simpleSpring/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>



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

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

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

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

    // Override applySpringLaw.
    //
    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 ) override;


    //=================================================================
    // 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 );
}