polyPrimitiveCmd/polyPrimitiveCmd.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 "polyPrimitiveTest".
//
// This plug-in creates the following types of polygon primitives at the origin:
//
//  1) Icosahedron
//  2) Dodecahedron
//  3) Tetrahedron
//  4) Cube
//  5) Octahedron
//  6) Plane
//  7) Cylinder
//  8) Truncated Icosahedron (soccer ball)
//
// It demonstrates the creation of polygonal data. Once it is loaded, executing
// "polyPrimitiveTest <primitive_number>" in the command window will cause a polygon
// to be created at the origin.          
//
// Usage:
//  polyPrimitiveTest <primitive_number>
//
// Related files:
//  polyPrimitiveCmd.mel
//
// Limitations:
//  Newly created primitives are always placed at origin
//
// Note:
//  Original implementation for OpenAlias in the jptPolyPrimitives plugin.
//

#include <math.h>

#include <maya/MArgList.h>
#include <maya/MDagModifier.h>
#include <maya/MDagPath.h>
#include <maya/MDoubleArray.h>
#include <maya/MFloatPoint.h>
#include <maya/MFloatPointArray.h>
#include <maya/MFnMesh.h>
#include <maya/MFnMeshData.h>
#include <maya/MFnPlugin.h>
#include <maya/MFnTypedAttribute.h>
#include <maya/MGlobal.h>
#include <maya/MIntArray.h>
#include <maya/MIOStream.h>
#include <maya/MPlug.h>
#include <maya/MPoint.h>
#include <maya/MPxCommand.h>
#include <maya/MString.h>

#ifndef M_PI
#define M_PI    3.14159265358979323846  /* pi */
#endif

// Macro for error checking
#define checkErr(stat,msg)          \
    if ( MS::kSuccess != stat ) {   \
        displayError(MString(msg) + ": " + stat.errorString());   \
        return stat;                \
    }

// Primitive face connect data //

static int tetra_gons[12] = {
    1,2,3,
    2,4,3,
    1,3,4,
    1,4,2
};

static int cube_gons[24] = {
    1,4,3,2,
    8,5,6,7,
    3,7,6,2,
    1,5,8,4,
    3,4,8,7,
    2,6,5,1
};

static int octa_gons[24] = {
    2,3,1,
    3,4,1,
    4,5,1,
    1,5,2,
    6,3,2,
    6,4,3,
    6,5,4,
    6,2,5
};

static int dodeca_gons[60] = {
    1,5,3,4,2,
    8,6,7,1,2,
    1,7,17,20,5,
    6,11,12,17,7,
    17,12,9,16,20,
    5,20,16,14,3,
    3,14,15,19,4,
    2,4,19,18,8,
    8,18,13,11,6,
    9,12,11,13,10,
    10,13,18,19,15,
    10,15,14,16,9
};

static int icosa_gons[60] = {
    2,10,1,
    1,11,2,
    1,8,7,
    1,7,11,
    1,10,8,
    5,2,6,
    10,2,5,
    2,11,6,
    4,9,3,
    3,12,4,
    5,6,3,
    3,9,5,
    6,12,3,
    7,8,4,
    4,12,7,
    4,8,9,
    5,9,10,
    6,11,12,
    7,12,11,
    8,10,9
};

