Tommaso BianchiandClaude Opus 5
8b568b7b9d
Tommaso asked the question that names the real defect: if the sketch was open, why was the same sketch shaded closed and offered for extrude? Because the two halves used different tolerances. region_loops shades a region closed at 1e-3 mm; connected_loop chained at 1e-3; the kernel welded at 1e-4 and OCCT matched vertices at 1e-7. The 2.28e-5 mm gap in the reported sketch did not cause that disagreement, it only made it visible — and fixing the gap alone would have left the contradiction in place, ready to reappear anywhere in (1e-4, 1e-3]. kSketchJoinTol now lives in SketchEngine.hpp and is the only place the number exists. region_loops, loop_report, connected_loop and entities_to_wires all read it through sketch_join_tol(). The viewport cannot promise a region the kernel refuses to build. The welding is optional, because a kernel that silently closes loops should let you say no: "Auto-close sketch loops" in Preferences, default ON, no restart. OFF means only exactly coincident endpoints join — and since both halves read the same value, the viewport simply stops shading the region closed, so an open loop is visible rather than welded behind your back. No separate UI needed for that; it falls out of sharing one number. Details that matter. The kernel defaults to auto-close ON independently of the GUI, so headless and MCP callers behave like the viewport instead of inheriting an unset preference. With the tolerance at 0 the comparisons become <=, because OFF must mean exact, not broken. OCCT never receives a zero vertex tolerance — it is clamped to Precision::Confusion. The preference is pushed from EVERY entry that starts a sketch session, not just begin(): a Constrain session enters through begin_constrain / begin_constrain_entities and uses region_loops and connected_loop, so a single push site would have left those sessions running on whatever the previous one set. begin_imported_transform is excluded deliberately — it works on imported regions, not chained entities. Tests: a loop with one joint open by 9e-4 mm, given out of traversal order, builds a closed four-edge wire; with auto-close off the same loop yields no wire; and an exactly closed loop still builds with auto-close off, proving OFF means exact. Kernel 66104 assertions / 606 cases green. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_011FbJKJAJxxkhDTs9XdZzKA
OrcaSlicer: an open source Next-Gen Slicing Software for Precision 3D Prints.
Optimize your prints with ultra-fast slicing, intelligent support generation, and seamless printer compatibility—engineered for perfection.
Official links and community
Official Website:
Github Repository:
Follow us:
Join our Discord community:
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Main features
- Advanced Calibration Tools
Comprehensive suite: temperature towers, flow rate, retraction & more for optimal performance. - Precise Wall and Seam Control
Adjust outer wall spacing and apply scarf seams to enhance print accuracy. - Sandwich Mode and Polyholes Support
Use varied infill patterns and accurate hole shapes for improved clarity. - Overhang and Support Optimization
Modify geometry for printable overhangs with precise support placement. - Granular Controls and Customization
Fine-tune print speed, layer height, pressure, and temperature with precision. - Network Printer Support
Seamless integration with Klipper, PrusaLink, and OctoPrint for remote control. - Mouse Ear Brims & Adaptive Bed Mesh
Automatic brims and adaptive mesh calibration ensure consistent adhesion. - User-Friendly Interface
Intuitive drag-and-drop design with pre-made profiles for popular printers. - Open-Source & Community Driven
Regular updates fueled by continuous community contributions. - Wide Printer Compatibility
Supports a broad range of printers: Bambu Lab, Prusa, Creality, Voron, and more. - Additional features can be found in the change notes.
Wiki
The wiki aims to provide a detailed explanation of the slicer settings, including how to maximize their use and how to calibrate and set up your printer.
Download
Stable Release
📥 Download the Latest Stable Release
Visit our GitHub Releases page for the latest stable version of OrcaSlicer, recommended for most users.
Nightly Builds
🌙 Download the Latest Nightly Build
Explore the latest developments in OrcaSlicer with our nightly builds. Feedback on these versions is highly appreciated.
Belt Printer Builds
The nightly release ships two parallel builds: the standard build and a belt-printer build. Both are attached to the same release — tell them apart by the filename suffix:
- Standard — no suffix (e.g.
OrcaSlicer_Windows_Installer_x64_nightly.exe) - Belt —
_beltsuffix (e.g.OrcaSlicer_Windows_Installer_x64_nightly_belt.exe)
The _belt builds add experimental support for belt / conveyor (infinite-Z) printers, where the model is sliced against a tilted belt surface instead of a flat horizontal bed. They include ready-to-use belt printer profiles, the full belt slicing pipeline (mesh rotation and G-code transforms), belt-aware support generation, and a tilted-bed preview.
⚠️ Belt printer support is under active development and is not yet merged into
main— it currently ships only in these parallel_beltbuilds, produced from thebelt-printerbranch. See tracking PR #14394 and the original documentation in #12998.
