OMK::Iii::BallJoint Class Reference
[Joints]

Ball joint. More...

#include <OMKJoint.h>

Inheritance diagram for OMK::Iii::BallJoint:

[legend]Collaboration diagram for OMK::Iii::BallJoint:

[legend]List of all members.

Protected Member Functions
Interface
virtual void	establishLink ()
	Initialises the link reference positions.
virtual bool	retroPropagation ()
	Calculates the ideal position of the reference point.
virtual void	currentObjectPosition ()
	Calculates the current position of the object.
Protected Attributes
Internal parameters.
OMK::Type::Transform	_newObjectPosition
	The object position computed in retroPropagation.
OMK::Type::Transform	_refObjectOffset
	The reference.
bool	_alreadyKnow
	Flag to avoid the calculate twice the position.
float	_radius
	the radius of the ball.
Wm4::Vector3f	_previousPosition
	Previous object position translate to compute the translation.
bool	_reset
	Flag to reset the _previousPosition.
Private Member Functions
	DECLARE_JOINT_FACTORY (BallJoint)

---

Detailed Description

Ball joint.

Date:

2007-06-20

Author:

Beno� Chanclou

An object linked with this extension rotate to a constant distant form the joint position.

Parameters are the same as the lock joint.

The following configuration can be used to lock an object on an other one.

object
{
  ...
    joint
    {
      class Joint
      ...
      Joint Ball // The ball joint
      Attribute Position // The name of the attribute (by default "Position")
      ...
    }
  ...
}

If the object is translated, it try to move the reference position. If the object is rotated, it turns around the joint position.

Definition at line 278 of file OMKJoint.h.

---

Member Function Documentation

OMK::Iii::BallJoint::DECLARE_JOINT_FACTORY

(

BallJoint

)

[private]

void OMK::Iii::BallJoint::establishLink

(

)

[protected, virtual]

Initialises the link reference positions.

Reimplemented from OMK::Iii::Joint.

Definition at line 120 of file OMKJoint.cpp.

References _newObjectPosition, OMK::Iii::Joint::_objectOffset, OMK::Iii::Joint::_objectPosition, _radius, _refObjectOffset, _reset, OMK::Iii::Joint::establishLink(), OMK::IAccessorT< T >::get(), and OMK::Type::Transform::getTranslate().

{
  Joint::establishLink() ;
  _radius = _objectOffset.getTranslate().Length() ;
  
    // stores the reference offset
  _refObjectOffset = _objectOffset ;
  _newObjectPosition = _objectPosition->get() ;
  _reset = true ;
}

bool OMK::Iii::BallJoint::retroPropagation

(

)

[protected, virtual]

Calculates the ideal position of the reference point.

Reimplemented from OMK::Iii::Joint.

Definition at line 131 of file OMKJoint.cpp.

References _alreadyKnow, OMK::Iii::Joint::_jointOffsetInverse, OMK::Iii::Joint::_jointPosition, _newObjectPosition, OMK::Iii::Joint::_objectOffset, OMK::Iii::Joint::_objectOffsetInverse, OMK::Iii::Joint::_objectPosition, _previousPosition, _radius, OMK::Iii::Joint::_referencePosition, _refObjectOffset, _reset, OMK::IAccessorT< T >::get(), OMK::Type::Transform::getRotate(), OMK::Type::Transform::getTranslate(), OMK::Type::Transform::inverse(), OMK::Type::product(), OMK::IAccessorT< T >::set(), OMK::Type::Transform::setRotate(), OMK::Type::Transform::setTranslate(), and OMK::Type::Transform::updateFlags().

{
  if( _reset )
  {
    _previousPosition = _objectPosition->get().getTranslate() ;
    _reset = false ;
  }
  // Get the joint axis and perpendicular plane
  Wm4::Vector3f axis( _refObjectOffset.getTranslate() ) ;
  axis.Normalize() ;
  
  // the reference position according to the position of the joint and the reference offset
  OMK::Type::Transform refObjectPosition( product( _jointPosition->get(), _refObjectOffset ) ) ;
  
  // The reference orientation
  Wm4::Matrix3f refOrientation = _jointPosition->get().getRotate() ;
  // get the new orientation
  Wm4::Matrix3f newOrientation = _objectPosition->get().getRotate() * ( refObjectPosition.getRotate().Transpose() * refOrientation ) ;
  
  // Only the translation
  bool isConstraint = _objectPosition->get().getTranslate() != refObjectPosition.getTranslate() ;
  
  // The new object position
  // = the position of the joint
  // + the position along the axis
  _newObjectPosition.setTranslate( _jointPosition->get().getTranslate() + ( newOrientation * axis ) * _radius ) ;
  _newObjectPosition.setRotate( newOrientation ) ;
  _alreadyKnow = true ;
  // update the current object offset
  _objectOffset = product( _jointPosition->get().inverse(), _newObjectPosition ) ;
  _objectOffset.updateFlags() ;
  _objectOffsetInverse = _objectOffset.inverse() ;
  _objectOffsetInverse.updateFlags() ;

  if( isConstraint )
  {
    // Calculates the optimal position of the reference position to retro-propagates
    OMK::Type::Transform newJointPosition( _jointPosition->get().getTranslate() 
                                        + _objectPosition->get().getTranslate() 
                                        - _previousPosition,
                                          _jointPosition->get().getRotate() ) ;
    _referencePosition->set( product( newJointPosition, _jointOffsetInverse ) ) ;
    _reset = true ;
  }

  return isConstraint ;
}

void OMK::Iii::BallJoint::currentObjectPosition

(

)

[protected, virtual]

Calculates the current position of the object.

Reimplemented from OMK::Iii::Joint.

Definition at line 179 of file OMKJoint.cpp.

References _alreadyKnow, OMK::Iii::Joint::_jointPosition, _newObjectPosition, OMK::Iii::Joint::_objectOffset, OMK::Iii::Joint::_objectPosition, OMK::IAccessorT< T >::get(), OMK::Type::product(), and OMK::IAccessorT< T >::set().

{
  if( _alreadyKnow )
  {
    _alreadyKnow = false ;
    _objectPosition->set( _newObjectPosition ) ;
  }
  else
  {
    // calculates the new object position
    _objectPosition->set( product( _jointPosition->get(), _objectOffset ) ) ;
  }
}

---

Member Data Documentation

OMK::Type::Transform OMK::Iii::BallJoint::_newObjectPosition [protected]

The object position computed in retroPropagation.

This value is stored to optimise the compute.

Definition at line 295 of file OMKJoint.h.

Referenced by currentObjectPosition(), establishLink(), and retroPropagation().

OMK::Type::Transform OMK::Iii::BallJoint::_refObjectOffset [protected]

The reference.

Definition at line 297 of file OMKJoint.h.

Referenced by establishLink(), and retroPropagation().

bool OMK::Iii::BallJoint::_alreadyKnow [protected]

Flag to avoid the calculate twice the position.

Definition at line 299 of file OMKJoint.h.

Referenced by currentObjectPosition(), and retroPropagation().

float OMK::Iii::BallJoint::_radius [protected]

the radius of the ball.

Its value is set during the establishLink call.

Definition at line 302 of file OMKJoint.h.

Referenced by establishLink(), and retroPropagation().

Wm4::Vector3f OMK::Iii::BallJoint::_previousPosition [protected]

Previous object position translate to compute the translation.

Definition at line 304 of file OMKJoint.h.

Referenced by retroPropagation().

bool OMK::Iii::BallJoint::_reset [protected]

Flag to reset the _previousPosition.

Definition at line 306 of file OMKJoint.h.

Referenced by establishLink(), and retroPropagation().

---