typename range_value_type<CVsRange>::type
evaluate( std::size_t degree,
const CVsRange& cvs,
const KnotsRange& knots,
typename range_value_type<KnotsRange>::type u)
{
BOOST_CONCEPT_ASSERT(( boost::RandomAccessRangeConcept<CVsRange>));
BOOST_CONCEPT_ASSERT(( boost::RandomAccessRangeConcept<KnotsRange>));
std::size_t span = find_span( degree, boost::size( cvs), knots, u);
boost::array<typename range_value_type<KnotsRange>::type, NURBS_MAX_BASIS_DEGREE> N;
basis_functions( degree, u, span, knots, N.begin());
return evaluate( degree, cvs, N, span, u);
}
/**
* Plot a polygon
*
* \param nsfb framebuffer context
* \param p array of polygon vertices (x1, y1, x2, y2, ... , xN, yN)
* \param n number of polygon vertices (N)
* \param c fill colour
* \return true if no errors
*/
static bool polygon(nsfb_t *nsfb, const int *p, unsigned int n, nsfb_colour_t c)
{
int poly_x0, poly_y0; /* Bounding box top left corner */
int poly_x1, poly_y1; /* Bounding box bottom right corner */
int i, j; /* indexes */
int x0, x1; /* filled span extents */
int y; /* current y coordinate */
int y_max; /* bottom of plot area */
nsfb_bbox_t fline;
nsfb_plot_pen_t pen;
/* find no. of vertex values */
int v = n * 2;
/* Can't plot polygons with 2 or fewer vertices */
if (n <= 2)
return true;
pen.stroke_colour = c;
/* Find polygon bounding box */
poly_x0 = poly_x1 = *p;
poly_y0 = poly_y1 = p[1];
for (i = 2; i < v; i = i + 2) {
j = i + 1;
if (p[i] < poly_x0)
poly_x0 = p[i];
else if (p[i] > poly_x1)
poly_x1 = p[i];
if (p[j] < poly_y0)
poly_y0 = p[j];
else if (p[j] > poly_y1)
poly_y1 = p[j];
}
/* Don't try to plot it if it's outside the clip rectangle */
if (nsfb->clip.y1 < poly_y0 ||
nsfb->clip.y0 > poly_y1 ||
nsfb->clip.x1 < poly_x0 ||
nsfb->clip.x0 > poly_x1)
return true;
/* Find the top of the important area */
if (poly_y0 > nsfb->clip.y0)
y = poly_y0;
else
y = nsfb->clip.y0;
/* Find the bottom of the important area */
if (poly_y1 < nsfb->clip.y1)
y_max = poly_y1;
else
y_max = nsfb->clip.y1;
for (; y < y_max; y++) {
x1 = poly_x0 - 1;
/* For each row */
while (find_span(p, v, x1 + 1, y, &x0, &x1)) {
/* don't draw anything outside clip region */
if (x1 < nsfb->clip.x0)
continue;
else if (x0 < nsfb->clip.x0)
x0 = nsfb->clip.x0;
if (x0 > nsfb->clip.x1)
break;
else if (x1 > nsfb->clip.x1)
x1 = nsfb->clip.x1;
fline.x0 = x0;
fline.y0 = y;
fline.x1 = x1;
fline.y1 = y;
/* draw this filled span on current row */
nsfb->plotter_fns->line(nsfb, 1, &fline, &pen);
/* don't look for more spans if already at end of clip
* region or polygon */
if (x1 == nsfb->clip.x1 || x1 == poly_x1)
break;
}
}
return true;
}
