The Engineer's Slicer

preFlight is an advanced 3D printing slicer built for precision and performance. Building on the Slic3r legacy as a spiritual successor to PrusaSlicer, it offers exclusive features and a comprehensive under-the-hood overhaul, bringing the entire dependency stack up to modern standards. Given this massive modernization, preFlight has evolved beyond the constraints of the original codebase, making upstream merging irrelevant.

Based in Georgia, USA, oozeBot is a small but ambitious team currently preparing for the take-off of our Elevate line of 3D printers. preFlight is the cornerstone of the ecosystem we are building - a genuinely new option in the 3D printing space designed to benefit all makers, regardless of the hardware they use.

Want to see what makes preFlight special? Head over to our Feature Showcase to view screenshots, learn more about unique features, and join the discussion.

While preFlight is open-source and free for everyone, your support helps us maintain the infrastructure, fund R&D, and keep our team in orbit. If you find value in our tools, consider contributing to the mission.

Support the preFlight Mission (via Stripe)

Windows and Linux. macOS support coming soon.

Windows: Microsoft Visual C++ Redistributable (x64) - Install this first if preFlight won't launch.

Linux: Download the AppImage from GitHub Releases, make it executable (chmod +x), and run. No installation required.

To ensure the integrity of your installation and protect yourself, please following these security guidelines:

• Official Downloads: Only download preFlight binaries directly from our GitHub Releases page. We do not distribute preFlight through third-party mirror sites.
• Verified Signature: All official Windows binaries are digitally signed by oozeBot, LLC using an Organization Validation (OV) Code Signing Certificate.
• Verification: Before running the installer, right-click the file, select Properties, and navigate to the Digital Signatures tab. Ensure the "Name of signer" is explicitly listed as oozeBot, LLC.
• Safety First: If you receive a "Windows protected your PC" (SmartScreen) warning on a file that is not signed by oozeBot, LLC, do not proceed with the installation and report the issue immediately.

In Greek mythology, Athena defeated Arachne not through greater complexity, but through discipline and precision. We named our perimeter generator after her for the same reason.

Why Athena Exists

We forked Arachne to modernize it in several ways. Athena uses fixed extrusion width instead of variable and independent overlap control between perimeters. Arachne calculates overlap automatically. Athena lets you specify exactly how much perimeters overlap. It even enables negative overlap for creating gaps between perimeters.

• Positive overlap: Perimeters merge into each other (stronger bonding)
• Zero overlap: Perimeters just touch
• Negative overlap: Gap between perimeters (useful for flexible or soft materials)

• Fixed extrusion widths with variation absorbed in spacing, not width
• Predictable wall shell thickness
• Full thin wall support

When to Use Athena: You need control over how perimeters bond, want consistent external perimeter width, or are tuning for strength/flex behavior.

When to Use Arachne: You prefer automatic overlap calculation or don't care about perimeter spacing.

A novel approach to layer bonding using spacing variation and compression bonding - fundamentally different from "brick layers".

How it works:

• Alternates perimeter spacing between layers (X/Y axis manipulation)
• Over-extrusion compresses material into horizontal gaps
• Creates diagonal bonding surfaces as material compresses into gaps
• All beads printed at constant layer height (no Z-axis manipulation)

Key distinction from "brick layers":

Benefits:

• 5-15% strength increase (estimated)
• No material or time penalty at 100% strength
• Maintains dimensional accuracy (constant layer heights)
• Requires Athena perimeter generator

64-bit coordinate types throughout.

// PrusaSlicer/OrcaSlicer/SuperSlicer:
using coord_t = int32_t;  // Overflow risk

// preFlight:
using coord_t = int64_t;  // No overflow, native Clipper2

Why it matters:

• 32-bit coords overflow in cross products with large coordinates
• Clipper2 uses 64-bit internally - type mismatch causes bugs
• Large print volumes can exceed 32-bit range

Zero temp files during slicing:

• No disk I/O during slicing
• ~50% less RAM (no per-line string overhead)
• Faster slicing (no file system operations)

Mixed support types on a single object.

• Paint Snug (Blue) - Strong, close contact
• Paint Grid (Orange) - Balanced strength/removal
• Paint Organic (Green) - Easy removal, delicate areas

Strong supports under critical overhangs, easy-to-remove supports elsewhere. All on one print.

