reactphysics3d/src/constraint/FixedJoint.h

/********************************************************************************
* ReactPhysics3D physics library, http://code.google.com/p/reactphysics3d/      *
* Copyright (c) 2010-2013 Daniel Chappuis                                       *
*********************************************************************************
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* This software is provided 'as-is', without any express or implied warranty.   *
* In no event will the authors be held liable for any damages arising from the  *
* use of this software.                                                         *
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* including commercial applications, and to alter it and redistribute it        *
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*    that you wrote the original software. If you use this software in a        *
*    product, an acknowledgment in the product documentation would be           *
*    appreciated but is not required.                                           *
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* 2. Altered source versions must be plainly marked as such, and must not be    *
*    misrepresented as being the original software.                             *
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* 3. This notice may not be removed or altered from any source distribution.    *
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#ifndef REACTPHYSICS3D_FIXED_JOINT_H
#define REACTPHYSICS3D_FIXED_JOINT_H

// Libraries
#include "Constraint.h"
#include "../mathematics/mathematics.h"

namespace reactphysics3d {

// Structure FixedJointInfo
/**
 * This structure is used to gather the information needed to create a fixed
 * joint. This structure will be used to create the actual fixed joint.
 */
struct FixedJointInfo : public ConstraintInfo {

    public :

        // -------------------- Attributes -------------------- //

        /// Anchor point (in world-space coordinates)
        Vector3 anchorPointWorldSpace;

        /// Constructor
        FixedJointInfo(RigidBody* rigidBody1, RigidBody* rigidBody2,
                       const Vector3& initAnchorPointWorldSpace)
                       : ConstraintInfo(rigidBody1, rigidBody2, FIXEDJOINT),
                         anchorPointWorldSpace(initAnchorPointWorldSpace){}
};

// Class FixedJoint
/**
 * This class represents a fixed joint that is used to forbid any translation or rotation
 * between two bodies.
 */
class FixedJoint : public Constraint {

    private :

        // -------------------- Constants -------------------- //

        // Beta value for the bias factor of position correction
        static const decimal BETA;

        // -------------------- Attributes -------------------- //

        /// Anchor point of body 1 (in local-space coordinates of body 1)
        Vector3 mLocalAnchorPointBody1;

        /// Anchor point of body 2 (in local-space coordinates of body 2)
        Vector3 mLocalAnchorPointBody2;

        /// Vector from center of body 2 to anchor point in world-space
        Vector3 mR1World;

        /// Vector from center of body 2 to anchor point in world-space
        Vector3 mR2World;

        /// Inertia tensor of body 1 (in world-space coordinates)
        Matrix3x3 mI1;

        /// Inertia tensor of body 2 (in world-space coordinates)
        Matrix3x3 mI2;

        /// Accumulated impulse for the 3 translation constraints
        Vector3 mImpulseTranslation;

        /// Accumulate impulse for the 3 rotation constraints
        Vector3 mImpulseRotation;

        /// Inverse mass matrix K=JM^-1J^-t of the 3 translation constraints (3x3 matrix)
        Matrix3x3 mInverseMassMatrixTranslation;

        /// Inverse mass matrix K=JM^-1J^-t of the 3 rotation constraints (3x3 matrix)
        Matrix3x3 mInverseMassMatrixRotation;

        /// Bias vector for the 3 translation constraints
        Vector3 mBiasTranslation;

        /// Bias vector for the 3 rotation constraints
        Vector3 mBiasRotation;

        /// Inverse of the initial orientation difference between the two bodies
        Quaternion mInitOrientationDifferenceInv;

    public :

        // -------------------- Methods -------------------- //

        /// Constructor
        FixedJoint(const FixedJointInfo& jointInfo);

        /// Destructor
        virtual ~FixedJoint();

        /// Return the number of bytes used by the joint
        virtual size_t getSizeInBytes() const;

        /// Initialize before solving the constraint
        virtual void initBeforeSolve(const ConstraintSolverData& constraintSolverData);

        /// Warm start the constraint (apply the previous impulse at the beginning of the step)
        virtual void warmstart(const ConstraintSolverData& constraintSolverData);

        /// Solve the velocity constraint
        virtual void solveVelocityConstraint(const ConstraintSolverData& constraintSolverData);

        /// Solve the position constraint (for position error correction)
        virtual void solvePositionConstraint(const ConstraintSolverData& constraintSolverData);
};

// Return the number of bytes used by the joint
inline size_t FixedJoint::getSizeInBytes() const {
    return sizeof(FixedJoint);
}

}

#endif