Fix NaN halfedgeTangents (elalish#588)

fixed CreateTangents

src/manifold/src/smoothing.cpp

@@ -196,10 +196,13 @@ struct SmoothBezier {
     const glm::vec3 edgeNormal =
         (triNormal[edge.face] + triNormal[halfedge[edge.pairedHalfedge].face]) /
         2.0f;
-    glm::vec3 dir = glm::normalize(glm::cross(glm::cross(edgeNormal, edgeVec),
-                                              vertNormal[edge.startVert]));
+    glm::vec3 dir = SafeNormalize(glm::cross(glm::cross(edgeNormal, edgeVec),
+                                             vertNormal[edge.startVert]));
 
-    const float weight = glm::abs(glm::dot(dir, glm::normalize(edgeVec)));
+    float weight = glm::abs(glm::dot(dir, SafeNormalize(edgeVec)));
+    if (weight == 0) {
+      weight = 1;
+    }
     // Quadratic weighted bezier for circular interpolation
     const glm::vec4 bz2 =
         weight *

test/sdf_test.cpp

@@ -115,3 +115,21 @@ TEST(SDF, Resize) {
   EXPECT_EQ(layers.Status(), Manifold::Error::NoError);
   EXPECT_EQ(layers.Genus(), -8);
 }
+
+TEST(SDF, SineSurface) {
+  Mesh surface(LevelSet(
+      [](glm::vec3 p) {
+        float mid = glm::sin(p.x) + glm::sin(p.y);
+        return (p.z > mid - 0.5 && p.z < mid + 0.5) ? 1 : 0;
+      },
+      {glm::vec3(-4 * glm::pi<float>()), glm::vec3(4 * glm::pi<float>())}, 1));
+  Manifold smoothed = Manifold::Smooth(surface).Refine(2);
+
+  EXPECT_EQ(smoothed.Status(), Manifold::Error::NoError);
+  EXPECT_EQ(smoothed.Genus(), -2);
+
+#ifdef MANIFOLD_EXPORT
+  if (options.exportModels)
+    ExportMesh("sinesurface.glb", smoothed.GetMeshGL(), {});
+#endif
+}