flippen

flippen is a powerful Blender addon for automatically fixing face normals on architectural and general 3D models. It provides a suite of advanced, hybrid, and user-guided methods to make normals consistent, flip only wrongly oriented faces, and handle even the most stubborn or complex geometry.

---

Features

🟢 Smart Normal Correction

• Flip: Flips only faces that are wrongly oriented, using a neighbor-consistency check.
• Persistent Flip: Runs the neighbor-based method multiple times to catch stubborn or chain-reaction cases.
• Exterior Heuristic Flip: Uses ray casting to orient boundary faces based on exposure to empty space, robust for both exteriors and interior rooms.
• Flood Flip: Flood-fills from a point outside the mesh, propagating correct orientation to all connected faces.
• Hybrid Flip: Combines Persistent Flip with Blender's "Recalculate Outside" for maximum coverage.
• AO Flip: Uses ambient occlusion analysis to flip faces that are likely inward-facing based on occlusion.
• Manual Align: (Optional) Lets the user select a "correct" face and propagates orientation to all connected faces.

🟢 Batch Processing

• The main Flip operator supports batch processing of all selected mesh objects.

🟢 User-Friendly Sidebar UI

• All tools are available in the 3D View > Sidebar > flippen tab.
• No popups or dialogs—set your options and run with a single click.

🟢 Automatic Mode Handling

• Operators automatically switch to Edit Mode if needed.

🟢 User Guidance

• Clear instructions and tooltips are provided in the sidebar for each method.

🟢 Bug Reporting

• Direct link to the GitHub repository for feedback and bug reports in the Addon Preferences.

---

Installation

1. Download the flippen_02.py file from this repository.
2. In Blender, go to Edit > Preferences > Add-ons.
3. Click Install... and select the flippen_02.py file.
4. Enable the addon by checking the box next to "flippen."
5. The tools will appear in the flippen tab in the 3D View Sidebar (press N to open the sidebar if it's not visible).

---

Usage

1. Select Your Mesh Object(s)

• In Object Mode, select the mesh object(s) you want to fix.

2. Open the Sidebar

• Press N in the 3D Viewport to open the sidebar.
• Go to the flippen tab.

3. Choose Your Method

• Mode Dropdown: Choose the main operation mode for the Flip button:
  • Flip Normals: Neighbor-consistency check.
  • Make Normals Consistent: Blender's "Recalculate Outside."
  • Make Normals Consistent next Flip Normals: Recalculate then flip all.
• Max Passes: Set the number of passes for Persistent Flip and Hybrid Flip.

4. Run the Tools

• Flip: Runs the selected mode from the dropdown.
• Persistent Flip: Runs the neighbor-based method multiple times.
• Hybrid Flip: Runs Persistent Flip, then Recalculate Outside.
• AO Flip: Flips faces with low ambient occlusion (likely inward).
• Exterior Heuristic Flip: Uses ray casting to orient boundary faces based on exposure to empty space.
• Flood Flip: Flood-fills from outside the mesh to propagate correct orientation.
• Manual Align: (Optional) In Edit Mode, select a face you know is correct, then click "Run Manual Align" to propagate orientation.

5. Tips

• For best results, enable Blender's Face Orientation overlay to visually inspect normal directions (blue = outward, red = inward).
• Try different methods in sequence for complex or imported models.
• Use "Flood Flip" or "Exterior Heuristic Flip" for architectural exteriors and rooms.
• Use "Manual Align" for ultimate control in tricky cases.

---

Example Workflow

1. Select your mesh object.
2. Open the flippen tab in the sidebar.
3. Try Flip or Persistent Flip first.
4. If some faces are still wrong, try Hybrid Flip, Exterior Heuristic Flip, or Flood Flip.
5. For the last few stubborn faces, use Manual Align.

---

Advanced Methods Explained

• Neighbor Consistency Check: Flips faces whose normals disagree with the majority of their neighbors.
• Persistent Flip: Repeats the neighbor check multiple times to catch chain-reaction errors.
• Exterior Heuristic Flip: Uses ray casting to determine if a face is exposed to empty space (exterior) or is interior (e.g., inside a room), and orients accordingly.
• Flood Flip: Starts from a point outside the mesh and propagates correct orientation to all connected faces.
• Hybrid Flip: Combines Persistent Flip with Blender's "Recalculate Outside" for maximum coverage.
• AO Flip: Uses ambient occlusion (ray occlusion) to flip faces that are likely inward-facing.
• Manual Align: Lets the user select a "correct" face and propagates orientation to all connected faces.

---

Bug Reports & Feedback

Please report issues or suggest improvements at https://github.com/tankshield/flippen.

---

Credits & About

• Original author: Alexey Khlystov
• Fork and major enhancements: tankshield
• Development note:
  This addon was forked and edited completely in Cursor by a person with no prior knowledge of any coding!
  All improvements and new features were made possible thanks to AI-assisted development.

---

License

This addon is licensed under the GNU General Public License v2 or later (GPL-2.0-or-later).
See the LICENSE file for details.