spiralAnimCurveCmd/spiralAnimCurveCmd.cpp

//-
// ==========================================================================
// 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.
// ==========================================================================
//+

// DESCRIPTION:
// 
// Produces the MEL command "spiralAnimCurve".
//
// This plug-in attaches anim curves to the X, Y, and Z translation attributes
// of the selected objects, and then animates the object along a spiral path.
// This is a good example of attaching an anim curve to the attributes of an object.
//
// To use it:
//  (1) Select an object (or objects) in the Maya perspective window.
//  (2) Execute the command "spiralAnimCurve".
//  (3) Click the "play" button on the time slider.
//      The selected objects will move in a spiral as the animation plays. 
//

#include <math.h>
#include <maya/MIOStream.h>

#include <maya/MGlobal.h>
#include <maya/MFnPlugin.h> 
#include <maya/MSelectionList.h>
#include <maya/MItSelectionList.h>
#include <maya/MPoint.h>
#include <maya/MVector.h>
#include <maya/MMatrix.h>
#include <maya/MDagPath.h>
#include <maya/MFnAnimCurve.h>
#include <maya/MFnDagNode.h>
#include <maya/MPxCommand.h>
#include <maya/MString.h>

// Constants //

#define OUTWARD_VELOCITY 0.075
#define RADIAL_VELOCITY  0.05
#define NUM_FRAMES       120

// Class Definition //

class spiralAnimCurve : public MPxCommand {
public:

                    spiralAnimCurve() {};
    virtual         ~spiralAnimCurve();

    virtual MStatus doIt( const MArgList& args );
    static void*    creator();
};

// Class Implementation //

#define NUM_SPANS        30
#define WIDTH            10.0
#define VERTICAL_SCALING 4.0

spiralAnimCurve::~spiralAnimCurve() {}

void* spiralAnimCurve::creator()
{
    return new spiralAnimCurve();
}

// Set keyframes to move selected object in a spiral
MStatus spiralAnimCurve::doIt( const MArgList& )
{   
    // Get the Active Selection List
    //
    MStatus status;
    MSelectionList  sList;
    MGlobal::getActiveSelectionList( sList );

    // Create an iterator for the selection list
    //
    MItSelectionList iter( sList, MFn::kDagNode, &status );
    if ( MS::kSuccess != status ) {
        cerr << "Failure in plugin setup";
        return MS::kFailure;
    }
    
    MDagPath mObject;   
    MObject mComponent;

    for ( ; !iter.isDone(); iter.next() ) {
        status = iter.getDagPath( mObject, mComponent );

        // Check if there was an error
        //
        if ( MS::kSuccess != status ) continue;

        // We don't handle components
        //
        if ( !mComponent.isNull() ) continue;
        
        // Create the function set
        //
        MFnDagNode fnSet( mObject, &status );

        if ( MS::kSuccess != status ) {
            cerr << "Failure to create function set\n";
            continue;
        }

        // Get the plug for the X-translation channel
        //
        MString attrName( "translateX" );
        const MObject attrX = fnSet.attribute( attrName, &status );
        if ( MS::kSuccess != status ) {
            cerr << "Failure to find attribute\n";
        }
        MFnAnimCurve acFnSetX;
        acFnSetX.create( mObject.transform(), attrX, NULL, &status ); 

        if ( MS::kSuccess != status ) {
            cerr << "Failure creating MFnAnimCurve function set (translateX)\n";
            continue;
        }

        // Repeat for Y-translation
        //
        attrName.set( "translateZ" );
        const MObject attrZ = fnSet.attribute( attrName, &status );
        if ( MS::kSuccess != status ) {
            cerr << "Failure to find attribute\n";
        }
        MFnAnimCurve acFnSetZ;
        acFnSetZ.create( mObject.transform(), attrZ, NULL, &status ); 

        if ( MS::kSuccess != status ) {
            cerr << "Failure creating MFnAnimCurve function set (translateZ)\n";
            continue;
        }
        
        // Build spiral animation
        // 
        for( int i = 1; i <= NUM_FRAMES; i++ ) {
            // Build the keyframe at frame i
            //
            double x = sin( (double)i * RADIAL_VELOCITY ) * 
                            ( (double)i * OUTWARD_VELOCITY ); 
            double z = cos( (double)i * RADIAL_VELOCITY ) * 
                            ( (double)i * OUTWARD_VELOCITY );

            // cerr << "Setting keys - frame: " << i << "  x: " << x << "  z: " << z << endl;

            MTime tm( (double)i, MTime::kFilm );
            if ( ( MS::kSuccess != acFnSetX.addKeyframe( tm, x ) ) ||
                 ( MS::kSuccess != acFnSetZ.addKeyframe( tm, z ) ) ) {
                cerr << "Error setting the keyframe\n"; 
            }
        }

    }

    return status;
}

// Register command with system //

MStatus initializePlugin( MObject obj )
{ 
    MStatus   status;
    MFnPlugin plugin( obj, PLUGIN_COMPANY, "3.0", "Any");

    status = plugin.registerCommand( "spiralAnimCurve",
                                     spiralAnimCurve::creator ); 
    if (!status) {
        status.perror("registerCommand");
        return status;
    }
    
    return status;
}

MStatus uninitializePlugin( MObject obj )
{
    MStatus   status;
    MFnPlugin plugin( obj );

    status = plugin.deregisterCommand( "spiralAnimCurve" );
    if (!status) {
        status.perror("deregisterCommand");
        return status;
    }
    
    return status;
}