static double trunc_icosa_vtxArray[][3] = {
    { 0.00000000, 0.00000000, 1.00000000 },
    { 0.39524780, 0.00000000, 0.91857395 },
    { -0.22278550, 0.32647698, 0.91857395 },
    { -0.14409696, -0.36804505, 0.91857395 },
    { 0.56771009, 0.32647698, 0.75572282 },
    { 0.49542801, -0.36804505, 0.78682468 },
    { -0.58966797, 0.28490989, 0.75572282 },
    { -0.05032380, 0.65295495, 0.75572282 },
    { 0.16209500, -0.59550930, 0.78682468 },
    { -0.51097943, -0.40961312, 0.75572282 },
    { 0.84035260, 0.28490989, 0.46112243 },
    { 0.34492458, 0.65295495, 0.67429775 },
    { 0.76807052, -0.40961312, 0.49222429 },
    { -0.64395201, 0.58569638, 0.49222429 },
    { -0.73376494, -0.08313546, 0.67429775 },
    { -0.31061900, 0.81316063, 0.49222429 },
    { 0.10140353, -0.86454163, 0.49222429 },
    { -0.57166993, -0.67864447, 0.46112243 },
    { 0.78606856, 0.58569638, 0.19762390 },
    { 0.94053281, -0.08313546, 0.32937316 },
    { 0.47987757, 0.81316063, 0.32937316 },
    { 0.70737904, -0.67864447, 0.19762390 },
    { -0.84233203, 0.51843879, 0.14730069 },
    { -0.93214496, -0.15039373, 0.32937316 },
    { -0.17566601, 0.97336729, 0.14730069 },
    { 0.37404603, -0.90610970, 0.19762390 },
    { -0.26547894, -0.90610970, 0.32937316 },
    { -0.83196474, -0.51843879, 0.19762390 },
    { 0.83196474, 0.51843879, -0.19762390 },
    { 0.98642507, -0.15039373, -0.06587463 },
    { 0.21958178, 0.97336729, 0.06587463 },
    { 0.84233203, -0.51843879, -0.14730069 },
    { -0.70737904, 0.67864447, -0.19762390 },
    { -0.98642507, 0.15039373, 0.06587463 },
    { -0.37404603, 0.90610970, -0.19762390 },
    { 0.17566601, -0.97336729, -0.14730069 },
    { -0.21958178, -0.97336729, -0.06587463 },
    { -0.78606856, -0.58569638, -0.19762390 },
    { 0.57166993, 0.67864447, -0.46112243 },
    { 0.93214496, 0.15039373, -0.32937316 },
    { 0.26547894, 0.90610970, -0.32937316 },
    { 0.64395201, -0.58569638, -0.49222429 },
    { -0.76807052, 0.40961312, -0.49222429 },
    { -0.94053281, 0.08313546, -0.32937316 },
    { -0.10140353, 0.86454163, -0.49222429 },
    { 0.31061900, -0.81316063, -0.49222429 },
    { -0.47987757, -0.81316063, -0.32937316 },
    { -0.84035260, -0.28490989, -0.46112243 },
    { 0.51097943, 0.40961312, -0.75572282 },
    { 0.73376494, 0.08313546, -0.67429775 },
    { 0.58966797, -0.28490989, -0.75572282 },
    { -0.49542801, 0.36804505, -0.78682468 },
    { -0.16209500, 0.59550930, -0.78682468 },
    { 0.05032380, -0.65295495, -0.75572282 },
    { -0.34492458, -0.65295495, -0.67429775 },
    { -0.56771009, -0.32647698, -0.75572282 },
    { 0.14409696, 0.36804505, -0.91857395 },
    { 0.22278550, -0.32647698, -0.91857395 },
    { -0.39524780, 0.00000000, -0.91857395 },
    { 0.00000000, 0.00000000, -1.00000000 }
};

static int trunc_icosa_faceCountArray[] =
{
    6, 6, 5, 6, 5,
    6, 5, 6, 6, 6,
    5, 6, 5, 6, 5,
    6, 6, 6, 5, 6,
    5, 5, 6, 6, 6,
    5, 6, 5, 6, 6,
    5, 6 
};

