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# sweptEmitter.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.
    // ==========================================================================
    //+

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

    #include <sweptEmitter.h>

    #include <maya/MDataHandle.h>
    #include <maya/MFnDynSweptGeometryData.h>
    #include <maya/MDynSweptLine.h>
    #include <maya/MDynSweptTriangle.h>

    #include <maya/MVectorArray.h>
    #include <maya/MDoubleArray.h>
    #include <maya/MIntArray.h>
    #include <maya/MMatrix.h>

    #include <maya/MFnDependencyNode.h>
    #include <maya/MFnNumericAttribute.h>
    #include <maya/MFnUnitAttribute.h>
    #include <maya/MFnVectorArrayData.h>
    #include <maya/MFnDoubleArrayData.h>
    #include <maya/MFnArrayAttrsData.h>
    #include <maya/MFnMatrixData.h>

    MTypeId sweptEmitter::id( 0x80016 );

    sweptEmitter::sweptEmitter()
    :   lastWorldPoint(0, 0, 0, 1)
    {
    }

    sweptEmitter::~sweptEmitter()
    {
    }

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

    MStatus sweptEmitter::initialize()
    //
    //  Descriptions:
    //      Initialize the node, create user defined attributes.
    //
    {
        return( MS::kSuccess );
    }

    MStatus sweptEmitter::compute(const MPlug& plug, MDataBlock& block)
    //
    //  Descriptions:
    //      Call emit emit method to generate new particles.
    //
    {
        MStatus status;

        // Determine if we are requesting the output plug for this emitter node.
        //
        if( !(plug == mOutput) )
            return( MS::kUnknownParameter );

        // Get the logical index of the element this plug refers to,
        // because the node can be emitting particles into more
        // than one particle shape.
        //
        int multiIndex = plug.logicalIndex( &status );
        McheckErr(status, "ERROR in plug.logicalIndex.\n");

        // Get output data arrays (position, velocity, or parentId)
        // that the particle shape is holding from the previous frame.
        //
        MArrayDataHandle hOutArray = block.outputArrayValue(mOutput, &status);
        McheckErr(status, "ERROR in hOutArray = block.outputArrayValue.\n");

        // Create a builder to aid in the array construction efficiently.
        //
        MArrayDataBuilder bOutArray = hOutArray.builder( &status );
        McheckErr(status, "ERROR in bOutArray = hOutArray.builder.\n");

        // Get the appropriate data array that is being currently evaluated.
        //
        MDataHandle hOut = bOutArray.addElement(multiIndex, &status);
        McheckErr(status, "ERROR in hOut = bOutArray.addElement.\n");

        // Get the data and apply the function set.
        //
        MFnArrayAttrsData fnOutput;
        MObject dOutput = fnOutput.create ( &status );
        McheckErr(status, "ERROR in fnOutput.create.\n");

        // Check if the particle object has reached it's maximum,
        // hence is full. If it is full then just return with zero particles.
        //
        bool beenFull = isFullValue( multiIndex, block );
        if( beenFull )
        {
            return( MS::kSuccess );
        }

        // Get deltaTime, currentTime and startTime.
        // If deltaTime <= 0.0, or currentTime <= startTime,
        // do not emit new pariticles and return.
        //
        MTime cT = currentTimeValue( block );
        MTime sT = startTimeValue( multiIndex, block );
        MTime dT = deltaTimeValue( multiIndex, block );
        if( (cT <= sT) || (dT <= 0.0) )
        {
            // We do not emit particles before the start time,
            // and do not emit particles when moving backwards in time.
            //

            // This code is necessary primarily the first time to
            // establish the new data arrays allocated, and since we have
            // already set the data array to length zero it does
            // not generate any new particles.
            //
            hOut.set( dOutput );
            block.setClean( plug );

            return( MS::kSuccess );
        }

        // Get speed, direction vector, and inheritFactor attributes.
        //
        double speed = speedValue( block );
        MVector dirV = directionVector( block );
        double inheritFactor = inheritFactorValue( multiIndex, block );

        // Get the position and velocity arrays to append new particle data.
        //
        MVectorArray fnOutPos = fnOutput.vectorArray("position", &status);
        MVectorArray fnOutVel = fnOutput.vectorArray("velocity", &status);

        // Convert deltaTime into seconds.
        //
        double dt = dT.as( MTime::kSeconds );

        // Apply rotation to the direction vector
        MVector rotatedV = useRotation ( dirV );

        // position,
        MVectorArray inPosAry;
        // velocity
        MVectorArray inVelAry;
        // emission rate
        MIntArray emitCountPP;

        // Get the swept geometry data
        //
        MObject thisObj = this->thisMObject();
        MPlug sweptPlug( thisObj, mSweptGeometry );

        if ( sweptPlug.isConnected() )
        {
            MDataHandle sweptHandle = block.inputValue( mSweptGeometry );
            // MObject sweptData = sweptHandle.asSweptGeometry();
            MObject sweptData = sweptHandle.data();
            MFnDynSweptGeometryData fnSweptData( sweptData );

            // Curve emission
            //
            if (fnSweptData.lineCount() > 0) {
                int numLines = fnSweptData.lineCount();

                for ( int i=0; i<numLines; i++ )
                {
                    inPosAry.clear();
                    inVelAry.clear();
                    emitCountPP.clear();

                    MDynSweptLine line = fnSweptData.sweptLine( i );

                    // ... process current line ...
                    MVector p1 = line.vertex( 0 );
                    MVector p2 = line.vertex( 1 );

                    inPosAry.append( p1 );
                    inPosAry.append( p2 );

                    inVelAry.append( MVector( 0,0,0 ) );
                    inVelAry.append( MVector( 0,0,0 ) );

