--- a/pkg/mesh/vertex.go	Thu Mar 21 08:19:21 2024 +0100
+++ b/pkg/mesh/vertex.go	Tue May 28 14:51:32 2024 +0200
@@ -93,10 +93,13 @@
 	// If the length of normal is near zero assume we have
 	// a plane constant in z with an average z value of
 	// the three vertices.
+	// A normal z component value of zero would cause a
+	// division by zero which would lead to an infinity value.
+	// In this case we apply the averaging, too.
 	// This should protect us from the effects of collinear
 	// geometries.
 	l := n.Length()
-	if l < 1e-7 {
+	if l < 1e-7 || math.Abs(n.Z) < 1e-7 {
 		sum := t[0].Z + t[1].Z + t[2].Z
 		return Plane3D{
 			A: 0,