static int trunc_icosa_faceConnectArray[] = 
{
    0,1,4,11,7,2,
    0,2,6,14,9,3,
    3,8,5,1,0,
    5,12,19,10,4,1,
    7,15,13,6,2,
    9,17,26,16,8,3,
    4,10,18,20,11,
    5,8,16,25,21,12,
    6,13,22,33,23,14,
    7,11,20,30,24,15,
    9,14,23,27,17,
    19,29,39,28,18,10,
    21,31,29,19,12,
    13,15,24,34,32,22,
    26,36,35,25,16,
    27,37,46,36,26,17,
    28,38,40,30,20,18,
    21,25,35,45,41,31,
    22,32,42,43,33,
    33,43,47,37,27,23,
    24,30,40,44,34,
    39,49,48,38,28,
    29,31,41,50,49,39,
    32,34,44,52,51,42,
    35,36,46,54,53,45,
    47,55,54,46,37,
    48,56,52,44,40,38,
    41,45,53,57,50,
    51,58,55,47,43,42,
    48,49,50,57,59,56,
    51,52,56,59,58,
    53,54,55,58,59,57
};


// Class definition //

class polyPrimitive : public MPxCommand
{
public:
                 polyPrimitive() {};
         ~polyPrimitive() override; 

    MStatus      doIt( const MArgList& args ) override;
    MStatus      redoIt() override;
    MStatus      undoIt() override;

    inline bool  isUndoable() const override { return true; };
    static void* creator();

private:
    MStatus      assignShadingGroup(MObject transform, MString groupName);
    inline void  FILL( double x, double y, double z );
    void         create_icosa_points();
    void         create_dodecahedron();
    void         create_tetrahedron();
    void         create_cube();
    void         create_octahedron();
    void         create_truncated_icosahedron();
    void         createPlane();
    void         createCylinder();
    MStatus      createNodes();
    void         generatePrimitiveData();
    MStatus      renameNodes(MObject transform, MString baseName);
    MStatus      setMeshData(MObject transform, MObject dataWrapper);

    // What sort of shape we're making
    int shapeFlag;

    // Misc. primitive data
    //
    int num_verts;            // Number of vertices of polygon
    int num_faces;            // Number of faces on polygon
    int num_edges;            // Number of edges on polygon
    int edges_per_face;        // Number of edges (or verticies) per face
    int num_face_connects;    // Number of elements in face connect array
    int *p_gons;            // Pointer to static array of face connects
    MFloatPointArray iarr;
    MFloatPointArray pa;
    MIntArray faceCounts;
    MIntArray faceConnects;

    MDagModifier dagMod;
};



// Class implementation //

polyPrimitive::~polyPrimitive() {}

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

void polyPrimitive::FILL( double x, double y, double z )
{
    MFloatPoint pnt( (float)x, (float)y, (float)z );
    iarr.append( pnt );
}


// Primitive creation methods //

MStatus polyPrimitive::assignShadingGroup(MObject transform, MString groupName)
{
    MStatus st;

    // Get the name of the mesh node.
    //
    // We need to use an MFnDagNode rather than an MFnMesh because the mesh
    // is not fully realized at this point and would be rejected by MFnMesh.
    MFnDagNode  dagFn(transform);
    dagFn.setObject(dagFn.child(0));

    MString     meshName = dagFn.name();

    // Use the DAG modifier to put the mesh into a shading group
    MString     cmd("sets -e -fe ");
    cmd += groupName + " " + meshName;
    st = dagMod.commandToExecute(cmd);
    checkErr(st, "Could not add mesh to shading group");

    // Use the DAG modifier to select the new mesh.
    cmd = MString("select ") + meshName;
    st = dagMod.commandToExecute(cmd);
    checkErr(st, "Could not select new mesh");

    return st;
}

void polyPrimitive::create_icosa_points()
{
    double a = sqrt( ( 1.0 - sqrt( .2 ) ) / 2.0 );
    double b = sqrt( ( 1.0 + sqrt( .2 ) ) / 2.0 );
    double z = 0.0;

