void agg_renderer<T>::process(building_symbolizer const& sym,
                              mapnik::feature_impl & feature,
                              proj_transform const& prj_trans)
{
    typedef coord_transform<CoordTransform,geometry_type> path_type;
    typedef agg::renderer_base<agg::pixfmt_rgba32> ren_base;
    typedef agg::renderer_scanline_aa_solid<ren_base> renderer;

    agg::rendering_buffer buf(current_buffer_->raw_data(),width_,height_, width_ * 4);
    agg::pixfmt_rgba32 pixf(buf);
    ren_base renb(pixf);

    color const& fill_  = sym.get_fill();
    unsigned r=fill_.red();
    unsigned g=fill_.green();
    unsigned b=fill_.blue();
    unsigned a=fill_.alpha();
    renderer ren(renb);
    agg::scanline_u8 sl;

    ras_ptr->reset();
    ras_ptr->gamma(agg::gamma_power());

    double height = 0.0;
    expression_ptr height_expr = sym.height();
    if (height_expr)
    {
        value_type result = boost::apply_visitor(evaluate<Feature,value_type>(feature), *height_expr);
        height = result.to_double() * scale_factor_;
    }

    for (unsigned i=0;i<feature.num_geometries();++i)
    {
        geometry_type const& geom = feature.get_geometry(i);
        if (geom.size() > 2)
        {
            boost::scoped_ptr<geometry_type> frame(new geometry_type(LineString));
            boost::scoped_ptr<geometry_type> roof(new geometry_type(Polygon));
            std::deque<segment_t> face_segments;
            double x0 = 0;
            double y0 = 0;
            double x,y;
            geom.rewind(0);
            for (unsigned cm = geom.vertex(&x, &y); cm != SEG_END;
                 cm = geom.vertex(&x, &y))
            {
                if (cm == SEG_MOVETO)
                {
                    frame->move_to(x,y);
                }
                else if (cm == SEG_LINETO || cm == SEG_CLOSE)
                {
                    frame->line_to(x,y);
                    face_segments.push_back(segment_t(x0,y0,x,y));
                }
                x0 = x;
                y0 = y;
            }

            std::sort(face_segments.begin(),face_segments.end(), y_order);
            std::deque<segment_t>::const_iterator itr=face_segments.begin();
            std::deque<segment_t>::const_iterator end=face_segments.end();

            for (; itr!=end; ++itr)
            {
                boost::scoped_ptr<geometry_type> faces(new geometry_type(Polygon));
                faces->move_to(itr->get<0>(),itr->get<1>());
                faces->line_to(itr->get<2>(),itr->get<3>());
                faces->line_to(itr->get<2>(),itr->get<3>() + height);
                faces->line_to(itr->get<0>(),itr->get<1>() + height);

                path_type faces_path (t_,*faces,prj_trans);
                ras_ptr->add_path(faces_path);
                ren.color(agg::rgba8(int(r*0.8), int(g*0.8), int(b*0.8), int(a * sym.get_opacity())));
                agg::render_scanlines(*ras_ptr, sl, ren);
                ras_ptr->reset();
                //
                frame->move_to(itr->get<0>(),itr->get<1>());
                frame->line_to(itr->get<0>(),itr->get<1>()+height);

            }

            geom.rewind(0);
            for (unsigned cm = geom.vertex(&x, &y); cm != SEG_END;
                 cm = geom.vertex(&x, &y))
            {
                if (cm == SEG_MOVETO)
                {
                    frame->move_to(x,y+height);
                    roof->move_to(x,y+height);
                }
                else if (cm == SEG_LINETO || cm == SEG_CLOSE)
                {
                    frame->line_to(x,y+height);
                    roof->line_to(x,y+height);
                }
            }

            path_type path(t_,*frame,prj_trans);
            agg::conv_stroke<path_type> stroke(path);
            stroke.width(scale_factor_);
            ras_ptr->add_path(stroke);
            ren.color(agg::rgba8(int(r*0.8), int(g*0.8), int(b*0.8), int(a * sym.get_opacity())));
            agg::render_scanlines(*ras_ptr, sl, ren);
            ras_ptr->reset();

            path_type roof_path (t_,*roof,prj_trans);
            ras_ptr->add_path(roof_path);
            ren.color(agg::rgba8(r, g, b, int(a * sym.get_opacity())));
            agg::render_scanlines(*ras_ptr, sl, ren);

        }
    }
}
void render_building_symbolizer(mapnik::feature_impl &feature,
                                double height,
                                F1 face_func, F2 frame_func, F3 roof_func)
{
    for (auto const& geom : feature.paths())
    {
        if (geom.size() > 2)
        {
            const std::unique_ptr<geometry_type> frame(new geometry_type(geometry_type::types::LineString));
            const std::unique_ptr<geometry_type> roof(new geometry_type(geometry_type::types::Polygon));
            std::deque<segment_t> face_segments;
            double x0 = 0;
            double y0 = 0;
            double x,y;
            geom.rewind(0);
            for (unsigned cm = geom.vertex(&x, &y); cm != SEG_END;
                 cm = geom.vertex(&x, &y))
            {
                if (cm == SEG_MOVETO)
                {
                    frame->move_to(x,y);
                }
                else if (cm == SEG_LINETO)
                {
                    frame->line_to(x,y);
                    face_segments.push_back(segment_t(x0,y0,x,y));
                }
                else if (cm == SEG_CLOSE)
                {
                    frame->close_path();
                }
                x0 = x;
                y0 = y;
            }

            std::sort(face_segments.begin(),face_segments.end(), y_order);
            for (auto const& seg : face_segments)
            {
                const std::unique_ptr<geometry_type> faces(new geometry_type(geometry_type::types::Polygon));
                faces->move_to(std::get<0>(seg),std::get<1>(seg));
                faces->line_to(std::get<2>(seg),std::get<3>(seg));
                faces->line_to(std::get<2>(seg),std::get<3>(seg) + height);
                faces->line_to(std::get<0>(seg),std::get<1>(seg) + height);

                face_func(*faces);
                //
                frame->move_to(std::get<0>(seg),std::get<1>(seg));
                frame->line_to(std::get<0>(seg),std::get<1>(seg)+height);

