insideOUT — Documentation

1. Installation

Blender 4.2 and later — Extensions

1. Download the zip for your platform from Superhive:
   • Windows x64 → insideOUT-2.0.0.zip (CPU + optional NVIDIA CUDA engine)
   • Linux x64 → insideOUT-2.0.0-linux.zip (CPU + optional NVIDIA CUDA engine)
   • macOS Apple Silicon → insideOUT-2.0.0-macos-arm64.zip (CPU)
2. Open Blender. Go to Edit → Preferences → Get Extensions → Install from Disk (top-right dropdown).
3. Select the zip. Blender installs and enables the extension automatically.
4. Panel appears in View3D → Sidebar (N) → insideOUT.

Upgrading from 1.x: remove the old insideOUT first (Preferences → Get Extensions → insideOUT → Remove), then install 2.0.0. The internal protocol between add-on and native core changed; mixing files from both versions will not work.

Platform notes

• Self-contained: no dependencies, no Python packages, no admin rights required. Blender 4.2 or newer.
• Native CPU core is a tiny C++ binary bundled in the zip — DeleteInsideFacesCore.exe on Windows, DeleteInsideFacesCore on Linux/macOS (the add-on sets +x on first load if needed).
• Windows x64 and Linux x64 also include DeleteInsideFacesCoreCuda, an optional NVIDIA CUDA accelerator (Turing / GTX 16xx / RTX 20xx and newer; only the NVIDIA driver is needed). If present, insideOUT selects CUDA automatically and shows an Engine selector under Advanced. If missing, the CPU core is used silently.
• Three platforms: Windows x64, Linux x64, macOS Apple Silicon. macOS is CPU-only.

2. Quick start

1. Select the mesh objects you want cleaned.
2. Open the N panel → insideOUT.
3. Leave the defaults (Gap Tolerance 0.1 mm, transparent materials ignored, Mode Optimize Selected Together).
4. Click Clean Up: Objects, then Faces.

That is the whole tool. One click removes every object that is completely hidden, then every face that cannot be seen from outside. Prefer to look first? The small select buttons next to each Delete button show you what would go, without deleting anything.

3. The panel

The panel lives in the View3D sidebar under the insideOUT tab.

Top section — the three settings that matter:

• Gap Tolerance — closes hairline seams between parts (see Settings).
• Ignore Transparent Materials — glass does not hide what is behind it.
• Mode — how the selection is treated.

Action buttons:

• Delete Hidden Objects — removes selected objects that are completely enclosed. The small select icon next to it only selects them.
• Delete Interior Faces — removes faces that cannot be seen from outside. The select icon next to it enters Edit Mode with those faces selected instead.
• Clean Up: Objects, then Faces — runs both in sequence.

The Advanced fold holds Engine (only when the CUDA core is present), Rays, Min Island and Filter Strays. After a run, the panel reports faces removed or selected, objects changed and deleted, rays used, engine and elapsed time.

4. Workflows

Delete Hidden Objects

Removes entire objects when not a single face of them can be seen from outside. Faces of partially visible objects are not touched. Use it for CAD assemblies with thousands of internal fasteners, brackets and pipes, kitbash scenes with parts buried inside hulls, or any scene with many fully enclosed objects.

One confirmed visible face keeps the object. A flush hatch that only shows its top surface stays.

Delete Interior Faces

Removes individual hidden faces from the selected meshes. Topology is preserved — quads stay quads, n-gons stay n-gons, UVs and materials on surviving faces are untouched. Objects that end up with no faces are removed when that is safe (no children, animation or constraints).

Clean Up: Objects, then Faces

Runs Delete Hidden Objects, then Delete Interior Faces on whatever is left selected. The recommended one-click path for assemblies.

Select instead of delete

The small select buttons run exactly the same computation but only select. For objects: the hidden objects become the selection. For faces: Blender enters Edit Mode in face-select mode with the interior faces selected. Inspect, adjust settings, or press X → Faces yourself.

5. Settings reference

Gap Tolerance

Default 0.1 mm (scene units). Faces that are visible only through a crack narrower than this are treated as hidden. CAD assemblies are full of parts that touch with a hairline gap; without this, rays slip through those seams and keep interior faces alive as scattered fragments. Real openings stay open: a 5 mm slot is still visible at 0.3 mm tolerance. Set 0 to disable. Cost is about 1 % run time.

Ignore Transparent Materials

Default on. Faces whose material is transparent neither hide what is behind them nor get deleted. Detected from Glass, Transparent, Refraction and Translucent BSDF nodes, from a Principled BSDF with Transmission above 0 or Alpha below 1, and from material names containing glass, window, transparent, acrylic, clear or lens. Also respected by Delete Hidden Objects: an object is judged by its opaque faces.

Mode

• Optimize Each Object Alone — each selected object is processed on its own. Each object only sees itself; nothing else blocks its rays. Use it to clean many separate assets in one go.
• Optimize Selected Together (default) — all selected objects form one scene. Every object blocks rays for every other, and all of them get cleaned. This is what you want for assemblies.
• Optimize Active Only — all selected objects form one scene, but only the active object is cleaned. The others just block rays. Good for one hero asset inside its surroundings.

Advanced — Engine

Shown only when the CUDA core is present. CUDA is selected automatically; switch to CPU to compare or if the GPU is busy. Both give identical results.

Advanced — Rays

Number of ray origins swept around the scene. Default 2048; range 512 – 8192. Every origin is always used — there is no early exit, so more rays only ever find more. Raise it for models with very narrow, deep openings.

Advanced — Min Island

Default 0 (off). Removes small islands of kept faces — fragments smaller than this many faces that are only part of a larger mesh piece and that are not directly visible along their own normal. Whole separate objects are never removed. A cosmetic option; it can delete a visible sliver, so it is off by default.

