simpleEmitter/simpleEmitter.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.
// ==========================================================================
//+

// DESCRIPTION:
// 
// Produces the dependency graph node "simpleEmitter".
//
// This node is an example of a particle emitter that
// emits in a direction from a single position.
//
// The example MEL script "simpleEmitter.mel" shows how to create the node
// and appropriate connections to correctly establish a user defined particle emitter. 
//

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

#include "simpleEmitter.h"

#include <maya/MVectorArray.h>
#include <maya/MDoubleArray.h>
#include <maya/MIntArray.h>
#include <maya/MMatrix.h>
#include <maya/MArrayDataBuilder.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 simpleEmitter::id( 0x80014 );


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


simpleEmitter::~simpleEmitter()
{
}


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


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


MStatus simpleEmitter::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");

    // Create the data and apply the function set,
    // particle array initialized to length zero, 
    // fnOutput.clear()
    //
    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 input position and velocity arrays where new particles are from,
    // also known as the owner. An owner is determined if connections exist
    // to the emitter node from a shape such as nurbs, polymesh, curve, 
    // or a lattice shape.
    //

    // Get a single position from world transform
    //
    MVectorArray inPosAry;
    inPosAry.clear();

    MPoint worldPos(0.0, 0.0, 0.0);
    status = getWorldPosition( worldPos );
    MVector worldV;
    worldV[0] = worldPos[0];
    worldV[1] = worldPos[1];
    worldV[2] = worldPos[2];
    inPosAry.append( worldV );

    // Create a single velocity
    MVectorArray inVelAry;
    inVelAry.clear();
    MVector velocity(0,0,0);
    inVelAry.append( velocity );

    // 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 );
    }

    // Compute and store an emission rate
    //
    MIntArray emitCountPP;
    emitCountPP.clear();

    int plugIndex = plug.logicalIndex( &status );

    // Get rate and delta time.
    //
    double rate = rateValue( block );
    MTime dtRate = deltaTimeValue( plugIndex, block );
    double dblCount = rate * dtRate.as( MTime::kSeconds );
    int intCount = (int)dblCount;
    emitCountPP.append( intCount );


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

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

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

    // Rotate the direction attribute by world transform
    MVector rotatedV = useRotation ( dirV );

    // Start emitting particles.
    //
    emit( inPosAry, inVelAry, emitCountPP,
            dt, speed, inheritFactor, rotatedV, fnOutPos, fnOutVel, fnOutTime );

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

    return( MS::kSuccess );
}


void simpleEmitter::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
        MDoubleArray &outTimeAry        // holding new particles emitted time
    )
//
//  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 );
            outTimeAry.append( alpha );
        }
    }
}


MStatus simpleEmitter::getWorldPosition( MPoint &point )
//
//  Descriptions:
//      get the emitter position in the world space.
//      The position value is from inherited attribute, aWorldMatrix.
//
{
    MStatus status;

    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("simpleEmitter::getWorldPosition: get matrixObject");
        return( status );
    }

    MFnMatrixData worldMatrixData( matrixObject, &status );
    if( !status )
    {
        status.perror("simpleEmitter::getWorldPosition: get worldMatrixData");
        return( status );
    }

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

    // assign the translate to the given vector.
    //
    point[0] = worldMatrix( 3, 0 );
    point[1] = worldMatrix( 3, 1 );
    point[2] = worldMatrix( 3, 2 );

    return( status );
}


MStatus simpleEmitter::getWorldPosition( MDataBlock& block, MPoint &point )
//
//  Descriptions:
//      Find the emitter position in the world space.
//
{
    MStatus status;

    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 );
    MDataHandle hWMatrix = block.inputValue( matrixPlug, &status );

    McheckErr(status, "ERROR getting hWMatrix from dataBlock.\n");

    if( status == MS::kSuccess )
    {
        MMatrix wMatrix = hWMatrix.asMatrix();
        point[0] = wMatrix(3, 0);
        point[1] = wMatrix(3, 1);
        point[2] = wMatrix(3, 2);
    }
    return( status );
}

MVector simpleEmitter::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("simpleEmitter::getWorldPosition: get matrixObject");
        return ( direction );
    }

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

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

    rotatedVector = direction * worldMatrix;

    return( rotatedVector );
}

#define TORUS_PI 3.14159265
#define TORUS_2PI 2*TORUS_PI
#define EDGES 30
#define SEGMENTS 20

//
//  Descriptions:
//      Draw a set of rings to symbolie the field. This does not override default icon, you can do that by implementing the iconBitmap() function
//

void simpleEmitter::draw( M3dView& view, const MDagPath& path, M3dView::DisplayStyle style, M3dView:: DisplayStatus )
{
    view.beginGL();
    for (int j = 0; j < SEGMENTS; j++ )
    {
        glPushMatrix();
        glRotatef( GLfloat(360 * j / SEGMENTS), 0.0, 1.0, 0.0 );
        glTranslatef( 1.5, 0.0, 0.0 );

        for (int i = 0; i < EDGES; i++ )
        {
            glBegin(GL_LINE_STRIP);
            float p0 = float( TORUS_2PI * i / EDGES );
            float p1 = float( TORUS_2PI * (i+1) / EDGES );
            glVertex2f( cos(p0), sin(p0) );
            glVertex2f( cos(p1), sin(p1) );
            glEnd();
        }
        glPopMatrix();
    }
    view.endGL ();
}


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

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

    return status;
}

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

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

    return status;
}