Google Summer of Code/Project Ideas

If you want to work on computer-aided design (CAD), geometry, or graphics, you've come to the right place! Help us improve open source CAD.

Well prepared proposals from capable students have an outstanding chance of getting selected. We consider proposals for all skill levels ranging from simple to crazy hard and everything in between. Introduce yourself, and we'll help you plan one right for you.

Remember that project descriptions are just initial ideas. You must expand with considerably more detail. Change the goals to fit your experience and interests. See our checklist to get started.

This year, BRL-CAD is coordinating with five other communities that will get 1-2 students each to help bridge our work and encourage collaboration. Projects that help exchange data or share code are desired!

BRL-CAD: 3D solid modeling, geometry processing, and robust high-performance ray tracing. Help us make a better CAD system.	OpenSCAD: rich syntax, programmable geometry. Lots of possibilities to make it interoperate with BRL-CAD and LibreCAD.	LibreCAD: specializes in 2D CAD modeling, drafting, drawings. Help build a bridge to BRL-CAD or add STEP support.
STEPcode: file format on steroids, STEP is a complex standard for geometry used by nearly every pro CAD system.	Slic3r: toolpath/G-code generator for 3D printers.	FreeCAD: parametric 3D modelling with strong Python interface and general engineering functionality like FEM and CAM

Project titles link to a page with more details.

BRL-CAD Projects

High Priority Topics

	Languages	Difficulty	Contacts
Convert MGED from Tk to Qt: Transition BRL-CAD's graphical applications from the Tk toolkit to the Qt toolkit.	C/C++/Tcl/Qt	HARD	Rossberg, Yapp
Annotations: Implement support for 2D annotations, labels that can be added to geometry.	C/C++	MEDIUM	Morrison, Yapp

Web Development

	Languages	Difficulty	Contacts
Benchmark Performance Database: BRL-CAD's Benchmark has been used for two decades to compare performance across configurations. Build a database website.	Depends (likely PHP or Python)	EASY	Morrison
Synchronize Wiki with Docbook: We use Docbook for most of our user documentation but find editing a wiki page much easier to use. Set up a system so the two are always in sync.	Depends (likely PHP or Python)	MEDIUM	Yapp
Online Geometry Viewer Interface: Continuation of existing work, improve our interface for viewing geometry online. Focus on the front-end usability.	Depends (likely PHP or Python)	MEDIUM	Morrison
Online Geometry Viewer Back-end: Continuation of existing work, improve our interface for viewing geometry online. Focus on the back-end infrastructure.	Depends (likely PHP or Python)	HARD	Morrison
Mediawiki 3D Geometry Extension: Write an extension for Mediawiki that will visualize our .g files. Maybe leverage LLVM C->Javascript translation.	Depends (likely PHP or Python)	HARD	Morrison
Materials Database: Create a Materials Database web site for collecting, managing, and providing programmatic interfaces to material properties.	Depends (likely PHP or Python)	MEDIUM	Morrison, Yapp

