diff options
| -rw-r--r-- | lineXline.c | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/lineXline.c b/lineXline.c new file mode 100644 index 0000000..0a07513 --- /dev/null +++ b/lineXline.c @@ -0,0 +1,64 @@ +#include <u.h> +#include <libc.h> +#include <geometry.h> + +int +lineXline(Point2 *r, Point2 p0, Point2 p1, Point2 p2, Point2 p3) +{ + Point2 dp[2], xp; + double m[2], c[2]; + + dp[0] = subpt2(p1, p0); m[0] = dp[0].y/dp[0].x; c[0] = p0.y - m[0]*p0.x; + fprint(2, "#1 := %gx + %g\n", m[0], c[0]); + dp[1] = subpt2(p3, p2); m[1] = dp[1].y/dp[1].x; c[1] = p2.y - m[1]*p2.x; + fprint(2, "#2 := %gx + %g\n", m[1], c[1]); + + if(m[0] == m[1]){ + if(c[0] == c[1]){ /* coincident */ + r[0] = p0; + r[1] = p1; + return 2; + } + /* parallel */ + return 0; + } + + /* intersecting */ + xp.x = (c[1]-c[0])/(m[0]-m[1]); + xp.y = m[0]*xp.x + c[0]; + xp.w = 1; + r[0] = xp; + return 1; +} + +void +usage(void) +{ + fprint(2, "usage: %s x0 y0 x1 y1 x2 y2 x3 y3\n", argv0); + exits("usage"); +} + +void +main(int argc, char *argv[]) +{ + Point2 p0, p1, p2, p3, r[2]; + int n; + + GEOMfmtinstall(); + ARGBEGIN{ + default: usage(); + }ARGEND + if(argc != 8) + usage(); + + p0.x = strtod(argv[0], nil); p0.y = strtod(argv[1], nil); + p1.x = strtod(argv[2], nil); p1.y = strtod(argv[3], nil); + p2.x = strtod(argv[4], nil); p2.y = strtod(argv[5], nil); + p3.x = strtod(argv[6], nil); p3.y = strtod(argv[7], nil); + + n = lineXline(r, p0, p1, p2, p3); + while(n--) + print("p%d: %v\n", n, r[n]); + + exits(nil); +} |