            }

            geom.rewind(0);
            for (unsigned cm = geom.vertex(&x, &y); cm != SEG_END;
                 cm = geom.vertex(&x, &y))
            {
                if (cm == SEG_MOVETO)
                {
                    frame->move_to(x,y+height);
                    roof->move_to(x,y+height);
                }
                else if (cm == SEG_LINETO)
                {
                    frame->line_to(x,y+height);
                    roof->line_to(x,y+height);
                }
                else if (cm == SEG_CLOSE)
                {
                    frame->close_path();
                    roof->close_path();
                }
            }

            frame_func(*frame);
            roof_func(*roof);
        }
    }
}
void agg_renderer<T>::process(building_symbolizer const& sym,
                              Feature const& feature,
                              proj_transform const& prj_trans)
{
    typedef  coord_transform2<CoordTransform,geometry_type> path_type;
    typedef  coord_transform3<CoordTransform,geometry_type> path_type_roof;
    typedef agg::renderer_base<agg::pixfmt_rgba32_plain> ren_base;
    typedef agg::renderer_scanline_aa_solid<ren_base> renderer;

    agg::rendering_buffer buf(pixmap_.raw_data(),width_,height_, width_ * 4);
    agg::pixfmt_rgba32_plain pixf(buf);
    ren_base renb(pixf);

    color const& fill_  = sym.get_fill();
    unsigned r=fill_.red();
    unsigned g=fill_.green();
    unsigned b=fill_.blue();
    unsigned a=fill_.alpha();
    renderer ren(renb);
    agg::scanline_u8 sl;

    ras_ptr->reset();
    ras_ptr->gamma(agg::gamma_linear());
    
    double height = sym.height() * scale_factor_;
    
    for (unsigned i=0;i<feature.num_geometries();++i)
    {
        geometry_type const& geom = feature.get_geometry(i);
        if (geom.num_points() > 2)
        {
            boost::scoped_ptr<geometry_type> frame(new geometry_type(LineString));
            boost::scoped_ptr<geometry_type> roof(new geometry_type(Polygon));
            std::deque<segment_t> face_segments;
            double x0(0);
            double y0(0);
            unsigned cm = geom.vertex(&x0,&y0);
            for (unsigned j=1;j<geom.num_points();++j)
            {
                double x(0);
                double y(0);
                cm = geom.vertex(&x,&y);
                if (cm == SEG_MOVETO)
                {
                    frame->move_to(x,y);
                }
                else if (cm == SEG_LINETO)
                {
                    frame->line_to(x,y);
                    face_segments.push_back(segment_t(x0,y0,x,y));
                }
                
                x0 = x;
                y0 = y;
            }
            std::sort(face_segments.begin(),face_segments.end(), y_order);
            std::deque<segment_t>::const_iterator itr=face_segments.begin();
            for (;itr!=face_segments.end();++itr)
            {
                boost::scoped_ptr<geometry_type> faces(new geometry_type(Polygon));
                faces->move_to(itr->get<0>(),itr->get<1>());
                faces->line_to(itr->get<2>(),itr->get<3>());
                faces->line_to(itr->get<2>(),itr->get<3>() + height);
                faces->line_to(itr->get<0>(),itr->get<1>() + height);

                path_type faces_path (t_,*faces,prj_trans);
                ras_ptr->add_path(faces_path);
                ren.color(agg::rgba8(int(r*0.8), int(g*0.8), int(b*0.8), int(a * sym.get_opacity())));
                agg::render_scanlines(*ras_ptr, sl, ren);
                ras_ptr->reset();

                frame->move_to(itr->get<0>(),itr->get<1>());
                frame->line_to(itr->get<0>(),itr->get<1>()+height);
            }

            geom.rewind(0);
            for (unsigned j=0;j<geom.num_points();++j)
            {
                double x,y;
                unsigned cm = geom.vertex(&x,&y);
                if (cm == SEG_MOVETO)
                {
                    frame->move_to(x,y+height);
                    roof->move_to(x,y+height);
                }
                else if (cm == SEG_LINETO)
                {
                    frame->line_to(x,y+height);
                    roof->line_to(x,y+height);
                }
            }
            path_type path(t_,*frame,prj_trans);
            agg::conv_stroke<path_type> stroke(path);
            ras_ptr->add_path(stroke);
            ren.color(agg::rgba8(int(r*0.8), int(g*0.8), int(b*0.8), int(255 * sym.get_opacity())));
            agg::render_scanlines(*ras_ptr, sl, ren);
            ras_ptr->reset();

            path_type roof_path (t_,*roof,prj_trans);
            ras_ptr->add_path(roof_path);
            ren.color(agg::rgba8(r, g, b, int(a * sym.get_opacity())));
            agg::render_scanlines(*ras_ptr, sl, ren);
        }
    }
}