• Draw straight seam lines between points instead of painting freehand. Perfect for placing seams along edges or in straight grooves. Includes Z-axis snapping (within 5°) for vertical lines.
• Minimum brush size reduced to 0.1mm

Intelligent perimeter ordering eliminates crossing travel paths:

• Centroid-based starting position for better initial grouping
• 2-opt optimization algorithm to eliminate crossing travel paths
• Adaptive iteration count scaling with group complexity

Intelligent print ordering minimizes travel:

• Interlocking perimeters build containment tree
• Concentric fill uses depth-first traversal
• Sparse infill uses union-find clustering
• 30-50% reduction in travel distance for gyroid on multi-island layers

Direct RRF integration for automatic machine limit configuration.

One-click retrieval of all machine limits directly from Duet/RRF printers:

• M566 (Jerk), M201 (Acceleration), M203 (Feedrate)
• M204 (Print/travel accel), M207 (Firmware retract)

• Junction Deviation support (Marlin M205 J)
• RepRapFirmware acceleration model
• Print time estimates that actually match reality

"Max cmd/s" column shows:

• Maximum commands per second for each extrusion role
• Which layer the maximum occurred on
• Identify bottlenecks before printing

Interactive G-code exploration for troubleshooting and analysis.

Mouse Wheel Scrubbing: Hover over the G-code window and scroll to scrub through commands in real-time. The 3D preview updates as you scroll, letting you pinpoint exactly which command produces which movement. Right-click any G-code command to instantly copy to your clipboard.

Additional Features:

• Keyboard arrow navigation (command-by-command)
• Right-click to copy any command to clipboard
• Width matched to legend for clean UI

• Top Surface Flow Reduction - Reduce flow on top layers for smoother finish
• Narrow Solid to Concentric - Automatically switch to concentric pattern when solid areas are too narrow for rectilinear
• Bridge Infill Overlap - Independent control over overlap between bridge extrusions

• Always-Synced Support Layers - Support layers perfectly align with object layers (no fractional heights)
• Variable Interface Layer Heights - Achieve desired gap through interface height adjustment, not Z-offset
• Simplified Bottom Contact - Clear options: No Gap, Half Layer, Full Layer (instead of arbitrary mm values)

• Full Manual Fan Control - Complete manual cooling control for each feature type
• Fan Spin-Up Options - Configure fan spin-up timing for precise cooling with overhang perimeters and bridge infill
• Wipe Enhancements - Improved wipe/retraction behavior

• Layer 0 Preview - See blank build plate before first extrusion
• Preview Slider Accelerators - Ctrl (2x), Shift (4x), Ctrl+Shift (8x) navigation
• Settings Tab Auto-Commit - Click dead space to commit fields
• Progressive Slicing Feedback - Visual feedback during slicing
• Solid Fill Pattern Selection - Choose pattern for internal solid layers

Ported from OrcaSlicer with enhancements:

• Per-ear overlap control (-100% to +100%)
• Always-visible rendering
• Full undo/redo support

Ported from OrcaSlicer with enhancements

Noise Types:

Advanced Controls:

• Visibility Detection - Optional skip fuzzy on top-visible surfaces
• Bottom Detection - Optional skip fuzzy on bottom layers - always skip overhangs
• Per-Perimeter Control - Limit fuzzy to external perimeters only
• Point placement - Standard or Shape following
• Fuzzy skin mode - Displacement, Extrusion, Combined
• Scale - Feature size in mm
• Octaves - Detail levels (noise complexity)
• Persistence - How much each octave contributes

• GMP/MPFR - CGAL 6.x uses Boost.Multiprecision instead
• OpenCSG - Dead/unused code removed
• GLEW - Replaced with actively maintained GLAD

• C++20 compilation
• Memory leak fixes (gigabytes saved over long sessions)
• CMake 4.x ready

preFlight works with any modern 3D printer accepting RepRap-flavored G-code:

• Marlin firmware
• Prusa firmware
• RepRapFirmware (Duet)
• Klipper
• Smoothieware

• Input: STL, OBJ, 3MF, AMF, STEP
• Output: G-code for FFF printers

Requires Visual Studio 2026 (VS 2022 is not supported)

# Build dependencies (first time only)
build_win.bat -STEPS deps

# Build release
run_build.bat -ninja

# Build debug (for development)
run_build.bat -ninja -debug

Build Options:

# Build dependencies (first time only)
./build_deps.sh

# Build release
./build_linux.sh

# Package as AppImage
./pack_appimage.sh

Not yet available.

Coming soon.

preFlight is licensed under the GNU Affero General Public License, version 3. See LICENSE for details.

preFlight is based on PrusaSlicer by Prusa Research, which is based on Slic3r by Alessandro Ranellucci and the RepRap community.

• Email: support@ooze.bot
• GitHub Issues: github.com/oozebot/preFlight/issues

preFlight - Precision where it matters.