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Merge pull request #52110 from nekomatata/fix-segment-intersection

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Fix segment intersection consistency in Geometry2D
This commit is contained in:
Camille Mohr-Daurat 2021-08-27 08:48:29 -07:00 committed by GitHub
parent 712bcf564f 511c80b2ec
commit 9206f561f5
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 41 additions and 12 deletions
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20
core/math/geometry_2d.h
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@ -182,7 +182,15 @@ public:
C = Vector2(C.x * Bn.x + C.y * Bn.y, C.y * Bn.x - C.x * Bn.y);
D = Vector2(D.x * Bn.x + D.y * Bn.y, D.y * Bn.x - D.x * Bn.y);
if ((C.y < 0 && D.y < 0) || (C.y >= 0 && D.y >= 0)) {
// Fail if C x B and D x B have the same sign (segments don't intersect).
// (equivalent to condition (C.y < 0 && D.y < CMP_EPSILON) || (C.y > 0 && D.y > CMP_EPSILON))
if (C.y * D.y > CMP_EPSILON) {
return false;
}
// Fail if segments are parallel or colinear.
// (when A x B == zero, i.e (C - D) x B == zero, i.e C x B == D x B)
if (Math::is_equal_approx(C.y, D.y)) {
return false;
}
@ -193,7 +201,7 @@ public:
return false;
}
// (4) Apply the discovered position to line A-B in the original coordinate system.
// Apply the discovered position to line A-B in the original coordinate system.
if (r_result) {
*r_result = p_from_a + B * ABpos;
}
@ -353,8 +361,14 @@ public:
for (int i = 0; i < c; i++) {
const Vector2 &v1 = p[i];
const Vector2 &v2 = p[(i + 1) % c];
if (segment_intersects_segment(v1, v2, p_point, further_away, nullptr)) {
Vector2 res;
if (segment_intersects_segment(v1, v2, p_point, further_away, &res)) {
intersections++;
if (res.is_equal_approx(p_point)) {
// Point is in one of the polygon edges.
return true;
}
}
}

33
tests/test_geometry_2d.h
View file

@ -51,8 +51,6 @@ TEST_CASE("[Geometry2D] Point in circle") {
CHECK_FALSE(Geometry2D::is_point_in_circle(Vector2(7, -42), Vector2(4, -40), 3.5));
// This tests points on the edge of the circle. They are treated as being inside the circle.
// In `is_point_in_triangle` and `is_point_in_polygon` they are treated as being outside, so in order the make
// the behaviour consistent this may change in the future (see issue #44717 and PR #44274).
CHECK(Geometry2D::is_point_in_circle(Vector2(1.0, 0.0), Vector2(0, 0), 1.0));
CHECK(Geometry2D::is_point_in_circle(Vector2(0.0, -1.0), Vector2(0, 0), 1.0));
}
@ -66,7 +64,7 @@ TEST_CASE("[Geometry2D] Point in triangle") {
CHECK_FALSE(Geometry2D::is_point_in_triangle(Vector2(0, 0), Vector2(1, 4), Vector2(3, 2), Vector2(5, 4)));
// This tests points on the edge of the triangle. They are treated as being outside the triangle.
// In `is_point_in_circle` they are treated as being inside, so in order the make
// In `is_point_in_circle` and `is_point_in_polygon` they are treated as being inside, so in order the make
// the behaviour consistent this may change in the future (see issue #44717 and PR #44274).
CHECK_FALSE(Geometry2D::is_point_in_triangle(Vector2(1, 1), Vector2(-1, 1), Vector2(0, -1), Vector2(1, 1)));
CHECK_FALSE(Geometry2D::is_point_in_triangle(Vector2(0, 1), Vector2(-1, 1), Vector2(0, -1), Vector2(1, 1)));
@ -95,11 +93,16 @@ TEST_CASE("[Geometry2D] Point in polygon") {
CHECK(Geometry2D::is_point_in_polygon(Vector2(370, 55), p));
CHECK(Geometry2D::is_point_in_polygon(Vector2(-160, 190), p));
// This tests points on the edge of the polygon. They are treated as being outside the polygon.
// In `is_point_in_circle` they are treated as being inside, so in order the make
// the behaviour consistent this may change in the future (see issue #44717 and PR #44274).
CHECK_FALSE(Geometry2D::is_point_in_polygon(Vector2(68, 112), p));
CHECK_FALSE(Geometry2D::is_point_in_polygon(Vector2(-88, 120), p));
// This tests points on the edge of the polygon. They are treated as being inside the polygon.
int c = p.size();
for (int i = 0; i < c; i++) {
const Vector2 &p1 = p[i];
CHECK(Geometry2D::is_point_in_polygon(p1, p));
const Vector2 &p2 = p[(i + 1) % c];
Vector2 midpoint((p1 + p2) * 0.5);
CHECK(Geometry2D::is_point_in_polygon(midpoint, p));
}
}
TEST_CASE("[Geometry2D] Polygon clockwise") {
@ -140,9 +143,21 @@ TEST_CASE("[Geometry2D] Segment intersection.") {
CHECK(r.is_equal_approx(Vector2(0, 0)));
CHECK_FALSE(Geometry2D::segment_intersects_segment(Vector2(-1, 1), Vector2(1, -1), Vector2(1, 1), Vector2(0.1, 0.1), &r));
CHECK_FALSE(Geometry2D::segment_intersects_segment(Vector2(-1, 1), Vector2(1, -1), Vector2(0.1, 0.1), Vector2(1, 1), &r));
CHECK_FALSE_MESSAGE(
Geometry2D::segment_intersects_segment(Vector2(-1, 1), Vector2(1, -1), Vector2(0, 1), Vector2(1, -1), &r),
Geometry2D::segment_intersects_segment(Vector2(-1, 1), Vector2(1, -1), Vector2(0, 1), Vector2(2, -1), &r),
"Parallel segments should not intersect.");
CHECK_MESSAGE(
Geometry2D::segment_intersects_segment(Vector2(0, 0), Vector2(0, 1), Vector2(0, 0), Vector2(1, 0), &r),
"Touching segments should intersect.");
CHECK(r.is_equal_approx(Vector2(0, 0)));
CHECK_MESSAGE(
Geometry2D::segment_intersects_segment(Vector2(0, 1), Vector2(0, 0), Vector2(0, 0), Vector2(1, 0), &r),
"Touching segments should intersect.");
CHECK(r.is_equal_approx(Vector2(0, 0)));
}
TEST_CASE("[Geometry2D] Closest point to segment") {