Linefy is an fast, robust, cross-platform, drawing library for thick, colored, textured Lines, Polylines, Dots for Unity. The package includes the Polygonal Mesh, wich can import or create, manipulate polygon-based meshes. Using it, you can display the edged wireframe (which looks the same as in 3D software) and recalculate the high quality normals without gaps.
Linefy works in runtime, edit-mode, and allow to draw on Scene View (Editor.OnSceneGUI), so it good starting point to developing high performance, nice looking, custom editors. Pack contains custom Vector3 handle and Matrix4x4 handles.