/*
Subdivide a bezier at T into LEFT_PART and RIGHT_PART
+ using deCasteljau's algorithm.
*/
void
-Bezier::subdivide (Real t, Bezier &left_part, Bezier &right_part)
+Bezier::subdivide (Real t, Bezier *left_part, Bezier *right_part) const
{
- Offset b2[3];
- Offset b1[2];
- Offset b0;
- for (int i = 0; i < 3; i++)
- b2[i] = control_[i] + t * (control_[i+1] - control_[i]);
- for (int i = 0; i < 2; i++)
- b1[i] = b2[i] + t * (b2[i+1] - b2[i]);
- b0 = b1[0] + t * (b1[1] - b1[0]);
- left_part.control_[0] = control_[0];
- left_part.control_[1] = b2[0];
- left_part.control_[2] = b1[0];
- left_part.control_[3] = b0;
- right_part.control_[0] = b0;
- right_part.control_[1] = b1[1];
- right_part.control_[2] = b2[2];
- right_part.control_[3] = control_[3];
+ Offset p[CONTROL_COUNT][CONTROL_COUNT];
+
+ for (int i = 0; i < CONTROL_COUNT ; i++)
+ p[i][CONTROL_COUNT - 1 ] = control_[i];
+ for (int j = CONTROL_COUNT - 2; j >= 0 ; j--)
+ for (int i = 0; i < CONTROL_COUNT -1; i++)
+ p[i][j] = p[i][j+1] + t * (p[i+1][j+1] - p[i][j+1]);
+ for (int i = 0; i < CONTROL_COUNT; i++)
+ {
+ left_part->control_[i]=p[0][CONTROL_COUNT - 1 - i];
+ right_part->control_[i]=p[i][i];
+ }
}
/*
*/
Bezier
-Bezier::extract (Real t_min, Real t_max)
+Bezier::extract (Real t_min, Real t_max) const
{
+ if ((t_min < 0) || (t_max) > 1)
+ programming_error
+ ("bezier extract arguments outside of limits: curve may have bad shape");
+ if (t_min >= t_max)
+ programming_error
+ ("lower bezier extract value not less than upper value: curve may have bad shape");
Bezier bez1, bez2, bez3, bez4;
if (t_min == 0.0)
- {
- for (int i = 0; i < CONTROL_COUNT; i++)
- bez2.control_[i] = control_[i];
- }
+ bez2 = *this;
else
- {
- subdivide (t_min, bez1, bez2);
- }
+ subdivide (t_min, &bez1, &bez2);
if (t_max == 1.0)
- {
return bez2;
- }
else
{
- bez2.subdivide ((t_max-t_min)/(1-t_min), bez3, bez4);
+ bez2.subdivide ((t_max-t_min)/(1-t_min), &bez3, &bez4);
return bez3;
}
}