How to Convert 2D Polyylines, Polyface Meshes & Surfaces into 3D ACIS Solids
Transform closed 2D polylines, imported 3DS/OBJ polyface meshes, and watertight surface shells into true volumetric 3D ACIS solids (3DSOLID) for MASSPROP and Boolean operations.
⚡ Quick Executive Fix
Use EXTRUDE or PRESSPULL on closed 2D polylines, run CONVTOSOLID on watertight 3D meshes and thickened surfaces, or stitch enclosing planar/NURBS surfaces into a volumetric solid via SURFSCULPT.
1. Engineering Root-Cause Diagnosis inside the AC1032 DWG Database
Imported equipment models from SketchUp, Blender, Revit, or Rhino frequently arrive inside a `.dwg` as hollow **Polyface Meshes (`AcDbPolyFaceMesh`)**, **SubD Meshes (`AcDbSubDMesh`)**, or unjoined **3D Faces (`3DFACE`)**. Because hollow mesh shells lack an internal ACIS boundary-representation (`B-Rep`) volume, native CAD commands like `UNION`, `SUBTRACT`, `INTERFERE`, `MASSPROP` (center of gravity), and `FLATSHOT` reject them until they are healed into true **`3DSOLID`** entities.
2. Step-by-Step Resolution Protocol in AutoCAD & GstarCAD 2027
1. Convert Watertight Meshes via CONVTOSOLID
Select the mesh, set SMOOTHMESHCONVERT = 3 (Optimized, non-faceted coplanar faces merged), and run CONVTOSOLID. GstarCAD 2027 stitches adjacent triangular mesh faces into clean planar/analytical ACIS solid faces.
2. Stitch Enclosing Surfaces via SURFSCULPT
If your geometry consists of intersecting or touching `SURFACE` / `REGION` planes enclosing a watertight volume, select all bounding surfaces and run SURFSCULPT to solidify the interior void.
3. Thicken Open Surface Shells via THICKEN
If a civil terrain TIN or sheet-metal hood is an open single-sided surface rather than a closed volume, run CONVTOSURFACE followed by THICKEN (e.g., `Thickness = 5.0 mm`) to generate a true 3D solid shell.
3. Automated AutoLISP Diagnostic & Repair Script (C:MESH2SOLID)
Load the following production AutoLISP routine into GstarCAD 2027 or AutoCAD via APPLOAD (or add it to gcaddoc.lsp) to automate this repair across affected project files:
(defun C:MESH2SOLID ( / ss)
(setvar "SMOOTHMESHCONVERT" 3)
(setvar "DELOBJ" 1)
(princ "\nSelect closed Meshes or Polylines with thickness to convert to 3DSOLID: ")
(if (setq ss (ssget '((0 . "MESH,POLYLINE,LWPOLYLINE,CIRCLE"))))
(progn
(command "_.CONVTOSOLID" ss "")
(princ "\n[MESH2SOLID] Converted selected geometry with coplanar face merging (SMOOTHMESHCONVERT=3).")
)
)
(princ)
)4. Diagnostic System Variables & Edge-Case Matrix
| Failure Symptom / Scenario | Command / SysVar | Production Remediation Rule |
|---|---|---|
| Converted mesh has thousands of triangle seams | SMOOTHMESHCONVERT = 3 |
Merges coplanar triangular mesh facets into single clean ACIS planar faces. |
| CONVTOSOLID says 'Mesh is not watertight' | SURFSCULPT or THICKEN |
Open shell has boundary gaps; convert to surface and apply THICKEN. |
| Need volume & Center of Gravity (CoG) | MASSPROP |
Once converted to 3DSOLID, run MASSPROP to calculate volume and inertia. |
Experience Faster, Corruption-Free DWG Engineering in GstarCAD 2027
Built by Suzhou Gstarsoft Co., Ltd. (SSE: 688657), GstarCAD 2027 features multi-threaded DWG open/save, built-in RegApp/Scale-List scrubbers, and perpetual licensing.