    FILL(b,a,z); FILL(b,-a,z); FILL(-b,-a,z); FILL(-b,a,z);
    FILL(0,-b,-a); FILL(0,-b,a); FILL(0,b,a); FILL(0,b,-a);
    FILL(-a,0,-b); FILL(a,0,-b); FILL(a,0,b); FILL(-a,0,b);
}

void polyPrimitive::create_dodecahedron()
{
    // Generated from icosahedron points.
    create_icosa_points();
    MFloatPoint my_info[12];
    int idx;
    for( idx = 0; idx < 12; idx++ ) {
        my_info[idx].x=iarr[idx].x;
        my_info[idx].y=iarr[idx].y;
        my_info[idx].z=iarr[idx].z;
    }

    iarr.clear();

    // now generate the dodecahedron points:
    double x1,y1,z1,x2,y2,z2,x3,y3,z3;
    double xf, yf, zf;
    double len;

    for( idx = 0; idx < 20; idx++ ) {
        x1 = my_info[ icosa_gons[3*idx]-1 ].x;
        y1 = my_info[ icosa_gons[3*idx]-1 ].y;
        z1 = my_info[ icosa_gons[3*idx]-1 ].z;

        x2 = my_info[ icosa_gons[3*idx + 1]-1 ].x;
        y2 = my_info[ icosa_gons[3*idx + 1]-1 ].y;
        z2 = my_info[ icosa_gons[3*idx + 1]-1 ].z;

        x3 = my_info[ icosa_gons[3*idx + 2]-1 ].x;
        y3 = my_info[ icosa_gons[3*idx + 2]-1 ].y;
        z3 = my_info[ icosa_gons[3*idx + 2]-1 ].z;

        // the docecahedron vertex is the average of these points.
        xf = (x1+x2+x3)/3.0;
        yf = (y1+y2+y3)/3.0;
        zf = (z1+z2+z3)/3.0;

        // One more transformation: scale this point so it lies on the
        // unit sphere...
        len = sqrt( xf*xf + yf*yf + zf*zf );
        xf /= len; yf /= len; zf /= len;

        FILL( xf, yf, zf );
    }
}

void polyPrimitive::create_tetrahedron( )
{
    // First, create the points:
    double sq = sqrt(3.0);
    FILL(0.0,0.0,1.0); FILL(sq/2.0,0.0,-.5);
    FILL(-sq/4.0,.75,-.5); FILL(-sq/4.0,-.75,-.5);
}

void polyPrimitive::create_cube( )
{
    // First, create the points:
    double a = sqrt( 1.0/3.0 );

    FILL(a,a,a); FILL(a,-a,a); FILL(-a,-a,a); FILL(-a,a,a);
    FILL(a,a,-a); FILL(a,-a,-a); FILL(-a,-a,-a); FILL(-a,a,-a);
}

void polyPrimitive::create_octahedron( )
{
    FILL(0.0,0.0,1.0); FILL(1.0,0.0,0.0);
    FILL(0.0,1.0,0.0); FILL(-1.0,0.0,0.0);
    FILL(0.0,-1.0,0.0); FILL(0.0,0.0,-1.0);
}

void polyPrimitive::create_truncated_icosahedron( )
{
    num_verts = 60;
    int idx;
    for ( idx = 0; idx < num_verts; idx++ )
    {
        FILL(trunc_icosa_vtxArray[idx][0], 
             trunc_icosa_vtxArray[idx][1],
             trunc_icosa_vtxArray[idx][2]);
    }

    num_faces = 32;
    for ( idx = 0; idx < num_faces; idx++ )
    {
        faceCounts.append( trunc_icosa_faceCountArray[idx] );
    }

    for ( idx = 0; idx < 180; idx++ )
    {
        faceConnects.append( trunc_icosa_faceConnectArray[idx] );
    }
}

void polyPrimitive::createPlane( )
{
    int w = 2;
    int h = 2;
    double size = 2.0;
    double hSize, wSize;

    // Initialize class data
    //
    num_verts      = 0;
    num_faces      = 0;
    edges_per_face = 4;

    if ( w < 1 ) w = 1;
    if ( h < 1 ) h = 1;
    if ( size < 0.0001 ) size = 1.0;

    wSize = size / w;
    hSize = size / h;

