motionPathNode/motionPathNode.cpp

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

#include <maya/MDataHandle.h> 
#include <maya/MFnNumericAttribute.h> 
#include <maya/MFnPlugin.h> 
#include <maya/MIOStream.h>
#include <maya/MGlobal.h>
#include <maya/MMatrix.h>
#include <maya/MPxMotionPathNode.h> 
#include <maya/MQuaternion.h> 
#include <maya/MStatus.h> 
#include <maya/MTransformationMatrix.h>
#include <maya/MTypeId.h>
 
// Plugin MotionPathNode Class //

// INTRODUCTION:
//  This class will create a custom "motionPathNode" node which
//  illustrates how a developer can extend Maya's motionPath
//  functionality by creating a surfboard that follows a path.
//
// HOW TO USE THIS PLUG-IN:
//
// Part 1, Getting started
//  (1) Compile this plug-in.
//  (2) Load the compiled plug-in into Maya via the plug-in manager.
//  (3) Create an anim curve to define how the motion progresses along
//      the path. Here we assume the animation is 114 frames long and
//      progresses linearly in time.
//          string $ac = `createNode animCurveTU -n "animCurve"`;
//          setKeyframe -t 1 -v 0 $ac;
//          setKeyframe -t 114 -v 1 $ac;
//  (4) Create a path for the motion to navigate: we use a NURBS circle.
//          string $tmp[] = `circle -ch on -o on -nr 0 1 0 -r 16.688138`;
//          string $path = $tmp[0];
//  (5) Create a motionPathNode and connect the path and anim curve.
//          $mp = `createNode motionPathNode`;
//          setAttr ($mp+".fractionMode") true;
//          connectAttr ($ac+".output") ($mp+".uValue");
//          connectAttr ($path+".worldSpace[0]") ($mp+".geometryPath");
//
// Part 2, Translation along the path
//  (6) Create a surfboard and connect to the motionPathNode.
//          $tmp = `polySphere`;
//          scale 2 0.1 1;
//          string $sp = $tmp[0];
//          connectAttr ($mp+".allCoordinates") ($sp+".translate");
//  (7) Play the animation and the surfboard will move along the path,
//      wobbling back and forth. Change the "offset" plug to affect
//      the magnitude of the offset effect and change "wobbleRate" to
//      affect the frequency of the wobble.
//          currentTime 1;
//          play -wait;
//
// Part 3, Add rotation so the surfboard follows the path
//  (8) Turn on the "follow" attribute to enable rotation.
//          setAttr ($mp+".follow") 1;
//
//  (9) Define the axes then play again. The surfboard should
//      now follow the path.
//          setAttr ($mp+".frontAxis") 0;
//          setAttr ($mp+".upAxis") 1;
//          currentTime 1;
//          play -wait;
//
// Part 4, Make the surfboard bank into the curve
//  (10) Enable banking to add rotation based on the sharpness of
//       the curve by rotating the surfboard about the front vector.
//          setAttr ($mp+".bank") true;
//          setAttr ($mp+".bankScale") 5.0;
//

// Useful constants.
//
#define ALMOST_ZERO 1.0e-5
#define TWO_PI      ( 2.0 * 3.1415927 )

// Declare our motionPathNode class which derives from MPxMotionPath.
//
class motionPathNode : public MPxMotionPathNode
{
public:
                        motionPathNode();
                    ~motionPathNode() override; 

    MStatus     compute( const MPlug& plug, MDataBlock& data ) override;

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

    // Member variables...
    //
    static  MObject     offset;         // The "offset" attribute
    static  MObject     wobbleRate;     // The "wobbleRate" attribute

    static  MTypeId     id;             // The IFF type id

private:
    static MStatus      affectsOutput( MObject& attr );
};

// Attributes defined on this node.
//
MObject motionPathNode::offset;
MObject motionPathNode::wobbleRate;

// IFF type ID
// Each node requires a unique identifier which is used by
// MFnDependencyNode::create() to identify which node to create, and by
// the Maya file format.
//
// For local testing of nodes you can use any identifier between
// 0x00000000 and 0x0007ffff, but for any node that you plan to use for
// more permanent purposes, you should get a universally unique id from
// Autodesk Support. You will be assigned a unique range that you can manage
// on your own.
//
MTypeId motionPathNode::id( 0x0008101C );

// This node does not need to perform any special actions on creation or
// destruction
//
motionPathNode::motionPathNode()
{
}
motionPathNode::~motionPathNode()
{
}

// The compute() method does the actual work of the node using the inputs
// of the node to generate its output.
//
// Compute takes two parameters: plug and data.
// - Plug is the the data value that needs to be recomputed
// - Data provides handles to all of the nodes attributes, only these
//   handles should be used when performing computations.
//
MStatus motionPathNode::compute( const MPlug& plug, MDataBlock& data )
{
    double  f;
    MStatus status;

