dynExprField/dynExprField.h

//-
// ==========================================================================
// Copyright 2015 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.
// ==========================================================================
//+

//  Description
//  The dynExprField node implements a uniform field, which allows 
//      the per particle attributes to drive the field's attributes.
//

#include <maya/MIOStream.h>
#include <maya/MVector.h>
#include <maya/MObject.h>
#include <maya/MPlug.h>
#include <maya/MDataBlock.h>
#include <maya/MFnPlugin.h>
#include <maya/MPxFieldNode.h>
#include <maya/MGL.h>

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

class dynExprField: public MPxFieldNode
{
public:
    dynExprField() {};
    ~dynExprField() override {};

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

    // will compute output force.
    //
    MStatus compute( const MPlug& plug, MDataBlock& block ) override;

    MStatus iconSizeAndOrigin(  GLuint& width,
                        GLuint& height,
                        GLuint& xbo,
                        GLuint& ybo   ) override;
    MStatus iconBitmap(GLubyte* bitmap) override;

    //
    // attributes.
    //

    // direction of the force
    //
    static MObject  mDirection;

    // Other data members
    //
        static MTypeId  id;

private:

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

    MVector direction(MDataBlock& block);

    // Compute the force to apply to each particle
    void apply(MDataBlock         &block,
           int                 receptorSize,
           const MDoubleArray &magnitudeArray,
           const MDoubleArray &magnitudeOwnerArray,
           const MVectorArray &directionArray,
           const MVectorArray &directionOwnerArray,
           MVectorArray       &outputForce);
};