fix: 腰面修复

Views/UserControl/ViewportData/Helper/ViewportHelperPro.cs

@@ -54,8 +54,16 @@ public class ViewportHelperPro
     {
         var meshBuilder = new MeshBuilder(true, false);
         foreach (var entity in entities)
-        {
-            meshBuilder.AddPolygon(new List<Vector3>() { entity.Point1, entity.Point2, entity.Point3 });
+        { 
+            if (entity.PlaneType == PlaneType.Girdle)
+            {
+                meshBuilder.AddTriangleFan(new List<Vector3>() { entity.Point1, entity.Point2, entity.Point3 },
+                    new List<Vector3>() { new Vector3(0,0,0), new Vector3(0,0,0), new Vector3(0,0,0) });
+            }
+            else
+            {
+                meshBuilder.AddPolygon(new List<Vector3>() { entity.Point1, entity.Point2, entity.Point3 });
+            }
         }
         var mesh = meshBuilder.ToMeshGeometry3D();