agg/inc/agg_span_gouraud.h

   1 //----------------------------------------------------------------------------
   2 // Anti-Grain Geometry - Version 2.3
   3 // Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
   4 //
   5 // Permission to copy, use, modify, sell and distribute this software
   6 // is granted provided this copyright notice appears in all copies.
   7 // This software is provided "as is" without express or implied
   8 // warranty, and with no claim as to its suitability for any purpose.
   9 //
  10 //----------------------------------------------------------------------------
  11 // Contact: mcseem@antigrain.com
  12 //          mcseemagg@yahoo.com
  13 //          http://www.antigrain.com
  14 //----------------------------------------------------------------------------
  15
  16 #ifndef AGG_SPAN_GOURAUD_INCLUDED
  17 #define AGG_SPAN_GOURAUD_INCLUDED
  18
  19 #include "agg_basics.h"
  20 #include "agg_math.h"
  21 #include "agg_span_generator.h"
  22
  23 namespace agg
  24 {
  25
  26     //============================================================span_gouraud
  27     template<class ColorT, class Allocator>
  28     class span_gouraud : public span_generator<ColorT, Allocator>
  29     {
  30     public:
  31         typedef ColorT color_type;
  32         typedef Allocator alloc_type;
  33
  34         struct coord_type
  35         {
  36             double x;
  37             double y;
  38             color_type color;
  39         };
  40
  41         //--------------------------------------------------------------------
  42         span_gouraud(alloc_type& alloc) :
  43             span_generator<color_type, alloc_type>(alloc),
  44             m_vertex(0)
  45         {
  46             m_cmd[0] = path_cmd_stop;
  47         }
  48
  49         //--------------------------------------------------------------------
  50         span_gouraud(alloc_type& alloc,
  51                      const color_type& c1,
  52                      const color_type& c2,
  53                      const color_type& c3,
  54                      double x1, double y1,
  55                      double x2, double y2,
  56                      double x3, double y3,
  57                      double d) :
  58             span_generator<color_type, alloc_type>(alloc)
  59         {
  60             colors(c1, c2, c3);
  61             triangle(x1, y1, x2, y2, x3, y3, d);
  62         }
  63
  64         //--------------------------------------------------------------------
  65         void colors(ColorT c1, ColorT c2, ColorT c3)
  66         {
  67             m_coord[0].color = c1;
  68             m_coord[1].color = c2;
  69             m_coord[2].color = c3;
  70         }
  71
  72         //--------------------------------------------------------------------
  73         // Sets the triangle and dilates it if needed.
  74         // The trick here is to calculate beveled joins in the vertices of the
  75         // triangle and render it as a 6-vertex polygon.
  76         // It's necessary to achieve numerical stability.
  77         // However, the coordinates to interpolate colors are calculated
  78         // as miter joins (calc_intersection).
  79         void triangle(double x1, double y1,
  80                       double x2, double y2,
  81                       double x3, double y3,
  82                       double d)
  83         {
  84             m_coord[0].x = m_x[0] = x1;
  85             m_coord[0].y = m_y[0] = y1;
  86             m_coord[1].x = m_x[1] = x2;
  87             m_coord[1].y = m_y[1] = y2;
  88             m_coord[2].x = m_x[2] = x3;
  89             m_coord[2].y = m_y[2] = y3;
  90             m_cmd[0] = path_cmd_move_to;
  91             m_cmd[1] = path_cmd_line_to;
  92             m_cmd[2] = path_cmd_line_to;
  93             m_cmd[3] = path_cmd_stop;
  94
  95             if(d != 0.0)
  96             {
  97                 dilate_triangle(m_coord[0].x, m_coord[0].y,
  98                                 m_coord[1].x, m_coord[1].y,
  99                                 m_coord[2].x, m_coord[2].y,
 100                                 m_x, m_y, d);
 101
 102                 calc_intersection(m_x[4], m_y[4], m_x[5], m_y[5],
 103                                   m_x[0], m_y[0], m_x[1], m_y[1],
 104                                   &m_coord[0].x, &m_coord[0].y);
 105
 106                 calc_intersection(m_x[0], m_y[0], m_x[1], m_y[1],
 107                                   m_x[2], m_y[2], m_x[3], m_y[3],
 108                                   &m_coord[1].x, &m_coord[1].y);
 109
 110                 calc_intersection(m_x[2], m_y[2], m_x[3], m_y[3],
 111                                   m_x[4], m_y[4], m_x[5], m_y[5],
 112                                   &m_coord[2].x, &m_coord[2].y);
 113                 m_cmd[3] = path_cmd_line_to;
 114                 m_cmd[4] = path_cmd_line_to;
 115                 m_cmd[5] = path_cmd_line_to;
 116                 m_cmd[6] = path_cmd_stop;
 117             }
 118         }
 119
 120         //--------------------------------------------------------------------
 121         // Vertex Source Interface to feed the coordinates to the rasterizer
 122         void rewind(unsigned)
 123         {
 124             m_vertex = 0;
 125         }
 126
 127         //--------------------------------------------------------------------
 128         unsigned vertex(double* x, double* y)
 129         {
 130             *x = m_x[m_vertex];
 131             *y = m_y[m_vertex];
 132             return m_cmd[m_vertex++];
 133         }
 134
 135
 136
 137     protected:
 138         //--------------------------------------------------------------------
 139         void arrange_vertices(coord_type* coord) const
 140         {
 141             coord[0] = m_coord[0];
 142             coord[1] = m_coord[1];
 143             coord[2] = m_coord[2];
 144
 145             if(m_coord[0].y > m_coord[2].y)
 146             {
 147                 coord[0] = m_coord[2];
 148                 coord[2] = m_coord[0];
 149             }
 150
 151             coord_type tmp;
 152             if(coord[0].y > coord[1].y)
 153             {
 154                 tmp      = coord[1];
 155                 coord[1] = coord[0];
 156                 coord[0] = tmp;
 157             }
 158
 159             if(coord[1].y > coord[2].y)
 160             {
 161                 tmp      = coord[2];
 162                 coord[2] = coord[1];
 163                 coord[1] = tmp;
 164             }
 165        }
 166
 167
 168     private:
 169         //--------------------------------------------------------------------
 170         coord_type m_coord[3];
 171         double m_x[8];
 172         double m_y[8];
 173         unsigned m_cmd[8];
 174         unsigned m_vertex;
 175     };
 176
 177 }
 178
 179 #endif
 180