Geometry

	Languages	Difficulty	Contacts
NURBS Editing Support: BRL-CAD doesn't currently have support for editing NURBS primitives. Fix that.	C/Tcl	MEDIUM	Yapp
Overlap tool: Resolving geometric interferences (aka overlaps) is a common geometry editing activity. Design an awesome GUI for resolving conflicts.	Tcl	EASY	Yapp, Morrison, Greenwald
Vector Drawings from NURBS: Huge impact here if you can update one or more of our raytracers to provide vector output instead of raster. Perhaps render directly to PDF or SVG.	C and/or C++	EASY	Rossberg
NMG Editing: Our structured polygonal mesh geometry (N-Manifold Geometry = NMG) is a common export format, but our NMG edit support is non-existent. We need something.	C	HARD	Morrison, Rossberg
Visualizing Constructive Solid Geometry (CSG): CSG forms a directed acyclic graph. Tree view widgets show a simple hierarchical representation, but we need something better.	C/C++	EASY	Morrison
Plate Mode NURBS raytracing: Imported NURBS geometry often does NOT enclose space (i.e., not solid), so add support for specifying an implicit thickness.	C/C++	HARD	Morrison
STEP exporter: We have an importer, we need a comprehensive exporter with support for implicit CSG, NURBS, or polygonal mesh geometry.	C/C++	EASY	Yapp, Morrison
STEP importer improvements: We have an importer, but it's preliminary. Add support for importing hierarchy information, polygonal geometry, and implicit geometry.	C/C++	MEDIUM	Yapp
STEP AP 242 Parser: We already parse a subset of AP203, but the new kid on the block is AP242. Make AP242 work with BRL-CAD's step-g importer.	C++	HARD	Mark, Charlie, Yapp, Kamga
Convert BoT to Pipe: Command line interface to convert facetted fluid/electrical line geometry into BRL-CAD native pipe solids.	C/C++/Tcl	MEDIUM	Morrison
IGES import improvements: We have extensive support for the International Geometry Exchange Standard (IGES) with our g-iges and iges-g converters, but they need updating.	C	MEDIUM	Morrison
Geometry Conversion Library: Probably our biggest open source asset is our extensive collection of importers and exporters. Turn them all into a universal conversion library.	C/C++	EASY	Greenwald, Morrison, Rossberg
COLLADA Importer: Create an importer for the COLLADA file format.	C/C++	MEDIUM	Morrison
X3D Importer: Create an importer for the X3D file format.	C/C++	MEDIUM	Morrison, Kamga
OpenSCAD Importer: Create an importer for OpenSCAD's format.	C/C++	EASY	Morrison
OpenSCAD Exporter: Create an exporter for OpenSCAD's format.	C/C++	EASY	Morrison
Python Geometry: Wrap BRL-CAD's primitives in Python, make it easier to script geometry creation.	Python	Easy	Morrison
Perl Geometry: Wrap BRL-CAD's primitives in Perl, make it easier to script geometry creation.	Perl	Easy	Browder

Performance & Quality

	Languages	Difficulty	Contacts
OpenCL GPGPU Raytracing: We have about a dozen simple primitives that need to have a ray-object intersection function converted from C to OpenCL.	C/OpenCL	EASY	Morrison
OpenCL GPGPU Complex Raytracing: We have about half a dozen complex primitives that need to have a ray-object intersection function converted from C to OpenCL.	C/OpenCL	MEDIUM	Morrison
OpenCL GPGPU Spatial Partitioning Raytracing: We use a Bounding Volume Hierarchy (BVH) to reduce the amount of intersections we need to compute to render an image. We need to replace this with a Kd-tree in order to be able to early terminate a render in models with high depth complexity. This should speed up render speed significantly for those models (e.g. Goliath).	C/OpenCL	HARD	Morrison
Coherent Raytracing: Our current raytrace pipeline dispatches and processes one ray at a time. Send bundles and convert the pipeline into phases.	C/C++	MEDIUM	Morrison, Rossberg
NURBS Booleans: We have NURBS surface-surface intersections working. Now we're using them to create evaluated forms of our CSG geometry. Make it more robust and faster.	C/C++	HARD	Yapp, Rossberg
NURBS Optimization and Cleanup: We have a fantastic implementation of NURBS evaluation but haven't gone back to clean up or speed it up. Make it pretty and fast.	C/C++	MEDIUM	Yapp, Morrison
Fix Bugs: We take pride in our breadth of functionality and time-tested stability. We still have bugs. Identify some and fix them!	C	EASY	Browder
NMG Raytracing Performance Improvement: BRL-CAD's structured mesh geometry (N-Manifold Geometry = NMG) needs some time in a profiler. Malloc during raytracing is bad.	C	HARD	Morrison, Greenwald
Mesh library cleanup: BRL-CAD has an extensive n-manifold polygonal mesh library that needs some refactoring, testing, and optimization rework.	C	MEDIUM	Morrison, Rossberg
Space Partitioning for Tessellation: Technically an optimization task, make our geometry converters run an order of magnitude faster by using spatial partitioning during tessellation.	C	HARD	Greenwald, Yapp, Morrison
Code Reduction: BRL-CAD is more than 1M lines of code. Approximately 10% of that is duplication. Help reduce that percentage.	C	EASY	Greenwald, Morrison
Header Restructuring: BRL-CAD has about two dozen libraries with a single header declaring the entire public API. Break up those monster headers into modular sub-headers.	C	EASY	Greenwald, Morrison
Faster Overlap Detection: BRL-CAD has a 'gqa' tool that detects overlaps. Implement a replacement using a better approach.	C	MEDIUM	Greenwald, Morrison