Advanced — Filter Strays / Aggressiveness

Default off. Re-tests kept faces with fewer than 1 (or 2) kept neighbours and removes them if they are not directly visible. Like Min Island, cosmetic and off by default. With Gap Tolerance active you will rarely need it.

6. Recipes by use case

CAD imports (STEP / IGES / IFC)

1. Apply modifiers if any.
2. Select the assembly.
3. Mode: Optimize Selected Together. Gap Tolerance 0.1 – 0.5 mm.
4. Click Clean Up: Objects, then Faces.

Expect 30 – 95 % reduction depending on how enclosed the assembly is.

Many separate assets at once

1. Select all of them.
2. Mode: Optimize Each Object Alone.
3. Click Delete Interior Faces.

One hero asset inside a scene

1. Select the surroundings and the asset, make the asset active.
2. Mode: Optimize Active Only.
3. Use the select icon first to preview, then Delete Interior Faces.

Products with glass

1. Keep the glass objects selected.
2. Leave Ignore Transparent Materials on.
3. Run as usual — what you see through the window stays.

7. What is new in 2.0

• Watertight ray casting. The old ray/triangle test let rays slip through shared edges of closed shells, especially on grid-aligned CAD coordinates. That was the source of the scattered leftover triangles and fragmented interiors some users saw. Fixed at the root, on CPU and CUDA.
• Coincident faces. A lid lying on a frame, a decal on a hull, duplicated geometry — both copies used to end up as a checkerboard of kept and deleted triangles. Now both are kept.
• Gap Tolerance. New. Closes hairline seams between touching parts.
• Transparent materials. New. Glass no longer hides what is behind it.
• Concave n-gons are triangulated correctly (they used to create phantom triangles that blocked rays).
• No early exit. Every ray origin is always swept. Faces visible only from rare directions are no longer at risk.
• Hidden-object pass keeps an object as soon as one face is visible, no longer culls rays by normal direction (flipped normals are fine), and handles flush hatches.
• Simpler panel. Coarse / Fine / Precise, cone settings, backface cull and ray presets are gone. One algorithm at its most thorough settings, three settings in front of you, one Clean Up button.

8. Troubleshooting

Visible faces got deleted

• Lower Gap Tolerance (or set 0) if the model has real slots narrower than the tolerance.
• Switch off Filter Strays and set Min Island to 0 if you enabled them.
• Check that the faces are not sunk below a neighbouring surface: a panel lying 0.5 mm under a hull skin is hidden by definition.
• Use the select icon to preview before deleting.

Hidden faces remain

• Raise Gap Tolerance to 0.3 – 1 mm: leftover fragments are almost always faces seen through a seam.
• Try Min Island 20 – 50 for cosmetic cleanup of remaining specks.
• Raise Rays only if the model has deep narrow openings; it does not help with seam fragments.

Ragged borders where faces were removed

insideOUT never cuts or rebuilds geometry; the border of a removed region follows the existing triangles. On CAD tessellations with long sliver triangles the border looks ragged. Use Blender's Limited Dissolve or a Decimate (Planar) modifier afterwards if you need clean edges.

Cancel does nothing

Cancel kills the worker process immediately. If the UI stays frozen for more than a second, check the system console.

"Exe not found" error

The native binary failed to install with the add-on. Reinstall the zip. On Linux make sure the extensions folder is not on a noexec mount.

CUDA engine is not visible

The Engine selector appears only when the CUDA core is present (Windows x64 and Linux x64 packages) and only under Advanced. Without it the CPU core is used automatically. Results are identical.

macOS blocks the helper on first run

The macOS build includes an unsigned native binary. If macOS blocks it, remove quarantine from the installed add-on folder and restart Blender:

xattr -dr com.apple.quarantine "/path/to/insideout"chmod +x "/path/to/insideout/DeleteInsideFacesCore"

9. Limits & known caveats

• Modifiers are ignored. The add-on reads the base mesh. Apply Subdivision / Mirror / Boolean before running.
• Deletion only, no remeshing. Borders follow the input triangulation.
• Sampling. Visibility is tested with thousands of ray origins around the scene. A face at the bottom of an extremely deep, narrow well can be missed by every origin; raise Rays for such models.
• Transparency detection is heuristic. Rename the material to contain “glass” or use a Glass / Transparent BSDF if a material is not recognised.
• Runs cannot be partially undone — Blender's undo treats each run as one step. Ctrl+Z restores everything.

10. FAQ

Will it damage my UVs, materials, or normals?

No. insideOUT only deletes whole faces. UVs, normals, custom split normals and material assignments on surviving faces are untouched.

Does it work on open meshes (shells, planes, single-sided geometry)?

Yes. Rays hit faces from either side, so single-sided geometry is treated as visible from both sides. Closed geometry simply hides more.

Does it respect glass / transparent materials?

Yes, since 2.0. Ignore Transparent Materials is on by default.

Is the result deterministic?

Yes. Same input and settings give the same result, on CPU and CUDA.

Can I cancel a long run?

Yes. Cancel kills the background worker immediately.

Does it work in headless / background mode?

The add-on uses a modal operator with a UI timer; running it from a background script is not officially supported.

Where does the native binary come from?

A standalone C++ program written by the author, cross-compiled and shipped inside the zip. No external dependencies, no internet access, no telemetry.

Which platforms are supported?

Windows x64, Linux x64 (both with optional CUDA), macOS Apple Silicon (CPU).

Will updates be free?

Yes, every 2.x update is included.

11. Support

Questions, edge-case meshes, or feature requests?

• Use Superhive messages on the product page — the author replies personally.
• Include a screenshot of the panel settings, a screenshot of the mesh, and if possible a small .blend repro.

Bug reports with a repro file get priority.