    // create vertices
    //
    double x, z;
    for ( z = -size/2.0; z <= size / 2.0; z += hSize )
    {
        for ( x = -size/2.0; x <= size/2.0; x += wSize )
        {
            FILL( x, 0, z );
            num_verts++;
        }
    }

    // create polys
    //
    int v0, v1, v2, v3;
    for ( int i = 0; i < h; i++ )
    {
        for ( int j = 0; j < w; j++ )
        {
            v0 = j + (w+1) * i;
            v1 = j + 1 + (w+1) * i;
            v2 = j + 1 + (w+1) * (i+1);
            v3 = j + (w+1) * (i+1);

            faceConnects.append( v0 );
            faceConnects.append( v3 );
            faceConnects.append( v2 );
            faceConnects.append( v1 );
            num_faces++;
            faceCounts.append( edges_per_face );
        }
    }

    num_face_connects = num_faces * edges_per_face;
    num_edges = num_face_connects / 2;
}

void polyPrimitive::createCylinder()
{
    double r        = 1.0;
    double height   = 2.0;
    int sides       = 8;
    int sections    = 2;

    // Initialize class data
    //
    num_verts       = 0;
    num_faces       = 0;
    edges_per_face  = 0;


    if ( sides < 3 ) sides = 3;
    if ( sections < 1 ) sections = 1;
    if ( height <= 0 ) height = 1.0;
    if ( r <= 0 ) r = 1.0;

    // create verts
    //
    double angle, deg = 360.0 / (double) sides;
    double hSize = height / (double) sections;
    double x, z, y = height / 2.0;
    int i,j;

    for ( i = 0; i <= sections; i++ )
    {
        for ( j = sides - 1; j >= 0; j-- )
        {
            angle = deg * j / 180.0 * M_PI;
            x = cos( angle );
            z = sin( angle );
            FILL( x, y, z );
            num_verts++;
        } // for j
        
        y -= hSize;
    } // for i
    

    // create polys
    //
    for ( i = 0; i < sides; i++ )
    {
        faceConnects.append( i );
        edges_per_face++;
    }
    num_faces++;
    faceCounts.append( edges_per_face );
    edges_per_face = 0;
        
    for ( i = sides-1; i >= 0; i-- )
    {
        faceConnects.append( i + sides * sections );
        edges_per_face++;
    }
    num_faces++;
    faceCounts.append( edges_per_face );
    edges_per_face = 0;

    int v0, v1, v2, v3;
    for ( i = 0; i < sections; i++ )
    {
        for ( j = 0; j < sides; j++ )
        {
            if ( j == 0 )    // use last vtx on this section
            {
                v0 = sides - 1 + sides * i;
                v3 = sides - 1 + sides * (i+1);
            }
            else            // use prev vtx
            {
                v0 = j - 1 + sides * i;
                v3 = j - 1 + sides * (i+1);
            }
            v1 = j + sides * i;
            v2 = j + sides * (i+1);
            
            faceConnects.append( v0 );
            faceConnects.append( v3 );
            faceConnects.append( v2 );
            faceConnects.append( v1 );
            num_faces++;
            faceCounts.append( 4 );
        } // for j
    } // for i

    num_face_connects = faceConnects.length();
    num_edges = num_face_connects/2;
}


void polyPrimitive::generatePrimitiveData()
{
    // Decide which type of primitive to create
    //
    iarr.clear();
    faceCounts.clear();
    faceConnects.clear();

