net.algart.model3d.common.movement.model
Class EarthGravitationRule

java.lang.Object
  net.algart.model3d.common.movement.model.EarthGravitationRule

All Implemented Interfaces:

InteractionRule

public final class EarthGravitationRule
extends java.lang.Object
implements InteractionRule

Interaction between Earth and any having mass item. In this class, isApplicable method returns true if and only if byItem instanceof Earth and toItem instanceof HavingMass, and in this case calculateForce method fills resultXYZ vector by the force F=(0,0,−mg), where m=toItem.getMass(), g=byItem.getGravity().

This class is immutable and thread-safe: there are no ways to modify settings of the created instance.

AlgART Laboratory 2010

Since:

JDK 1.5

Version:

1.0

Author:

Daniel Alievsky

EarthGravitationRule

public EarthGravitationRule()

isApplicable

public boolean isApplicable(Item toItem,
                            Item byItem)

Description copied from interface: InteractionRule

Checks whether this interaction type is applicable to the given items. If this method returns false, there is a guarantee that InteractionRule.calculateForce(double[], Item, Item, double) method fills its result (first 3 elements of resultXYZ array) by 0.0. If this method returns true, then with high probability InteractionRule.calculateForce(double[], Item, Item, double) method returns a non-zero force.

The arguments of this method can be null; in this case, this method returns false.

Specified by:

isApplicable in interface InteractionRule

Parameters:

toItem - the item to which byItem acts; can be null, then this method returns false.

byItem - the acting item; can be null, then this method returns false.

Returns:

true if this interaction type can be used for this pair; false if byItem cannot act to toItem.

calculateForce

public boolean calculateForce(double[] resultXYZ,
                              Item toItem,
                              Item byItem,
                              double time)

Description copied from interface: InteractionRule

Calculates the force F=(F_x,F_y,F_z) of the action of byItem to toItem and returns it in first 3 elements of resultXYZ array (x-component F_x resultXYZ[0], y-component F_y in resultXYZ[1], z-component F_z in resultXYZ[2]). Returns false if the force is zero. Usually returns true is the force is non-zero, by it is allowed to return true even if it is zero.

This method must work correctly (return false and zero resulting force) also in all situations, when InteractionRule.isApplicable(Item, Item) method returns false.

Specified by:

calculateForce in interface InteractionRule

Parameters:

resultXYZ - resulting force (x-component in resultXYZ[0], y-component in resultXYZ[1], z-component in resultXYZ[2]).

toItem - the item to which byItem acts.

byItem - the acting item.

time - the current time (some interaction can change behaviour in time).

Returns:

if false, there is a guarantee that returned force is zero.