ref: 20a1d2268d69a0bbe66d0f21999649133878377c
dir: /sys/src/libgeometry/point.c/
#include <u.h> #include <libc.h> #include <geometry.h> /* 2D */ Point2 Pt2(double x, double y, double w) { return (Point2){x, y, w}; } Point2 Vec2(double x, double y) { return (Point2){x, y, 0}; } Point2 addpt2(Point2 a, Point2 b) { return Pt2(a.x+b.x, a.y+b.y, a.w+b.w); } Point2 subpt2(Point2 a, Point2 b) { return Pt2(a.x-b.x, a.y-b.y, a.w-b.w); } Point2 mulpt2(Point2 p, double s) { return Pt2(p.x*s, p.y*s, p.w*s); } Point2 divpt2(Point2 p, double s) { return Pt2(p.x/s, p.y/s, p.w/s); } Point2 lerp2(Point2 a, Point2 b, double t) { t = fclamp(t, 0, 1); return Pt2( flerp(a.x, b.x, t), flerp(a.y, b.y, t), flerp(a.w, b.w, t) ); } double dotvec2(Point2 a, Point2 b) { return a.x*b.x + a.y*b.y; } double vec2len(Point2 v) { return sqrt(dotvec2(v, v)); } Point2 normvec2(Point2 v) { double len; len = vec2len(v); if(len == 0) return Pt2(0,0,0); return Pt2(v.x/len, v.y/len, 0); } /* * the edge function, from: * * Juan Pineda, “A Parallel Algorithm for Polygon Rasterization”, * Computer Graphics, Vol. 22, No. 8, August 1988 * * comparison of a point p with an edge [e0 e1] * p to the right: + * p to the left: - * p on the edge: 0 */ int edgeptcmp(Point2 e0, Point2 e1, Point2 p) { Point3 e0p, e01, r; p = subpt2(p, e0); e1 = subpt2(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 */ } /* * (PNPOLY) algorithm by W. Randolph Franklin */ int ptinpoly(Point2 p, Point2 *pts, ulong npts) { int i, j, c; for(i = c = 0, j = npts-1; i < npts; j = i++) if(p.y < pts[i].y != p.y < pts[j].y && p.x < (pts[j].x - pts[i].x) * (p.y - pts[i].y)/(pts[j].y - pts[i].y) + pts[i].x) c ^= 1; return c; } /* 3D */ Point3 Pt3(double x, double y, double z, double w) { return (Point3){x, y, z, w}; } Point3 Vec3(double x, double y, double z) { return (Point3){x, y, z, 0}; } Point3 addpt3(Point3 a, Point3 b) { return Pt3(a.x+b.x, a.y+b.y, a.z+b.z, a.w+b.w); } Point3 subpt3(Point3 a, Point3 b) { return Pt3(a.x-b.x, a.y-b.y, a.z-b.z, a.w-b.w); } Point3 mulpt3(Point3 p, double s) { return Pt3(p.x*s, p.y*s, p.z*s, p.w*s); } Point3 divpt3(Point3 p, double s) { return Pt3(p.x/s, p.y/s, p.z/s, p.w/s); } Point3 lerp3(Point3 a, Point3 b, double t) { t = fclamp(t, 0, 1); return Pt3( flerp(a.x, b.x, t), flerp(a.y, b.y, t), flerp(a.z, b.z, t), flerp(a.w, b.w, t) ); } double dotvec3(Point3 a, Point3 b) { return a.x*b.x + a.y*b.y + a.z*b.z; } Point3 crossvec3(Point3 a, Point3 b) { return Pt3( a.y*b.z - a.z*b.y, a.z*b.x - a.x*b.z, a.x*b.y - a.y*b.x, 0 ); } double vec3len(Point3 v) { return sqrt(dotvec3(v, v)); } Point3 normvec3(Point3 v) { double len; len = vec3len(v); if(len == 0) return Pt3(0,0,0,0); return Pt3(v.x/len, v.y/len, v.z/len, 0); }