OpenSceneGraph/src/osgPlugins/gles/EdgeIndexFunctor

/* -*-c++-*- OpenSceneGraph - Copyright (C) Cedric Pinson
 *
 * This application is open source and may be redistributed and/or modified
 * freely and without restriction, both in commercial and non commercial
 * applications, as long as this copyright notice is maintained.
 *
 * This application 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.
 *
 */

#ifndef EDGE_INDEX_FUNCTOR_H
#define EDGE_INDEX_FUNCTOR_H

#include <osg/PrimitiveSet>
#include <osg/Array>


template<class T>
class EdgeIndexFunctor : public osg::PrimitiveIndexFunctor, public T
{
public:
    virtual void setVertexArray(unsigned int,const osg::Vec2*)
    {}

    virtual void setVertexArray(unsigned int ,const osg::Vec3* )
    {}

    virtual void setVertexArray(unsigned int,const osg::Vec4* )
    {}

    virtual void setVertexArray(unsigned int,const osg::Vec2d*)
    {}

    virtual void setVertexArray(unsigned int ,const osg::Vec3d* )
    {}

    virtual void setVertexArray(unsigned int,const osg::Vec4d* )
    {}

    virtual void begin(GLenum mode) {
        _modeCache = mode;
        _indexCache.clear();
    }

    virtual void vertex(unsigned int vert) {
        _indexCache.push_back(vert);
    }

    virtual void end() {
        if (!_indexCache.empty()) {
            drawElements(_modeCache, _indexCache.size(), &_indexCache.front());
        }
    }

    virtual void drawArrays(GLenum mode, GLint first, GLsizei count) {
        switch(mode)
        {
        case(GL_TRIANGLES):
        {
            unsigned int pos=first;
            for(GLsizei i = 2 ; i < count ; i += 3, pos += 3)
            {
                this->operator()(pos,   pos+1);
                this->operator()(pos+1, pos+2);
                this->operator()(pos+2, pos);
            }
            break;
        }
        case(GL_TRIANGLE_STRIP):
        {
            unsigned int pos=first;
            for(GLsizei i = 2 ; i < count ; ++ i, ++ pos)
            {
                if ((i % 2)) {
                    this->operator()(pos,   pos+2);
                    this->operator()(pos+2, pos+1);
                    this->operator()(pos+1, pos);
                } else {
                    this->operator()(pos,   pos+1);
                    this->operator()(pos+1, pos+2);
                    this->operator()(pos,   pos+2);
                }
            }
            break;
        }
        case(GL_QUADS):
        {
            unsigned int pos=first;
            for(GLsizei i = 3 ; i < count ; i += 4, pos += 4)
            {
                this->operator()(pos,   pos+1);
                this->operator()(pos+1, pos+2);
                this->operator()(pos+2, pos+3);
                this->operator()(pos+3, pos);
            }
            break;
        }
        case(GL_QUAD_STRIP):
        {
            unsigned int pos=first;
            for(GLsizei i = 3 ; i < count ; i += 2, pos += 2)
            {
                this->operator()(pos,   pos+1);
                this->operator()(pos+1, pos+3);
                this->operator()(pos+2, pos+3);
                this->operator()(pos+2, pos);
            }
            break;
        }
        case(GL_POLYGON): // treat polygons as GL_TRIANGLE_FAN
        case(GL_TRIANGLE_FAN):
        {
            unsigned int pos=first+1;
            for(GLsizei i = 2 ; i < count ; ++ i, ++ pos) {
                this->operator()(pos, pos+1);
            }
            break;
        }
        case(GL_LINES):
        {
            unsigned int pos=first;
            for(GLsizei i = 0 ; i < count ; i += 2, pos += 2) {
                this->operator()(pos, pos+1);
            }
        }
        break;
        case(GL_LINE_STRIP):
        {
            unsigned int pos=first;
            for(GLsizei i = 0 ; i < count - 1 ; i += 1, pos += 1) {
                this->operator()(pos, pos+1);
            }
        }
        break;
        case(GL_LINE_LOOP):
        {
            unsigned int pos=first;
            for(GLsizei i = 0 ; i < count - 1; i += 1, pos += 1) {
                this->operator()(pos, pos+1);
            }
            this->operator()(pos, first);
        }
        break;
        case(GL_POINTS):
            break;
        default:
            // can't be converted into to edges.
            break;
        }
    }

