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agg_span_gouraud.h
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agg_span_gouraud.h
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//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software
// is granted provided this copyright notice appears in all copies.
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
// mcseemagg@yahoo.com
// http://www.antigrain.com
//----------------------------------------------------------------------------
#ifndef AGG_SPAN_GOURAUD_INCLUDED
#define AGG_SPAN_GOURAUD_INCLUDED
#include "agg_basics.h"
#include "agg_math.h"
namespace agg
{
//============================================================span_gouraud
template<class ColorT> class span_gouraud
{
public:
typedef ColorT color_type;
struct coord_type
{
double x;
double y;
color_type color;
};
//--------------------------------------------------------------------
span_gouraud() :
m_vertex(0)
{
m_cmd[0] = path_cmd_stop;
}
//--------------------------------------------------------------------
span_gouraud(const color_type& c1,
const color_type& c2,
const color_type& c3,
double x1, double y1,
double x2, double y2,
double x3, double y3,
double d) :
m_vertex(0)
{
colors(c1, c2, c3);
triangle(x1, y1, x2, y2, x3, y3, d);
}
//--------------------------------------------------------------------
void colors(ColorT c1, ColorT c2, ColorT c3)
{
m_coord[0].color = c1;
m_coord[1].color = c2;
m_coord[2].color = c3;
}
//--------------------------------------------------------------------
// Sets the triangle and dilates it if needed.
// The trick here is to calculate beveled joins in the vertices of the
// triangle and render it as a 6-vertex polygon.
// It's necessary to achieve numerical stability.
// However, the coordinates to interpolate colors are calculated
// as miter joins (calc_intersection).
void triangle(double x1, double y1,
double x2, double y2,
double x3, double y3,
double d)
{
m_coord[0].x = m_x[0] = x1;
m_coord[0].y = m_y[0] = y1;
m_coord[1].x = m_x[1] = x2;
m_coord[1].y = m_y[1] = y2;
m_coord[2].x = m_x[2] = x3;
m_coord[2].y = m_y[2] = y3;
m_cmd[0] = path_cmd_move_to;
m_cmd[1] = path_cmd_line_to;
m_cmd[2] = path_cmd_line_to;
m_cmd[3] = path_cmd_stop;
if(d != 0.0)
{
dilate_triangle(m_coord[0].x, m_coord[0].y,
m_coord[1].x, m_coord[1].y,
m_coord[2].x, m_coord[2].y,
m_x, m_y, d);
calc_intersection(m_x[4], m_y[4], m_x[5], m_y[5],
m_x[0], m_y[0], m_x[1], m_y[1],
&m_coord[0].x, &m_coord[0].y);
calc_intersection(m_x[0], m_y[0], m_x[1], m_y[1],
m_x[2], m_y[2], m_x[3], m_y[3],
&m_coord[1].x, &m_coord[1].y);
calc_intersection(m_x[2], m_y[2], m_x[3], m_y[3],
m_x[4], m_y[4], m_x[5], m_y[5],
&m_coord[2].x, &m_coord[2].y);
m_cmd[3] = path_cmd_line_to;
m_cmd[4] = path_cmd_line_to;
m_cmd[5] = path_cmd_line_to;
m_cmd[6] = path_cmd_stop;
}
}
//--------------------------------------------------------------------
// Vertex Source Interface to feed the coordinates to the rasterizer
void rewind(unsigned)
{
m_vertex = 0;
}
//--------------------------------------------------------------------
unsigned vertex(double* x, double* y)
{
*x = m_x[m_vertex];
*y = m_y[m_vertex];
return m_cmd[m_vertex++];
}
protected:
//--------------------------------------------------------------------
void arrange_vertices(coord_type* coord) const
{
coord[0] = m_coord[0];
coord[1] = m_coord[1];
coord[2] = m_coord[2];
if(m_coord[0].y > m_coord[2].y)
{
coord[0] = m_coord[2];
coord[2] = m_coord[0];
}
coord_type tmp;
if(coord[0].y > coord[1].y)
{
tmp = coord[1];
coord[1] = coord[0];
coord[0] = tmp;
}
if(coord[1].y > coord[2].y)
{
tmp = coord[2];
coord[2] = coord[1];
coord[1] = tmp;
}
}
private:
//--------------------------------------------------------------------
coord_type m_coord[3];
double m_x[8];
double m_y[8];
unsigned m_cmd[8];
unsigned m_vertex;
};
}
#endif