Package org.jbox2d.dynamics.joints

Class JointDef

java.lang.Object
org.jbox2d.dynamics.joints.JointDef
Direct Known Subclasses:
ConstantVolumeJointDef, DistanceJointDef, FrictionJointDef, GearJointDef, MotorJointDef, MouseJointDef, PrismaticJointDef, PulleyJointDef, RevoluteJointDef, RopeJointDef, WeldJointDef, WheelJointDef
public class JointDef extends Object
Joint definitions are used to construct joints.

Each joint type has a definition that derives from JointDef. All joints are connected between two different bodies. One body may static. Joints between static and/or kinematic bodies are allowed, but have no effect and use some processing time.

You can specify user data for any joint type and you can provide a flag to prevent the attached bodies from colliding with each other. This is actually the default behavior and you must set the collideConnected Boolean to allow collision between to connected bodies.

Many joint definitions require that you provide some geometric data. Often a joint will be defined by anchor points. These are points fixed in the attached bodies. jbox2d requires these points to be specified in local coordinates. This way the joint can be specified even when the current body transforms violate the joint constraint - a common occurrence when a game is saved and reloaded. Additionally, some joint definitions need to know the default relative angle between the bodies. This is necessary to constrain rotation correctly.

Initializing the geometric data can be tedious, so many joints have initialization functions that use the current body transforms to remove much of the work. However, these initialization functions should usually only be used for prototyping. Production code should define the geometry directly. This will make joint behavior more robust.

The rest of the joint definition data depends on the joint type.

https://box2d.org/documentation/md__d_1__git_hub_box2d_docs_dynamics.html#autotoc_md82
Author:
Daniel Murphy

  • Field Details

    • type

      public JointType type
      The joint type is set automatically for concrete joint types.

    • userData

      public Object userData
      Use this to attach application specific data to your joints.

    • bodyA

      public Body bodyA
      The first attached body.

    • bodyB

      public Body bodyB
      The second attached body.

    • collideConnected

      public boolean collideConnected
      Set this flag to true if the attached bodies should collide.

  • Constructor Details