Infrastructure

	Languages	Difficulty	Contacts
New Cross-Platform 3D Display Manager: BRL-CAD uses display managers for visualizing 3D geometry in a window. We want one that uses a cross-platform toolkit such as Qt + OGRE.	C/C++	MEDIUM	Morrison
New Cross-Platform 2D Framebuffer: BRL-CAD uses framebuffers to display 2D imagery. The merits of having a single interface for most platforms is self-evident.	C/C++	EASY	Morrison, Yapp
Advanced Sketch Primitive Editor: BRL-CAD has a 2D sketch primitive, but our handling of editing sketches doesn't incorporate parametric constraints. There are potentially applicable codes in the open source community we can leverage for this, or we can roll our own solution.	C/C++	MEDIUM	Yapp
Geometric Constraint Solver: Our LIBPC parametric constraint library is the work-in-progress foundation of being able to validate and describe geometry relationships.	C/C++	HARD	Morrison
MGED to Archer Command Migration: Our next-generation editor (Archer) needs to have the same (700+) commands that are in MGED. Help make our next CAD interface awesome.	C and Tcl	EASY	Yapp, Kamga
General Tree Walker: We have a half dozen or more functions that will traverse a geometry hierarchy in different ways. There only needs to be one.	C	EASY	Greenwald, Yapp, Morrison
Consolidate image processing: We have 100+ image processing tools that independently read and write file data. Needs much reuse love.	C	EASY	Greenwald, Daga
GED Transactions: Migrating functionality from our MGED geometry editor into our LIBGED library provided excellent code reuse, but now we need transactions so that actions can be undone.	C	EASY	Morrison, Daga
Add exec option to search: Our LIBGED library provides a search command very similar to the UNIX find command for scanning through geometry. Implement the -exec option.	C	EASY	Yapp, Daga
Geometry Selection Functionality: Implement a new selection command that lets you temporarily group objects based on spatial, attribute, or geometric properties.	C	EASY	Morrison
Astronomical units: We already go "big", but accurately modeling at a galactic scale redefines that notion...	C	EASY	Morrison, Greenwald, Daga
Object-oriented C++ Geometry API: Extend our C++ library which provides a simple interface to BRL-CAD's core functionality. Kickstart start a new geometry kernel.	C++	MEDIUM	Rossberg, Kamga
Point Clouds: BRL-CAD has a basic point cloud primitive. Beef it up, make it faster, maybe integrate with the Point Cloud Library (PCL) for evaluation.	C/C++	MEDIUM	Browder, Kamga
Annotations: Implement support for 2D annotations, labels that can be added to geometry.	Perl	EASY	Browder
Python Bindings: With or without SWIG, wrap BRL-CAD's command library API so you can issue our creation and editing commands from Python.	Python	EASY	Morrison
Perl Bindings: With SWIG, wrap BRL-CAD's ray-tracing library API so you can issue calls to librt ray-tracing functions from Perl.	Perl	EASY	Browder, Daga

Rendering & Scientific Analysis

	Languages	Difficulty	Contacts
Shader Enhancements: We have a functioning custom shader system in BRL-CAD, but there are now folks that specialize and there's lot of room for improvements.	C	EASY	Morrison, Greenwald
Material and Shader Objects: This one is a biggie but easy. Implement new object entities for describing shaders and material properties, use them during ray tracing.	C	EASY	Morrison
GUI Integration of Analysis Tools: There are a lot of visualization tools in BRL-CAD, but most aren't integrated with the GUI. Visualizing directly within the GUI would improve usability.	C	MEDIUM	Rossberg
Generalized abstracted spacial partitioning capability: Need more be said? If you're familiar with BSPs, KD trees, and grid structures, then this one is for you.	C	HARD	Greenwald, Morrison
High Dynamic Range Support: We don't have displays supporting this yet, but that's never stopped us before. Implement support for images with more than 8-bits per channel.	C and/or C++	EASY	Greenwald, Yapp
Analysis Library: There are various tools in BRL-CAD for calculating weights, moments of inertia, and more. They're stand-alone applications. Turn them into a library.	C	HARD	Yapp, Morrison
Celestial mechanics particle system: Simulate solar systems and galaxies.	C/C++	MEDIUM	Greenwald
Non-vacuum gravity simulator: Simulate falling to earth.	C/C++	MEDIUM	Greenwald, Morrison, Yapp
Polarization: We already do multispectral ray tracing, but don't simulate polarization effects. Implement ray splitting and filtering.	C	HARD	Morrison, Rossberg
Density functions: Accurately represent everything from atmosphere to bone. Implement support for parametric density functions for homogenous materials.	C	HARD	Rossberg, Morrison
Bending light: Think gravity wells and satellite cameras.	C	MEDIUM	Morrison
Appleseed renderer integration: Appleseed is rendering infrastructure used by the film industry to make pretty pictures. Make it shoot rays at our native geometry with our ray trace library.	C	MEDIUM	Morrison