                    // emit Rate for two points on line
                    emitCountPP.clear();
                    status = emitCountPerPoint( plug, block, 2, emitCountPP );

                    emit( inPosAry, inVelAry, emitCountPP,
                        dt, speed, inheritFactor, rotatedV, fnOutPos, fnOutVel );

                }
            }

            // Surface emission (nurb or polygon)
            //
            if (fnSweptData.triangleCount() > 0) {
                int numTriangles = fnSweptData.triangleCount();

                for ( int i=0; i<numTriangles; i++ )
                {
                    inPosAry.clear();
                    inVelAry.clear();
                    emitCountPP.clear();

                    MDynSweptTriangle tri = fnSweptData.sweptTriangle( i );

                    // ... process current triangle ...
                    MVector p1 = tri.vertex( 0 );
                    MVector p2 = tri.vertex( 1 );
                    MVector p3 = tri.vertex( 2 );

                    MVector center = p1 + p2 + p3;
                    center /= 3.0;

                    inPosAry.append( center );

                    inVelAry.append( MVector( 0,0,0 ) );

                    // emit Rate for two points on line
                    emitCountPP.clear();
                    status = emitCountPerPoint( plug, block, 1, emitCountPP );

                    emit( inPosAry, inVelAry, emitCountPP,
                        dt, speed, inheritFactor, rotatedV, fnOutPos, fnOutVel );

                }
            }
        }

        // Update the data block with new dOutput and set plug clean.
        //
        hOut.set( dOutput );
        block.setClean( plug );

        return( MS::kSuccess );
    }

    void sweptEmitter::emit
        (
            const MVectorArray &inPosAry,   // points where new particles from
            const MVectorArray &inVelAry,   // initial velocity of new particles
            const MIntArray &emitCountPP,   // # of new particles per point
            double dt,                      // elapsed time
            double speed,                   // speed factor
            double inheritFactor,           // for inherit velocity
            MVector dirV,                   // emit direction
            MVectorArray &outPosAry,        // holding new particles position
            MVectorArray &outVelAry         // holding new particles velocity
        )
    //
    //  Descriptions:
    //
    {
        // check the length of input arrays.
        //
        int posLength = inPosAry.length();
        int velLength = inVelAry.length();
        int countLength = emitCountPP.length();
        if( (posLength != velLength) || (posLength != countLength) )
            return;

        // Compute total emit count.
        //
        int index;
        int totalCount = 0;
        for( index = 0; index < countLength; index ++ )
            totalCount += emitCountPP[index];

        if( totalCount <= 0 )
            return;

        // Map direction vector into world space and normalize it.
        //
        dirV.normalize();

        // Start emission.
        //
        int emitCount;
        MVector newPos, newVel;
        MVector prePos, sPos, sVel;
        for( index = 0; index < posLength; index++ )
        {
            emitCount = emitCountPP[index];
            if( emitCount <= 0 )
                continue;

            sPos = inPosAry[index];
            sVel = inVelAry[index];
            prePos = sPos - sVel * dt;

            for( int i = 0; i < emitCount; i++ )
            {
                double alpha = ( (double)i + drand48() ) / (double)emitCount;
                newPos = (1 - alpha) * prePos + alpha * sPos;
                newVel = dirV * speed;

                newPos += newVel * ( dt * (1 - alpha) );
                newVel += sVel * inheritFactor;

                // Add new data into output arrays.
                //
                outPosAry.append( newPos );
                outVelAry.append( newVel );
            }
        }

    }

    MVector sweptEmitter::useRotation ( MVector &direction )
    {
        MStatus status;
        MVector rotatedVector;

        MObject thisNode = thisMObject();
        MFnDependencyNode fnThisNode( thisNode );

        // get worldMatrix attribute.
        //
        MObject worldMatrixAttr = fnThisNode.attribute( "worldMatrix" );

        // build worldMatrix plug, and specify which element the plug refers to.
        // We use the first element(the first dagPath of this emitter).
        //
        MPlug matrixPlug( thisNode, worldMatrixAttr );
        matrixPlug = matrixPlug.elementByLogicalIndex( 0 );

        // Get the value of the 'worldMatrix' attribute
        //
        MObject matrixObject;
        status = matrixPlug.getValue( matrixObject );
        if( !status )
        {
            status.perror("sweptEmitter::useRotation: get matrixObject");
            return ( direction );
        }

        MFnMatrixData worldMatrixData( matrixObject, &status );
        if( !status )
        {
            status.perror("sweptEmitter::useRotation: get worldMatrixData");
            return( direction );
        }

        MMatrix worldMatrix = worldMatrixData.matrix( &status );
        if( !status )
        {
            status.perror("sweptEmitter::useRotation: get worldMatrixData.matrix");
            return( direction );
        }

        rotatedVector = direction * worldMatrix;

        return( rotatedVector );
    }

    MStatus sweptEmitter::emitCountPerPoint
        (
            const MPlug &plug,
            MDataBlock &block,
            int length,                 // length of emitCountPP
            MIntArray &emitCountPP      // output: emitCount for each point
        )
    //
    //  Descriptions:
    //      Compute emitCount for each point where new particles come from.
    //
    {
        MStatus status;

        int plugIndex = plug.logicalIndex( &status );
        McheckErr(status, "ERROR in emitCountPerPoint: when plug.logicalIndex.\n");

        // Get rate and delta time.
        //
        double rate = rateValue( block );
        MTime dt = deltaTimeValue( plugIndex, block );

        // Compute emitCount for each point.
        //
        double dblCount = rate * dt.as( MTime::kSeconds );

        int intCount = (int)dblCount;
        for( int i = 0; i < length; i++ )
        {
            emitCountPP.append( intCount );
        }

        return( MS::kSuccess );
    }

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

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

        return status;
    }

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

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

        return status;
    }