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#include <u.h>
#include <libc.h>
#include <draw.h>
#include <geometry.h>
#include <graphics.h>
/*
* comparison of a point p with an edge [e0 e1]
* p to the right: +
* p to the left: -
* p on the edge: 0
*/
static int
edgeptcmp(Point e0, Point e1, Point p)
{
Point3 e0p, e01, r;
p = subpt(p, e0);
e1 = subpt(e1, e0);
e0p = Vec3(p.x,p.y,0);
e01 = Vec3(e1.x,e1.y,0);
r = crossvec3(e0p, e01);
/* clamp to avoid overflow */
return fclamp(r.z, -1, 1); /* e0.x*e1.y - e0.y*e1.x */
}
Triangle
Trian(int x0, int y0, int x1, int y1, int x2, int y2)
{
return (Triangle){Pt(x0, y0), Pt(x1, y1), Pt(x2, y2)};
}
Triangle
Trianpt(Point p0, Point p1, Point p2)
{
return (Triangle){p0, p1, p2};
};
void
triangle(Image *dst, Triangle t, int thick, Image *src, Point sp)
{
Point pl[4];
pl[0] = t.p0;
pl[1] = t.p1;
pl[2] = t.p2;
pl[3] = pl[0];
poly(dst, pl, nelem(pl), 0, 0, thick, src, sp);
}
void
filltriangle(Image *dst, Triangle t, Image *src, Point sp)
{
Point pl[3];
pl[0] = t.p0;
pl[1] = t.p1;
pl[2] = t.p2;
fillpoly(dst, pl, nelem(pl), 0, src, sp);
}
int
ptintriangle(Point p, Triangle t)
{
/* counter-clockwise check */
return edgeptcmp(t.p0, t.p2, p) <= 0 &&
edgeptcmp(t.p2, t.p1, p) <= 0 &&
edgeptcmp(t.p1, t.p0, p) <= 0;
}
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