    switch( shapeFlag ) {
        case 1:
        default:
            create_icosa_points();
            num_verts         = 12;
            num_faces         = 20;
            edges_per_face    =  3;
            p_gons = icosa_gons;
            break;
        case 2:
            create_dodecahedron();
            num_verts         = 20;
            num_faces         = 12;
            edges_per_face    =  5;
            p_gons = dodeca_gons;
            break;
        case 3:
            create_tetrahedron();
            num_verts         = 4;
            num_faces         = 4;
            edges_per_face    = 3;
            p_gons = tetra_gons;
            break;
        case 4:
            create_cube();
            num_verts         = 8;
            num_faces         = 6;
            edges_per_face    = 4;
            p_gons = cube_gons;
            break;
        case 5:
            create_octahedron();
            num_verts         = 6;
            num_faces         = 8;
            edges_per_face    = 3;
            p_gons = octa_gons;
            break;
        case 6:
            createPlane();
            p_gons = NULL;
            break;
        case 7:
            createCylinder();
            p_gons = NULL;
            break;
        case 8:
            create_truncated_icosahedron();
            p_gons = NULL;
            break;
    }
    
    // Construct the point array
    //
    pa.clear();
    int i;
    for ( i=0; i<num_verts; i++ )
        pa.append( iarr[i] );

    // If we are using polygon data then set up the face connect array
    // here. Otherwise, the create function will do it.
    //
    if ( NULL != p_gons ) {
        num_face_connects = num_faces * edges_per_face;
        num_edges = num_face_connects/2;

        for ( i=0; i<num_faces; i++ )
            faceCounts.append( edges_per_face );

        for ( i=0; i<(num_faces*edges_per_face); i++ )
            faceConnects.append( p_gons[i]-1 );
    }
}

MStatus polyPrimitive::createNodes()
{
    MStatus  st;

    // Generate the raw data for the requested primitive.
    generatePrimitiveData();

    // Create a mesh data wrapper to hold the new geometry.
    MFnMeshData    dataFn;
    MObject        dataWrapper = dataFn.create();

    // Create the mesh geometry and put it into the wrapper.
    MFnMesh        meshFn;
    MObject        dataObj = meshFn.create(
                                num_verts,
                                num_faces,
                                pa,
                                faceCounts,
                                faceConnects,
                                dataWrapper,
                                &st
                            );
    checkErr(st, "Could not create mesh data");

    // Use the DAG modifier to create an empty mesh node and its parent
    // transform.
    MObject transform = dagMod.createNode("mesh", MObject::kNullObj, &st);
    checkErr(st, "Could not create empty mesh" );

    // Commit the creation so that the transform and its child will be
    // valid below.
    st = dagMod.doIt();
    checkErr(st, "Could not commit creation of empty mesh");

    // At the moment we have a transform named something like 'transform1'
    // and a mesh named something like 'polySurfaceShape1'. Let's tidy that
    // up by renaming them as 'pPrimitive#' and 'pPrimitiveShape#', where
    // '#' is a number to ensure uniqueness.
    st = renameNodes(transform, "pPrimitive");
    if (!st) return st;

    // Commit the rename so that assignShadingGroup() can get the new name.
    st = dagMod.doIt();
    checkErr(st, "Could not commit renaming of nodes");

    // Assign the mesh to a shading group.
    st = assignShadingGroup(transform, "initialShadingGroup");
    if (!st) return st;

    // Commit the changes.
    st = dagMod.doIt();
    checkErr(st, "Could not commit final changes");

    // Set the mesh node to use the geometry we created for it.
    st = setMeshData(transform, dataWrapper);
    if (!st) return st;

    return st;
}


// Rename a transform and its shape so that they have the following names:
//
//      <baseName>#
//      <baseName>Shape#
//
// where <baseName> is the string provided in the 'baseName' parameter and
// '#' is an integer value which ensures the names are unique within the
// scene.
MStatus polyPrimitive::renameNodes(MObject transform, MString baseName)
{
    MStatus st;

    //  Rename the transform to something we know no node will be using.
    st = dagMod.renameNode(transform, "polyPrimitiveCmdTemp");
    checkErr(st, "Could not rename transform node to temp name");