How to install
Windows
Download the Windows Installer exe for your preferred version from the releases page. Both x64 and arm64 installers are published — pick the one matching your CPU.
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For convenience there is also a portable build available.
Troubleshooting
- If you have troubles to run the build, you might need to install following runtimes:
- MicrosoftEdgeWebView2RuntimeInstallerX64
- vcredist2019_x64
- Alternative Download Link Hosted by Microsoft
- This file may already be available on your computer if you've installed visual studio. Check the following location:
%VCINSTALLDIR%Redist\MSVC\v142
Microsoft Store
Install from the Microsoft Store when you prefer a Store-signed package (helps on Windows 11 Smart App Control).
Windows Package Manager
winget install --id=SoftFever.OrcaSlicer -e
Mac
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Download the universal DMG, which runs on both Apple Silicon and Intel Macs.
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Drag OrcaSlicer.app to Application folder.
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If you want to run a build from a PR, you also need to follow the instructions below:
Quarantine
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Option 1 (You only need to do this once. After that the app can be opened normally.):
- Step 1: Hold cmd and right click the app, from the context menu choose Open.
- Step 2: A warning window will pop up, click Open
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Option 2: Execute this command in terminal:
xattr -dr com.apple.quarantine /Applications/OrcaSlicer.app -
Option 3:
- Step 1: open the app, a warning window will pop up
- Step 2: in
System Settings->Privacy & Security, clickOpen Anyway:
- Step 1: open the app, a warning window will pop up
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Homebrew Cask
brew install --cask orcaslicer
The Homebrew cask installs the official macOS DMG from GitHub Releases.
Linux
Flathub (Recommended)
OrcaSlicer is available through FlatHub:
Install from the command line:
flatpak install flathub com.orcaslicer.OrcaSlicer
flatpak run com.orcaslicer.OrcaSlicer
It can also be installed through graphical software managers (KDE Discover, GNOME Software, etc.) when Flathub is enabled. Search for OrcaSlicer in your software center.
AppImage
AppImages are published for both x86_64 and aarch64 (ARM64). Pick the file matching your CPU — the ARM64 build has aarch64 in its name (e.g. OrcaSlicer_Linux_AppImage_Ubuntu2404_aarch64_*.AppImage).
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Download App image from the releases page.
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Double click the downloaded file to run it.
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If you run into trouble executing it, try this command in the terminal:
chmod +x /path_to_appimage/OrcaSlicer_Linux.AppImage
How to Compile
All updated build instructions for Windows, macOS, and Linux are now available on the official OrcaSlicer Wiki - How to build page.
Please refer to the wiki to ensure you're following the latest and most accurate steps for your platform.
Klipper Note
If you're running Klipper, it's recommended to add the following configuration to your printer.cfg file.
# Enable object exclusion
[exclude_object]
# Enable arcs support
[gcode_arcs]
resolution: 0.1
Supports
OrcaSlicer is an open-source project, and we're deeply grateful to all our sponsors and backers.
Their generous support helps fund filaments and other essential 3D printing materials for the project.
Thank you! :)
Sponsors
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Backers:
Ko-fi supporters ☕: Backers list
Support the project
Some Background
Open-source slicing has always been built on a tradition of collaboration and attribution. Slic3r, created by Alessandro Ranellucci and the RepRap community, laid the foundation. PrusaSlicer by Prusa Research built on Slic3r and acknowledged that heritage. Bambu Studio in turn forked from PrusaSlicer, and SuperSlicer by @supermerill extended PrusaSlicer with community-driven enhancements. Each project carried the work of its predecessors forward, crediting those who came before.
OrcaSlicer began in that same spirit, drawing from BambuStudio, PrusaSlicer, and ideas inspired by CuraSlicer and SuperSlicer. But it has since grown far beyond its origins. Through relentless innovation — introducing advanced calibration tools, precise wall and seam control, tree supports, adaptive slicing, and hundreds of other features — OrcaSlicer has become the most widely used and actively developed open-source slicer in the 3D printing community. Many of its innovations have been adopted by other slicers, making it a driving force for the entire industry.
The OrcaSlicer logo was designed by community member Justin Levine.
License
- OrcaSlicer is licensed under the GNU Affero General Public License, version 3.
- The GNU Affero General Public License, version 3 ensures that if you use any part of this software in any way (even behind a web server), your software must be released under the same license.
- OrcaSlicer includes a pressure advance calibration pattern test adapted from Andrew Ellis' generator, which is licensed under GNU General Public License, version 3. Ellis' generator is itself adapted from a generator developed by Sineos for Marlin, which is licensed under GNU General Public License, version 3.
- The Bambu networking plugin is based on non-free libraries from BambuLab. It is optional to the OrcaSlicer and provides extended functionalities for Bambulab printer users.