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util/geometry: fix bad assumption in lineseg_closest_factor_impl

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cabs2(a - b) may return 0 even if a != b, if the difference is
sufficiently small.
This commit is contained in:
Andrei Alexeyev 2021-12-21 23:11:02 +02:00
parent 0c22d53bb0
commit 1853e5a56b
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GPG key ID: 72D26128040B9690
1 changed files with 4 additions and 17 deletions
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21
src/util/geometry.c
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@ -55,7 +55,10 @@ static double lineseg_closest_factor_impl(cmplx m, cmplx v) {
// v == vector from point of interest to A
double lm2 = cabs2(m);
assume(lm2 > 0);
if(UNLIKELY(lm2 == 0)) {
return 0;
}
double f = -creal(v * conj(m)) / lm2; // project v onto the line
f = clamp(f, 0, 1); // restrict it to segment
@ -65,18 +68,10 @@ static double lineseg_closest_factor_impl(cmplx m, cmplx v) {
// Return f such that a + f * (b - a) is the closest point on segment to p
double lineseg_closest_factor(LineSegment seg, cmplx p) {
if(UNLIKELY(seg.a == seg.b)) {
return 0;
}
return lineseg_closest_factor_impl(seg.b - seg.a, seg.a - p);
}
cmplx lineseg_closest_point(LineSegment seg, cmplx p) {
if(UNLIKELY(seg.a == seg.b)) {
return seg.a;
}
return clerp(seg.a, seg.b, lineseg_closest_factor_impl(seg.b - seg.a, seg.a - p));
}
@ -87,14 +82,6 @@ cmplx lineseg_closest_point(LineSegment seg, cmplx p) {
static double lineseg_circle_intersect_fallback(LineSegment seg, Circle c) {
double rad2 = c.radius * c.radius;
if(UNLIKELY(seg.a == seg.b)) {
if(cabs2(seg.a - c.origin) <= rad2) {
return 0;
}
return -1;
}
double f = lineseg_closest_factor_impl(seg.b - seg.a, seg.a - c.origin);
cmplx p = clerp(seg.a, seg.b, f);