    //  Rename the mesh to the same thing but with 'Shape' on the end.
    MFnDagNode    dagFn(transform);

    st = dagMod.renameNode(dagFn.child(0), "polyPrimitiveCmdTempShape");
    checkErr(st, "Could not rename mesh node to temp name");

    //  Now that they are in the 'something/somethingShape' format, any
    //  changes we make to the name of the transform will automatically be
    //  propagated to the shape as well.
    //
    //  Maya will replace the '#' in the string below with a number which
    //  ensures uniqueness.
    MString  transformName = baseName + "#";
    st = dagMod.renameNode(transform, transformName);
    checkErr(st, "Could not rename transform node to final name");

    return st;
}


MStatus polyPrimitive::setMeshData(MObject transform, MObject dataWrapper)
{
    MStatus st;

    // Get the mesh node.
    MFnDagNode  dagFn(transform);
    MObject     mesh = dagFn.child(0);

    // The mesh node has two geometry inputs: 'inMesh' and 'cachedInMesh'.
    // 'inMesh' is only used when it has an incoming connection, otherwise
    // 'cachedInMesh' is used. Unfortunately, the docs say that 'cachedInMesh'
    // is for internal use only and that changing it may render Maya
    // unstable.
    //
    // To get around that, we do the little dance below...

    // Use a temporary MDagModifier to create a temporary mesh attribute on
    // the node.
    MFnTypedAttribute  tAttr;
    MObject            tempAttr = tAttr.create("tempMesh", "tmpm", MFnData::kMesh);
    MDagModifier       tempMod;

    st = tempMod.addAttribute(mesh, tempAttr);
    checkErr(st, "Could not add 'tempMesh' attribute");

    st = tempMod.doIt();
    checkErr(st, "Could not commit addition of 'tempMesh' attribute");

    // Set the geometry data onto the temp attribute.
    dagFn.setObject(mesh);

    MPlug  tempPlug = dagFn.findPlug(tempAttr, true);

    st = tempPlug.setValue(dataWrapper);
    checkErr(st, "Could not set mesh geometry" );

    // Use the temporary MDagModifier to connect the temp attribute to the
    // node's 'inMesh'.
    MPlug  inMeshPlug = dagFn.findPlug("inMesh", true);
    
    st = tempMod.connect(tempPlug, inMeshPlug);
    checkErr(st, "Could not connect 'tempMesh' to 'inMesh'");

    st = tempMod.doIt();
    checkErr(st, "Could not commit connection of 'tempMesh' to 'inMesh'");

    // Force the mesh to update by grabbing its output geometry.
    dagFn.findPlug("outMesh", true).asMObject();

    // Undo the temporary modifier.
    st = tempMod.undoIt();
    checkErr(st, "Could not undo 'tempMesh' attribute");

    return st;
}


MStatus polyPrimitive::doIt( const MArgList& args )
{
    MStatus  st;

    // Command line argument specifies type of primitive to create
    //
    shapeFlag = 1;
    if ( args.length() > 0 )
        shapeFlag = args.asInt(0);

    // Create the mesh and its transform.
    st = createNodes();

    // If the creation failed, clean up any partial changes made.
    if (!st) {
        dagMod.undoIt();
    }

    return st;
}

MStatus polyPrimitive::redoIt()
{        
    return dagMod.doIt();
}

MStatus polyPrimitive::undoIt()
{
    return dagMod.undoIt();
}

MStatus initializePlugin( MObject obj )
{
    MStatus   status;
    MFnPlugin plugin( obj, PLUGIN_COMPANY, "4.0", "Any");

    status = plugin.registerCommand( "polyPrimitiveTest", polyPrimitive::creator );
    if (!status) {
        status.perror("registerCommand");
        return status;
    }
    
    status = plugin.registerUI("polyPrimitiveCreateUI", "polyPrimitiveDeleteUI");
    if (!status) {
        status.perror("registerUI");
        return status;
    }

    return status;
}

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

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

    return status;
}