Tessellator

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSGUTIL_Tessellator
#define OSGUTIL_Tessellator

#include <osg/Geometry>

#include <osgUtil/Export>

#include <osg/GLU>

#include <vector>

#ifndef CALLBACK
    /* Win32 calling conventions. (or a least thats what the GLUT example tess.c uses.)*/
    #define CALLBACK
#endif

namespace osgUtil {

/** Originally a simple class for tessellating a single polygon boundary.
  * Using old style glu tessellation functions for portability.
  * Upgraded Jan 2004 to use the modern glu tessellation functions.*/

class OSGUTIL_EXPORT Tessellator : public osg::Referenced
{
    public:
   
        Tessellator();
        ~Tessellator();

        /** The winding rule, see red book ch 11. */
        enum WindingType{
            TESS_WINDING_ODD          = GLU_TESS_WINDING_ODD,
            TESS_WINDING_NONZERO      = GLU_TESS_WINDING_NONZERO,
            TESS_WINDING_POSITIVE     = GLU_TESS_WINDING_POSITIVE,
            TESS_WINDING_NEGATIVE     = GLU_TESS_WINDING_NEGATIVE,
            TESS_WINDING_ABS_GEQ_TWO  = GLU_TESS_WINDING_ABS_GEQ_TWO
        } ;

        /** we interpret all contours in the geometry as a single set to be tessellated or
         * each separate drawable's contours needs to be tessellated. */
        enum TessellationType {
            TESS_TYPE_GEOMETRY, // tessellate everything in the geometry object
            TESS_TYPE_DRAWABLE, // tessellate each polygon, triangles & quads drawables in geometry separately
            TESS_TYPE_POLYGONS // tessellate ONLY polygon drawables in geometry separately
        };

        /** Set and get tessellation request boundary only on/off */
        void setBoundaryOnly (const bool tt) { _boundaryOnly=tt;}
        inline bool getBoundaryOnly ( ) { return _boundaryOnly;}

        /** Set and get tessellation windong rule */
        void setWindingType (const WindingType wt) { _wtype=wt;}
        inline WindingType getWindingType ( ) { return _wtype;}

        /** Set and get tessellation type */
        void setTessellationType (const TessellationType tt) { _ttype=tt;}
        inline TessellationType getTessellationType ( ) { return _ttype;}

        /** Change the contours lists of the geometry into tessellated primitives (the
          * list of primitives in the original geometry is stored in the Tessellator for
          * possible re-use. 
          * The name remains retessellatePolygons although it now handles trifans, strips, quads etc.
          * as well as Polygons so as to not break old codes relying on this function name. */
        void retessellatePolygons(osg::Geometry &cxgeom);

        /** Define the normal to the tessellated polygon - this provides a hint how to
         *  tessellate the contours; see gluTessNormal in red book or man pages.
         *  GWM July 2005. Can improve teselation
         *  "For example, if you know that all polygons lie in the x-y plane, 
         *   call gluTessNormal(tess, 0.0, 0.0, 1.0) before rendering any polygons."
         */
        void setTessellationNormal(const osg::Vec3 norm) { tessNormal=norm;}

        osg::Geometry::PrimitiveSetList  getContours() { return _Contours;}

        typedef std::vector<osg::Vec3*> VertexPointList;
        
        struct Prim : public osg::Referenced
        {
            Prim(GLenum mode):_mode(mode) {}
        
            typedef std::vector<osg::Vec3*> VecList;

            GLenum  _mode;
            VecList _vertices;
        };
        
        void beginTessellation();
        
        void beginContour();
        void addVertex(osg::Vec3* vertex);
        void endContour();
        
        void endTessellation();

        typedef std::vector< osg::ref_ptr<Prim> > PrimList;
        
        PrimList& getPrimList() { return _primList; }        
        
        void reset();
        
    protected:

        /** remove unused parts of the array, eg for wehn retessellating
         * tessellation can introduce extra vertices for concave or crossing boundaries,
         * these will leak memory if not removed when retessellating. */
        void reduceArray(osg::Array * cold, const unsigned int nnu);

        void collectTessellation(osg::Geometry &cxgeom, unsigned int originalIndex);
        
        typedef std::map<osg::Vec3*,unsigned int> VertexPtrToIndexMap;
        void addContour(GLenum  mode, unsigned int first, unsigned int last, osg::Vec3Array* vertices);
        void addContour(osg::PrimitiveSet* primitive, osg::Vec3Array* vertices);
        void handleNewVertices(osg::Geometry& geom,VertexPtrToIndexMap &vertexPtrToIndexMap);

        void begin(GLenum mode);
        void vertex(osg::Vec3* vertex);
        void combine(osg::Vec3* vertex,void* vertex_data[4],GLfloat weight[4]);
        void end();
        void error(GLenum errorCode);

    
        static void CALLBACK beginCallback(GLenum which, void* userData);
        static void CALLBACK vertexCallback(GLvoid *data, void* userData);
        static void CALLBACK combineCallback(GLdouble coords[3], void* vertex_data[4],
                              GLfloat weight[4], void** outData,
                              void* useData);
        static void CALLBACK endCallback(void* userData);
        static void CALLBACK errorCallback(GLenum errorCode, void* userData);
        
        
        struct Vec3d
        {
            double _v[3];
        };


        struct NewVertex
        {
        
            NewVertex():
                _vpos(0),
                _f1(0),
                _v1(0),
                _f2(0),
                _v2(0),
                _f3(0),
                _v3(0),
                _f4(0),
                _v4(0) {}
            
            NewVertex(const NewVertex& nv):
                _vpos(nv._vpos),
                _f1(nv._f1),
                _v1(nv._v1),
                _f2(nv._f2),
                _v2(nv._v2),
                _f3(nv._f3),
                _v3(nv._v3),
                _f4(nv._f4),
                _v4(nv._v4) {}

            NewVertex(osg::Vec3* vx,
                      float f1,osg::Vec3* v1,
                      float f2,osg::Vec3* v2,
                      float f3,osg::Vec3* v3,
                      float f4,osg::Vec3* v4):
                _vpos(vx),
                _f1(f1),
                _v1(v1),
                _f2(f2),
                _v2(v2),
                _f3(f3),
                _v3(v3),
                _f4(f4),
                _v4(v4) {}

            osg::Vec3  *_vpos; // added gwm Jan 2004 the vertex coords s.t. NewVertex can be used in a std::vector
        
            float       _f1;
            osg::Vec3*  _v1;

            float       _f2;
            osg::Vec3*  _v2;

            float       _f3;
            osg::Vec3*  _v3;

            float       _f4;
            osg::Vec3*  _v4;
            
        };
        
        //change NewVertexList from std::map<osg::Vec3*,NewVertex> NewVertexList;
        // because this has undefined order of insertion for new vertices. 
        // which occasionally corrupted the texture mapping.
        typedef std::vector<NewVertex> NewVertexList;
        typedef std::vector<Vec3d*> Vec3dList;

        osg::GLUtesselator*  _tobj;

        PrimList        _primList;
        Vec3dList       _coordData;
        NewVertexList   _newVertexList;
        GLenum          _errorCode;

        /** winding rule, which parts will become solid */
        WindingType _wtype; 

        /** tessellation rule, which parts will become solid */
        TessellationType _ttype;

        bool _boundaryOnly; // see gluTessProperty - if true: make the boundary edges only.

        /** number of vertices that are part of the 'original' set of contours */
        unsigned int _numberVerts;

        /** List of primitives that define the contours */
        osg::Geometry::PrimitiveSetList                _Contours;

        /** count number of primitives in a geometry to get right no. of norms/colurs etc for per_primitive attributes. */
        unsigned int _index;

        /** the gluTessNormal for tessellation hint */
        osg::Vec3 tessNormal;

        /** count of number of extra primitives added */
        unsigned int _extraPrimitives;
};

}

#endif