    // Read the attributes we need from the datablock.
    //
    double  uVal            = data.inputValue( uValue ).asDouble();
    bool    fractionModeVal = data.inputValue( fractionMode ).asBool();
    bool    followVal       = data.inputValue( follow ).asBool();
    int     frontAxisVal    = data.inputValue( frontAxis ).asShort();
    int     upAxisVal       = data.inputValue( upAxis ).asShort();
    bool    bankVal         = data.inputValue( bank ).asBool();
    double  bankScaleVal    = data.inputValue( bankScale ).asDouble();
    double  bankThresholdVal= data.inputValue( bankThreshold ).asDouble();
    double  offsetVal       = data.inputValue( offset ).asDouble();
    double  wobbleRateVal   = data.inputValue( wobbleRate ).asDouble();

    // Make sure the value is fractional.
    //
    if ( fractionModeVal ) {
        f = uVal;
    } else {
        f = parametricToFractional( uVal, &status );
    }
    CHECK_MSTATUS_AND_RETURN_IT( status );

    // To compute the sample location on the path, first wrap the fraction
    // around the start of the the path in case it goes past the end
    // to prevent clamping, then compute the sample location on the path.
    // 
    f = wraparoundFractionalValue( f, &status );
    CHECK_MSTATUS_AND_RETURN_IT( status );

    MPoint location = position( data, f, &status );
    CHECK_MSTATUS_AND_RETURN_IT( status );

    // Get the orthogonal vectors on the motion path.
    //
    const MVector worldUp = MGlobal::upAxis();
    MVector front, side, up;
    CHECK_MSTATUS_AND_RETURN_IT( getVectors( data, f, front, side, up,
            &worldUp ) );

    // If follow (i.e. rotation) is enabled, check if banking is also
    // enabled and if so, bank into the turn.
    //
    if ( followVal && bankVal ) {
        MQuaternion bankQuat = banking( data, f, worldUp,
                bankScaleVal, bankThresholdVal, &status );
        CHECK_MSTATUS_AND_RETURN_IT( status );
        up = up.rotateBy( bankQuat );
        side = front ^ up;
    }

    // Compute the wobble that moves the sphere back and forth as it
    // traverses the path.
    //
    if ( fabs( offsetVal ) > ALMOST_ZERO
                && fabs( wobbleRateVal ) > ALMOST_ZERO ) {
        double wobble = offsetVal * sin( TWO_PI * wobbleRateVal * f );
        MVector tmp = side * wobble;
        location += tmp;
    }

    // Write the result values to the output plugs.
    //
    data.outputValue( allCoordinates ).set( location.x, location.y,
            location.z );
    if ( followVal ) {
        MTransformationMatrix   resultOrientation = matrix( front, side,
                up, frontAxisVal, upAxisVal, &status );
        CHECK_MSTATUS_AND_RETURN_IT( status );
        MTransformationMatrix::RotationOrder ro
                = (MTransformationMatrix::RotationOrder)
                    ( data.inputValue( rotateOrder ).asShort() + 1 );
        double  rot[3];
        status = MTransformationMatrix( resultOrientation ).getRotation(
                rot, ro );
        CHECK_MSTATUS_AND_RETURN_IT( status );
        data.outputValue( rotate ).set( rot[0], rot[1], rot[2] );
    }
    
    return( MS::kSuccess );
}

// The creator() method allows Maya to instantiate instances of this node.
// It is called every time a new instance of the node is requested by
// either the createNode command or the MFnDependencyNode::create()
// method.
//
// In this case creator simply returns a new motionPathNode object.
//
void* motionPathNode::creator()
{
    return( new motionPathNode() );
}

// The initialize method is called only once when the node is first
// registered with Maya. In general,
//
MStatus motionPathNode::initialize()
{
    MFnNumericAttribute     nAttr;

    //====================================================================
    //          I N P U T     A T T R I B U T E S
    //====================================================================
    //
    offset = nAttr.create( "offset", "o",
            MFnNumericData::kDouble, 4.0 ); 
    addAttribute( offset );

    wobbleRate = nAttr.create( "wobbleRate", "w",
            MFnNumericData::kDouble, 10.0 ); 
    addAttribute( wobbleRate );

    //====================================================================
    //          A F F E C T S    R E L A T I O N S H I P S
    //====================================================================
    //
    CHECK_MSTATUS_AND_RETURN_IT( affectsOutput( offset ) );
    CHECK_MSTATUS_AND_RETURN_IT( affectsOutput( wobbleRate ) );

    return( MS::kSuccess );
}

MStatus motionPathNode::affectsOutput( MObject& attr )
{
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, rotate ) );
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, rotateX ) );
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, rotateY ) );
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, rotateZ ) );
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, allCoordinates ) );
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, xCoordinate ) );
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, yCoordinate ) );
    CHECK_MSTATUS_AND_RETURN_IT( attributeAffects( attr, zCoordinate ) );

    return( MS::kSuccess );
}

// These methods load and unload the plugin, registerNode registers the
// new node type with maya
//
MStatus initializePlugin( MObject obj )
{ 
    MStatus     status;
    MFnPlugin   plugin( obj );

    status = plugin.registerNode( "motionPathNode",
            motionPathNode::id,
            motionPathNode::creator,
            motionPathNode::initialize,
            MPxNode::kMotionPathNode );
    if (!status) {
        status.perror("registerNode");
        return( status );
    }

    return( status );
}

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

    status = plugin.deregisterNode( motionPathNode::id );
    if (!status) {
        status.perror("deregisterNode");
        return( status );
    }

    return( status );
}