               Point2 p)

Constructs a body with the mass m, the radius r and the position p. The body has a zero velocity and a zero acceleration. The body is corporeal and has no owner.

Body

protected Body(double m,
               double r,
               Point2 p,
               Vector2 v)

Constructs a body with the mass m, the radius r, the position p and the velocity v. The body has a zero acceleration. The body is corporeal and has no owner.

Body

protected Body(double m,
               double r,
               Point2 p,
               Vector2 v,
               Vector2 a)

Constructs a body with the mass m, the radius r, the position p, the velocity v and the acceleration a. The body is corporeal and has no owner.

Method Detail

getMass

public double getMass()

Returns the mass of the body.

getRadius

public double getRadius()

Returns the radius of the bounding circle.

getPosition

public Point2 getPosition()

Returns the position of the body.

getVelocity

public Vector2 getVelocity()

Returns the velocity of the body.

getAcceleration

public Vector2 getAcceleration()

Returns the acceleration of the body.

setMass

public void setMass(double m)

Sets the mass of the body to m.

setRadius

public void setRadius(double r)

Sets the radius of the bounding circle to r.

setPosition

public void setPosition(double x,
                        double y)

Sets the position of the body.

Parameters:

x - The x coordinate of the position.

y - The y coordinate of the position.

See Also:

setPosition(Point2)

setPosition

public void setPosition(Point2 p)

Sets the position of the body to p.

setVelocity

public void setVelocity(double vx,
                        double vy)

Sets the velocity of the body.

Parameters:

vx - The horizontal velocity.

vy - The vertical velocity.

See Also:

setVelocity(Vector2)

setVelocity

public void setVelocity(Vector2 v)

Sets the velocity of the body to v.

setAcceleration

public void setAcceleration(double ax,
                            double ay)

Sets the acceleration of the body.

Parameters:

ax - The horizontal acceleration.

ay - The vertical acceleration.

See Also:

setAcceleration(Vector2)

setAcceleration

public void setAcceleration(Vector2 a)

Sets the acceleration of the body to a.

getOwner

public Universe getOwner()

Returns the owner of the body or null if the body has no owner.

setOwner

public void setOwner(Universe u)

Sets the universe that owns the body to u.

isCorporeal

public boolean isCorporeal()

Returns true if the body is corporeal or false if the body is ethereal.

setCorporeal

public void setCorporeal()

Sets the body to be corporeal.

See Also:

isColliding(Body)

setEthereal

public void setEthereal()

Sets the body to be ethereal.

See Also:

isColliding(Body)

advance

public void advance(double dt)

Advances the time dt seconds and updates the position and velocity of the body accordingly. The new horizontal position x' is calculated from the equation x' = ½a_xt² + v_xt + x, and the vertical position is calculated accordingly. The new horizontal velocity v_x' is calculated from the equation v_x' = a_xt + v_x, and the vertical velocity is calculated accordingly.

isOverlapping

public boolean isOverlapping(Body other)

Checks whether the body overlaps the body other. An overlap occurs if the distance between the centers of the bodies is smaller than the sum of the respective radii.

See Also:

isColliding(Body)

isColliding

public boolean isColliding(Body other)

Returns whether the body collides with the body other. A collision occurs when the bodies overlap each other for the first time (i.e., at the moment of impact) and both bodies are corporeal.

See Also:

isOverlapping(Body), isCorporeal()

elasticCollision

public void elasticCollision(Body other)

Realizes an elastic collision for both the body and the body other. The linear momentum and kinetic energy of the bodies is conserved in the collision. The new velocity v₁' is calculated from the equation v₁' = v₁ (m₁ - m₂) / (m₁ + m₂) + v₂ 2m₂ / (m₁ + m₂) and v₂' from the equation v₂' = v₁ 2m₁ / (m₁ + m₂) + v₂ (m₂ - m₁) / (m₂ + m₁). The new acceleration a₁' is calculated from from the equation a₁' = m₂a₂ / m₁, and the new acceleration a₂' is calculated accordingly. The collision is realized regardless whether the bounding circles ovelap or not.

See Also:

isOverlapping(Body)

toString

public java.lang.String toString()

Returns a string that contains the values of the attributes.

Overrides:

toString in class java.lang.Object