Path intersections: fix bug when snapping creates intersections in th…

…e same column
tdewolff · Jan 12, 2025 · cd6e9ba · cd6e9ba
1 parent 498b63e
commit cd6e9ba
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Showing 2 changed files with 9 additions and 2 deletions.
diff --git a/path_intersection.go b/path_intersection.go
@@ -1936,6 +1936,7 @@ func bentleyOttmann(ps, qs Paths, op pathOp, fillRule FillRule) *Path {
 		// process all events of the current column
 		n := len(squares)
 		x := snap(queue.Top().X, BentleyOttmannEpsilon)
+	BentleyOttmannLoop:
 		for 0 < len(*queue) && snap(queue.Top().X, BentleyOttmannEpsilon) == x {
 			event := queue.Top()
 			// TODO: breaking intersections into two right and two left endpoints is not the most
@@ -2088,8 +2089,10 @@ func bentleyOttmann(ps, qs Paths, op pathOp, fillRule FillRule) *Path {
 				}
 
 				if 0 < len(*queue) && snap(queue.Top().X, BentleyOttmannEpsilon) == x {
-					// TODO: this happens very rarely, but apparently not a bug, why not?
-					fmt.Println("WARNING: new intersections in this column!")
+					//fmt.Println("WARNING: new intersections in this column!")
+					goto BentleyOttmannLoop // TODO: is this correct? seems to work
+					// TODO: almost parallel combined with overlapping segments may create many intersections considering order of
+					//       of overlapping segments and snapping after each column
 				} else if has {
 					// sort overlapping segments again
 					// this is needed when segments get cut and now become equal to the adjacent
@@ -2187,6 +2190,9 @@ func bentleyOttmann(ps, qs Paths, op pathOp, fillRule FillRule) *Path {
 					}
 				}
 				if next == nil {
+					fmt.Println(ps)
+					fmt.Println(op)
+					fmt.Println(qs)
 					panic("next node for result polygon is nil, probably buggy intersection code")
 					break
 				} else if next == first {

diff --git a/path_intersection_test.go b/path_intersection_test.go
@@ -1349,6 +1349,7 @@ func TestPathSettle(t *testing.T) {
 		{NonZero, "M3.013236014856396 2.0031317319105995L2.999840299505024 1.999840299505024zM2.999840299505024 2.000159700494976L3.0059914294253502 2.000159700494976L2.999840299505024 1.993265873649733zM3.000159700494976 1.999840299505024L2.360148227002341 1.999840299505024zM3.000159700494976 2.000159700494976L2.995741685965072 1.9901318032831057z", "M2.9998403000000002 1.99326587L3.00599143 2.0001597L2.9998403000000002 2.0001597z"},
 		{NonZero, "M0.070313747660117 7.153464460137324L0.062498752339883 7.148436252339883zM0.062498752339883 7.148438747660117L0.070313747660117 7.148438747660117z", ""},
 		{NonZero, "M1.828127495320234 7.578127495320234L1.828127495320234 7.562497504679766z M1.828122504679766 7.562502495320234L1.843752495320234 7.562502495320234z M1.841755539006334 7.57144770006846L1.841799370320234 7.562497504679766L1.826169379679766 7.562497504679766z M1.826169379679766 7.562502495320234L1.841799370320234 7.562502495320234z M1.841794379679766 7.562497504679766L1.841794379679766 7.567987843663488z M1.841794379679766 7.546872504679766L1.841794379679766 7.562502495320234L1.857424370320234 7.562502495320234z", "M1.82616938 7.5624975L1.84179438 7.5624975L1.84179438 7.5468725L1.85742437 7.5625025L1.84179935 7.5625025L1.84179438 7.5635166L1.84175554 7.5714477L1.8281275000000001 7.56362194L1.82617807 7.5625025z"},
+		{NonZero, "M0.5791607706898958 -0.0017990842812309893L0.5791256283147277 0.0006388019799032918z M0.24732247524502785 -0.0006388019799032918L0.5791440451040444 -0.0006388019799032918L0.5790883795787067 0.0032228100758402434z", "M0.24732248 -0.0006388L0.57914404 -0.0006388L0.57914404 -0.0006387200000000001L0.5791256300000001 0.0006388L0.57908838 0.00322281z"},
 	}
 	for _, tt := range tts {
 		t.Run(fmt.Sprint(tt.p), func(t *testing.T) {