1//----------------------------------------------------------------------------
2// Anti-Grain Geometry - Version 2.4
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
22namespace agg
23{
24
25    //============================================================span_gouraud
26    template<class ColorT> class span_gouraud
27    {
28    public:
29        typedef ColorT color_type;
30
31        struct coord_type
32        {
33            double x;
34            double y;
35            color_type color;
36        };
37
38        //--------------------------------------------------------------------
39        span_gouraud() :
40            m_vertex(0)
41        {
42            m_cmd[0] = path_cmd_stop;
43        }
44
45        //--------------------------------------------------------------------
46        span_gouraud(const color_type& c1,
47                     const color_type& c2,
48                     const color_type& c3,
49                     double x1, double y1,
50                     double x2, double y2,
51                     double x3, double y3,
52                     double d) :
53            m_vertex(0)
54        {
55            colors(c1, c2, c3);
56            triangle(x1, y1, x2, y2, x3, y3, d);
57        }
58
59        //--------------------------------------------------------------------
60        void colors(ColorT c1, ColorT c2, ColorT c3)
61        {
62            m_coord[0].color = c1;
63            m_coord[1].color = c2;
64            m_coord[2].color = c3;
65        }
66
67        //--------------------------------------------------------------------
68        // Sets the triangle and dilates it if needed.
69        // The trick here is to calculate beveled joins in the vertices of the
70        // triangle and render it as a 6-vertex polygon.
71        // It's necessary to achieve numerical stability.
72        // However, the coordinates to interpolate colors are calculated
73        // as miter joins (calc_intersection).
74        void triangle(double x1, double y1,
75                      double x2, double y2,
76                      double x3, double y3,
77                      double d)
78        {
79            m_coord[0].x = m_x[0] = x1;
80            m_coord[0].y = m_y[0] = y1;
81            m_coord[1].x = m_x[1] = x2;
82            m_coord[1].y = m_y[1] = y2;
83            m_coord[2].x = m_x[2] = x3;
84            m_coord[2].y = m_y[2] = y3;
85            m_cmd[0] = path_cmd_move_to;
86            m_cmd[1] = path_cmd_line_to;
87            m_cmd[2] = path_cmd_line_to;
88            m_cmd[3] = path_cmd_stop;
89
90            if(d != 0.0)
91            {
92                dilate_triangle(m_coord[0].x, m_coord[0].y,
93                                m_coord[1].x, m_coord[1].y,
94                                m_coord[2].x, m_coord[2].y,
95                                m_x, m_y, d);
96
97                calc_intersection(m_x[4], m_y[4], m_x[5], m_y[5],
98                                  m_x[0], m_y[0], m_x[1], m_y[1],
99                                  &m_coord[0].x, &m_coord[0].y);
100
101                calc_intersection(m_x[0], m_y[0], m_x[1], m_y[1],
102                                  m_x[2], m_y[2], m_x[3], m_y[3],
103                                  &m_coord[1].x, &m_coord[1].y);
104
105                calc_intersection(m_x[2], m_y[2], m_x[3], m_y[3],
106                                  m_x[4], m_y[4], m_x[5], m_y[5],
107                                  &m_coord[2].x, &m_coord[2].y);
108                m_cmd[3] = path_cmd_line_to;
109                m_cmd[4] = path_cmd_line_to;
110                m_cmd[5] = path_cmd_line_to;
111                m_cmd[6] = path_cmd_stop;
112            }
113        }
114
115        //--------------------------------------------------------------------
116        // Vertex Source Interface to feed the coordinates to the rasterizer
117        void rewind(unsigned)
118        {
119            m_vertex = 0;
120        }
121
122        //--------------------------------------------------------------------
123        unsigned vertex(double* x, double* y)
124        {
125            *x = m_x[m_vertex];
126            *y = m_y[m_vertex];
127            return m_cmd[m_vertex++];
128        }
129
130    protected:
131        //--------------------------------------------------------------------
132        void arrange_vertices(coord_type* coord) const
133        {
134            coord[0] = m_coord[0];
135            coord[1] = m_coord[1];
136            coord[2] = m_coord[2];
137
138            if(m_coord[0].y > m_coord[2].y)
139            {
140                coord[0] = m_coord[2];
141                coord[2] = m_coord[0];
142            }
143
144            coord_type tmp;
145            if(coord[0].y > coord[1].y)
146            {
147                tmp      = coord[1];
148                coord[1] = coord[0];
149                coord[0] = tmp;
150            }
151
152            if(coord[1].y > coord[2].y)
153            {
154                tmp      = coord[2];
155                coord[2] = coord[1];
156                coord[1] = tmp;
157            }
158       }
159
160    private:
161        //--------------------------------------------------------------------
162        coord_type m_coord[3];
163        double m_x[8];
164        double m_y[8];
165        unsigned m_cmd[8];
166        unsigned m_vertex;
167    };
168
169}
170
171#endif
172
173