Module org.dyn4j

Package org.dyn4j.collision

Package containing supporting classes to detect collisions between Convex Shapes.

Collision detection can be an expensive process. To avoid unnecessary processing a two phase approach to collision detection is used. First a inaccurate, yet conservative, algorithm is used to detect possible collision pairs. This process is called the broad-phase. Next, after obtaining all the possible collision pairs, each pair is tested using an accurate algorithm. This is called the narrow-phase. After the narrow-phase is complete, another phase, Manifold generation, generates the contact points.

Broad-phase

The BroadphaseDetectors will determine whether two Convex Shapes can possibly penetrate, returning only valid CollisionPairs, which should then be sent to a NarrowphaseDetector.

Narrow-phase

The NarrowphaseDetectors will determine whether two Convex Shapes penetrate and return a Penetration.

The Penetration object represents the minimum distance along some vector required to push the Shapes out of the penetration.

The narrow-phase also contains classes for supporting multiple detectors at once via the FallbackNarrowphaseDetector class. Using the FallbackConditions the detector will determine whether to use the primary NarrowphaseDetector or the fallback.

Manifold Generation

Once a Penetration object is obtained, it should be passed to a ManifoldSolver. A ManifoldSolver will use the Penetration object and the given Convex Shapes to create a collision Manifold.

A collision Manifold represents the collision point(s) between the two Convex Shapes.

Continuous Collision Detection (CCD) and Raycasting

The process outlined above is called discrete collision detection. Outside of this process, there's continuous collision detection and raycasting.

Continuous collision detection (CCD) is the process of detecting missed collisions that the discrete process couldn't detect. The discrete process fails to detect some collisions due to it being run on a set interval - if a sufficiently small object is going fast enough, for example. CCD detectors implement the TimeOfImpactDetector interface and return a TimeOfImpact object when a collision is detected.

This package also supports raycasting for both the broad and narrow phases. These detectors implement the RaycastDetector interface and return Raycast objects when a ray hits a Fixture.

The following is a list of implementations of the above interfaces:

• BroadphaseDetectors
  • DynamicAABBTree [DEFAULT]
  • Sap
• NarrowphaseDetector
  • Gjk [DEFAULT]
  • Sat
• ManifoldSolver
  • ClippingManifoldSolver
• TimeOfImpactDetector
  • ConservativeAdvancement
• RaycastDetector
  • Gjk

Since:

1.0.0

Version:

4.0.0

Author:

William Bittle

Interface Summary

Interface	Description
Bounds	Represents the Bounds of a simulation.
CollisionBody<T extends Fixture>	Represents an object that can collide with other objects.
CollisionItem<T extends CollisionBody<E>,E extends Fixture>	Represents a grouping of a CollisionBody and Fixture.
CollisionPair<T>	Represents a collision between two CollisionBody's Fixtures.
Filter	Interface representing a filter for collision detection.
FixtureModificationHandler<T extends Fixture>	Represents a hook into a CollisionBody to be notified of Fixture modification events.

Class Summary

Class	Description
AbstractBounds	Abstract implementation of the Bounds interface.
AbstractCollisionBody<T extends Fixture>	A base implementation of the CollisionBody interface.
AbstractCollisionItem<T extends CollisionBody<E>,E extends Fixture>	Abstract implementation of the CollisionItem interface.
AbstractCollisionPair<T>	Abstract implementation of the CollisionPair interface.
AxisAlignedBounds	Represents a bounding region that is an Axis-Aligned bounding box.
BasicCollisionItem<T extends CollisionBody<E>,E extends Fixture>	Represents a basic, immutable implementation of the CollisionItem interface.
BasicCollisionPair<T>	Represents a basic, immutable implementation of the CollisionPair interface.
CategoryFilter	A Filter for categorized fixtures.
Collisions	Class used to estimate collision counts and other one-off collision methods and values.
Fixture	Represents a geometric piece of a CollisionBody.
TypeFilter	A base implementation of a class hierarchy Fixture Filter.