    template<typename I>
    void drawElements(GLenum mode, GLsizei count, const I* indices) {
        if (indices == 0 || count == 0) return;

        switch(mode)
        {
        case(GL_TRIANGLES):
        {
            const I* ilast = &indices[count];
            for(const I* iptr = indices ; iptr < ilast ; iptr += 3) {
                this->operator()(*iptr,     *(iptr+1));
                this->operator()(*(iptr+1), *(iptr+2));
                this->operator()(*iptr,     *(iptr+2));
            }
            break;
        }
        case(GL_TRIANGLE_STRIP):
        {
            const I* iptr = indices;
            for(GLsizei i = 2 ; i < count ; ++ i, ++ iptr) {
                I v0 = *(iptr),
                  v1 = *(iptr + 1),
                  v2 = *(iptr + 2);

                // when merging strips we create degenerate triangles and add
                // non existing edges that should be filtered
                if(v0 == v1 || v0 == v2 || v1 == v2) continue;

                if ((i % 2)) {
                    this->operator()(v0, v2);
                    this->operator()(v2, v1);
                    this->operator()(v0, v1);
                } else {
                    this->operator()(v0, v1);
                    this->operator()(v1, v2);
                    this->operator()(v0, v2);
                }
            }
            break;
        }
        case(GL_QUADS):
        {
            const I* iptr = indices;
            for(GLsizei i = 3 ; i < count ; i += 4, iptr += 4) {
                this->operator()(*(iptr),   *(iptr+1));
                this->operator()(*(iptr+1), *(iptr+2));
                this->operator()(*(iptr+2), *(iptr+3) );
                this->operator()(*(iptr),   *(iptr+3) );
            }
            break;
        }
        case(GL_QUAD_STRIP):
        {
            const I* iptr = indices;
            for(GLsizei i = 3 ; i < count ; i += 2, iptr += 2) {
                this->operator()(*(iptr),   *(iptr+1));
                this->operator()(*(iptr+3), *(iptr+1));
                this->operator()(*(iptr+2), *(iptr+3));
                this->operator()(*(iptr),   *(iptr+2));
            }
            break;
        }
        case(GL_POLYGON): // treat polygons as GL_TRIANGLE_FAN
        case(GL_TRIANGLE_FAN):
        {
            const I* iptr = indices;
            ++iptr;
            for(GLsizei i = 2 ; i < count ; ++ i, ++ iptr) {
                this->operator()(*(iptr), *(iptr+1));
            }
            break;
        }
        case(GL_LINES):
        {
            const I* iptr = indices;
            for(GLsizei i = 0 ; i < count - 1 ; i += 2, iptr += 2) {
                this->operator()(*iptr, *(iptr+1));
            }
        }
        break;
        case(GL_LINE_STRIP):
        {
            const I* iptr = indices;
            for(GLsizei i = 0 ; i < count - 1 ; i += 1, iptr += 1) {
                this->operator()(*iptr, *(iptr+1));
            }
        }
        break;
        case(GL_LINE_LOOP):
        {
            const I* iptr = indices;
            I first = *iptr;
            for(GLsizei i = 0 ; i < count - 1 ; i += 1, iptr += 1) {
                this->operator()(*iptr, *(iptr+1));
            }
            this->operator()(*iptr, first);
        }
        break;
        case(GL_POINTS):
            break;
        default:
            // can't be converted into to edge lines
            break;
        }
    }

    virtual void drawElements(GLenum mode, GLsizei count, const GLubyte* indices) {
        drawElements<GLubyte>(mode, count, indices);
    }

    virtual void drawElements(GLenum mode, GLsizei count, const GLushort* indices) {
        drawElements<GLushort>(mode, count, indices);
    }

    virtual void drawElements(GLenum mode, GLsizei count, const GLuint* indices) {
        drawElements<GLuint>(mode, count, indices);
    }


    GLenum                      _modeCache;
    std::vector<GLuint>         _indexCache;
};

#endif