<An Idea of Your Own>

Do you have an idea of your own? Maybe you need more ideas to inspire you? We're very open to areas of academic research, industry applications, and ideas that get you hooked on open source CAD development.

Requirements:

• Passion for the task being suggested

OpenSCAD Projects

OpenSCAD is a parametric solid 3D modeling tool which uses a Domain Specific Language to specify designs as plain text. It is specifically designed with 3D printing in mind.

	Languages/Tools	Difficulty	Contacts
Improve DXF Import and Export: Look into using an external library for DXF import (and export?).	C++	MEDIUM	Marius/Torsten
OpenSCAD Standard Library: Create a standard user-space OpenSCAD library.	OpenSCAD	MEDIUM	Marius/Torsten
OpenGL framework: Rewrite the OpenGL rendering code to use a rendering framework. Focus on compatibility with OpenGL ES2 and rendering performance.	C++ OpenGL	MEDIUM	Marius/Torsten
Persistent Caching: Implement a disk-based version of the internal memory caches	C++	MEDIUM	Marius/Torsten
Multi-threaded Geometry Evaluation: Implement multi-threaded evaluation of geometry.	C++	MEDIUM	Marius/Torsten
Survey of CSG algorithms: Review existing research, evaluate and prototype algorithms.	C++	MEDIUM-HARD	Marius/Torsten
Issue Handling: Day-to day issue and community management, fix incoming and existin issues. Good place to get started.	C++	EASY	Marius/Torsten
Test Framework Improvements: Improve tests and test framework. Good place to get started.	C++	EASY-MEDIUM	Marius/Torsten
SVG Import: Improve/finalize SVG import.	C++, SVG	MEDIUM	Marius/Torsten
Larger tasks for particularly experienced people: Various harder tasks which are not fully specified and requires significant effort to design and implement.	C++	HARD	Marius/Torsten

The OpenSCAD team is also open to new ideas. Please get in touch to discuss your ideas and convince a mentor to back it.

LibreCAD Projects

LibreCAD is a free Open Source CAD application for Windows, Apple and Linux. Support and documentation is free from our large, dedicated community of users, contributors and developers. Please refer to LibreCAD GSoC 2018 ideas for more detailed description.

	Languages	Difficulty	Contacts
LibreCAD 3 UI: Add missing features, e.g. snapping, to the very basic GUI.	C++,Math	MEDIUM	Armin, Florian
LibreCAD 3 DXF Entities Implement missing DXF entities, e.g. blocks, use LibreCAD 2 for reference.	C++,Math	MEDIUM	Armin, Florian
LibreCAD 3 OpenGL rendering: Replace our current rendering engine Cairo with pure OpenGL rendering.	C++	MEDIUM/HIGH	Armin, Florian
LibreCAD 3 Plugin Interface Right now we have some LUA based scripting support for LibreCAD 3. But we want to be much more extensible, e.g. with a XML/JSON interface.	C++	MEDIUM/HIGH	Armin, Florian
LibreCAD 3 trimming support LibreCAD 3 trim operation doesn't support all entities and is entirely written in Lua. We need a better system which would support all entities and divide operation.	C++,Math	MEDIUM	Armin, Florian

