Jeffrey T. Palmer > Box2D > Box2D::b2ContactListener

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NAME ^

Box2D::b2ContactListener - Implement this class to get contact information.

SYNOPSIS ^

  package My::ContactListener;
  use Box2D;

  use base qw(Box2D::b2ContactListener);

  sub BeginContact {
      my ( $contact ) = @_;

      # Do something
  }

  sub EndContact {
      my ( $contact ) = @_;

      # Do something
  }

  sub PreSolve {
      my ( $contact, $manifold ) = @_;

      # Do something
  }

  sub PostSolve {
      my ( $contact, $impulse ) = @_;

      # Do something
  }

  1;

DESCRIPTION ^

Implement this class to get contact information. You can use these results for things like sounds and game logic. You can also get contact results by traversing the contact lists after the time step. However, you might miss some contacts because continuous physics leads to sub-stepping. Additionally you may receive multiple callbacks for the same contact in a single time step. You should strive to make your callbacks efficient because there may be many callbacks per time step.

Warning: You cannot create/destroy Box2D entities inside these callbacks.

METHODS ^

new()

Creates and returns a new Box2D::b2ContactListener. This is an inheritance friendly sub so you're free to leave it as default. Remember to call super in your own code, don't forget to call this!

Returns a Box2D::b2ContactListener

BeginContact( $contact )

Called when two fixtures begin to touch.

Parameters:

EndContact( $contact )

Called when two fixtures cease to touch.

Parameters:

PreSolve( $contact, $manifold )

This is called after a contact is updated. This allows you to inspect a contact before it goes to the solver. If you are careful, you can modify the contact manifold (e.g. disable contact). A copy of the old manifold is provided so that you can detect changes.

Note: this is called only for awake bodies.

Note: this is called even when the number of contact points is zero.

Note: this is not called for sensors.

Note: if you set the number of contact points to zero, you will not get an EndContact callback. However, you may get a BeginContact callback the next step.

Parameters:

PostSolve( $contact, $impulse )

This lets you inspect a contact after the solver is finished. This is useful for inspecting impulses.

Note: the contact manifold does not include time of impact impulses, which can be arbitrarily large if the sub-step is small. Hence the impulse is provided explicitly in a separate data structure.

Note: this is only called for contacts that are touching, solid, and awake.

Parameters:

setOurListeners()

This is private don't bother calling it unless you inherit and need to initialize.

Note: $self->{_listener} needs to be a Box2D::PerlContactListener.

SEE ALSO ^

BUGS ^

See "BUGS" in Box2D

AUTHORS ^

See "AUTHORS" in Box2D

COPYRIGHT & LICENSE ^

See "COPYRIGHT & LICENSE" in Box2D

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