simpleSpring.h

//-
// ==========================================================================
// Copyright 1995,2006,2008 Autodesk, Inc. All rights reserved.
//
// Use of this software is subject to the terms of the Autodesk
// license agreement provided at the time of installation or download,
// or which otherwise accompanies this software in either electronic
// or hard copy form.
// ==========================================================================
//+

#include <maya/MIOStream.h>
#include <maya/MTime.h>
#include <maya/MVector.h>
#include <maya/MObject.h>
#include <maya/MPlug.h>
#include <maya/MDataBlock.h>
#include <maya/MFnPlugin.h>
#include <maya/MPxSpringNode.h>


class MIntArray;
class MVectorArray;

#define McheckErr(stat, msg)            \
        if ( MS::kSuccess != stat )             \
        {                                                               \
                cerr << msg;                            \
                return MS::kFailure;            \
        }

class simpleSpring: public MPxSpringNode
{
public:
        simpleSpring();
        virtual ~simpleSpring();

        static void             *creator();
        static MStatus  initialize();

        // will be used to get user defined attributes
        //
        virtual MStatus compute( const MPlug& plug, MDataBlock& block );

        // Override applySpringLaw.
        //
        virtual MStatus applySpringLaw( double stiffness,
                                                double damping, double restLength,
                                                double endMass1, double endMass2,
                                                const MVector &endP1, const MVector &endP2,
                                                const MVector &endV1, const MVector &endV2,
                                                MVector &forceV1, MVector &forceV2 );


        //=================================================================
        // If you need new attributes, add them here. Below is an example.
        //=================================================================

        // Your numeric attribute
        //
        static MObject  aSpringFactor;

        // Other data members
        //
        static MTypeId  id;

    // INLINEs to get attribute value.
    //
    double  end1WeightValue( MDataBlock& block );
    double  end2WeightValue( MDataBlock& block );

private:

        // methods to get attribute value.
        //
        double  springFactor( MDataBlock& block );

        // A parameter for this simple spring node.
        //
        double  factor;
};

// inlines
//
inline double simpleSpring::springFactor( MDataBlock& block )
{
        MStatus status;

        MDataHandle hValue = block.inputValue( aSpringFactor, &status );

        double value = 0.0;
        if( status == MS::kSuccess )
                value = hValue.asDouble();

        return( value );
}


// INLINE
//
inline double simpleSpring::end1WeightValue( MDataBlock& block )
{
        MStatus status;
        MDataHandle hValue = block.inputValue( mEnd1Weight, &status );

        double value = 0.0;
        if( status == MS::kSuccess )
                value = hValue.asDouble();

        return( value );
}

inline double simpleSpring::end2WeightValue( MDataBlock& block )
{
        MStatus status;
        MDataHandle hValue = block.inputValue( mEnd2Weight, &status );

        double value = 0.0;
        if( status == MS::kSuccess )
                value = hValue.asDouble();

        return( value );
}