STEPcode Projects

	Languages	Difficulty	Contacts
STEP Coverage Test: Write a program that links against STEPcode and generates a STEP output instantiating every entity for a given schema. Goal is a comprehensive program and data file for testing STEP import/export.	ANY (C/C++, Python, Java, Perl, ...)	EASY	Mark, Charlie
STEP Incremental Loading: Basically take a work-in-progress to the next level. Modify the STEP parser to only read what it needs when it needs it, test, clean up, profile, and optimize.	C++	EASY	Mark, Charlie
STEP Minimal Examples: Create minimal examples for various schemas - such as AP214 or AP242 - in the style of ap203min	C++	MEDIUM	Mark, Charlie
STEP Multiple Protocol Parsing: Currently creates a parser that works with a specific application protocol (e.g., AP203, AP214). Make it work with multiple simultaneously.	C++	MEDIUM	Mark, Charlie
STEP Source Code Documentation: We already use doxygen, but could do much better. Improve code documentation and utilize additional doxygen features such as topic pages. Add a 'make doxygen' target to invoke doxygen.	C/C++	EASY	Mark, Charlie
STEP EXPRESS Documentation: Write 'exp2html', similar to exp2py or exp2cxx (python and C++ generators) but outputs graphs and hyperlinked documentation with JavaScript search. Output will include EXPRESS comments (this requires modifying the parser).	C/C++, JavaScript	MEDIUM	Mark, Charlie
STEP Viewer: STEP is a common CAD file format supported by just about every major CAD system. Given we have an importer and an interface for displaying geometry, a stand-alone STEP file viewer has some great potential.	C/C++	MEDIUM	Mark, Charlie
STEP Code Refactoring: Split large files and functions, add unit tests, move contents of LISTdo loops into separate functions.	C/C++	EASY	Mark, Charlie
STEP Thread Safety and Performance: Modify the libraries to improve thread safety, increase performance using hotspot analysis	C/C++	MEDIUM	Mark, Charlie

Slic3r Projects

Slic3r is CAM desktop application for toolpath/G-code generation for 3D printers.

	Languages	Difficulty	Contacts
Conditional G-code and arithmetic expressions parser: Implement a grammar parser for conditional and arithmetic expressions within custom G-code, maybe using Boost.Spirit or some other library. #3390	C++	Easy-Medium	Alessandro/Joseph
Port the GUI to C++: The GUI is currently coded in Perl using wxWidgets and our goal is to have it ported to C++. The wxWidgets API is almost identical between Perl and C++, so it's an easy task. There are a couple things where we use the dynamic features of Perl which are trickier and interesting to port.	C++/wxWidgets	Easy	Alessandro/Joseph
Port the SVGNest library to C++: The SVGNest library provides an algorithm for polygon nesting. It's written in JavaScript and a C++ port of it would improve Slic3r's auto-arrange feature. #3237	C++	Easy	Alessandro/Joseph
Fix bugs of the Boost.Voronoi library: The good but unmaintained Boost.Voronoi library has a couple minor issues affecting Slic3r's results. Interesting task for learning the Voronoi algorithm and how to troubleshoot a computational geometry issue. #2948	C++	Medium	Alessandro/Joseph
Wireframe printing: Implement the wireframe printing algorithm. #2274	C++	Medium	Alessandro/Joseph
Automatic part rotation: Automatically rotate a part to make some face of the part the bottom. #3047	C++	Medium	Alessandro/Joseph
Manual support creation: Allow users to place and move support pillars by clicking in the 3D GUI. #3062	C++/Perl/OpenGL	Medium/Hard	Alessandro/Joseph
Refactor the TriangleMesh class and support non-solid walls: Replace the internal mesh representation (currently based on admesh) using an existing 3D mesh library or implementing a half-edge structure; only use admesh for fixing models. Keep non-solid walls and slice them as single paths. Bonus: import SVG paths and position them freely using the GUI for printing as single extrusions. #3560 #3523	C++	Medium/Hard	Alessandro/Joseph
Implement 3MF format read/write: Add the 3MF format for both reading and writing. #2811	C++	Easy	Alessandro/Joseph
Non-planar printing: Implement techniques for non-planar printing. #3442	C++	Medium	Alessandro/Joseph
Support surface colors and mixing extruders: Read surface colors from AMF or OBJ and keep them throughout the slicing process in order to generate G-code for mixing extruders. #3546	C++/Perl	Hard	Alessandro/Joseph
Clean the libslic3r API and write bindings for it: Expose the internal algorithms of Slic3r as a library and write bindings for Python, Perl etc.	C++/any	Easy	Alessandro/Joseph
Write a Slic3r plugin for Grasshopper: Expose Slic3r functionality as many separate components that can be plugged in larger GH definitions (for example: slice a NURBS model in GH and feed the slices to the toolpath generation process in order to skip mesh generation, or provide flow calculation for people driving 5-axis robots with custom motion). This requires a fair amount of design work.	C++	Medium/Hard	Alessandro/Joseph

FreeCAD Projects

	Language	Difficulty	Contact
Advanced FreeCAD test system : Create a framework for result file based comparisons and workbench specific comparators. Also creation of test cases should be simplified by a GUI or wizard.	Python/C++	Medium	Ickby
Topological Naming Project: Implementation of subshape identifiers based on creation history and update of topology class to work with those identifiers.	C++	Hard	Ickby
Direct modeling tools: Create a new layer of tools and objects, that work on top of existing Part-based 3D objects, that allow a user to graphically modify their geometry.	Python/C++	Medium	Yorik
FEM Post Processing based on VTK: Base the existing FEM VTK post processing on the updated SMESH data structure and design a python interface for it. Also improve integration into the workbench.	C++	Medium	Ickby
IPython notebook integration: Create a way to export the open inventor scenegraph as a JavaScript file and add functions for seamless interaction with the IPython display system	C++, JavaScript, Python	Easy	Ickby
Integrate Cycles renderer: Add Blender's new Cycles renderer as a new render engine to the Raytracing Workbench	C++	Medium	Yorik
Stepwise integration of ElmerFem into FreeCAD should be done in three phases: Phase 1 - New solver object for handling ElmerFEM execution in FEM-workbench. Phase 2 - Mapping of main ElmerSolver setting for mechanical simulations. Phase 3 - Give graphical access to a wide range of available ElmerSolver setting from within FreeCAD	Python/C++	Medium-Hard	Bernd, HoWil
PartDesign Updates: Finish PartDesign port to new Body object, simplify the workflows and extend tools while making them more robust.	C++, Python	Medium	Ickby
GSoC FEM Solver Z88: Extend the capabilities of FEM solver Z88OS in FreeCAD FEM workbench.	Python	Easy-Medium	Bernd
GSoC FEM Unit Tests: Extend the unit tests of FreeCAD FEM workbench.	Python	Easy-Medium	Bernd
GSoC Path/Robot Integration: Path is the CNC/CAM workbench. It currently lacks any simulation capability. Robot workbench is a tool for simulating industrial robots. Extend Path and Robot workbenches to support simulation of CNC operations in the Robot workbench.	C++, Python	Easy-Medium	Yorik, sliptonic

Mentors

BRL-CAD operates under group mentorship. That means you can contact anyone, not just the person assigned to you, for assistance. The mailing list and IRC channel are the preferred communication methods.

• Christopher Sean Morrison
  • brlcad on irc.freenode.net
  • Org admin, BRL-CAD open source project lead

• Erik Greenwald
  • ``Erik on irc.freenode.net
  • Org admin, BRL-CAD core dev

• Cliff Yapp
  • starseeker on irc.freenode.net
  • BRL-CAD Mentor, core dev

• Daniel Rossberg
  • d_rossberg on irc.freenode.net
  • BRL-CAD Mentor, core dev, math expert

• H.S. Rai
  • hsrai on irc.freenode.net
  • BRL-CAD Mentor, math expert

• Tom Browder
  • BRL-CAD Mentor, analysis expert

• Bryan Bishop
  • BRL-CAD Mentor, python guru

• Isaac Kamga
  • Izakey on irc.freenode.net
  • BRL-CAD Mentor, C/C++ Programmer

• Mohit Daga
  • zero_level irc.freenode.net
  • BRL-CAD Mentor, Computer Science Engineer

• Mark Pictor
  • mpictor on irc.freenode.net
  • STEPcode Mentor

• Charlie Stirk
  • cstirk
  • STEPcode Mentor

• Marius Kintel
  • kintel on irc.freenode.net
  • OpenSCAD Mentor

• Torsten Paul
  • teepee on irc.freenode.net
  • OpenSCAD Mentor

• Armin Stebich
  • LordOfBikes on irc.freenode.net
  • LibreCAD Mentor

• Florian Roméo
  • Feragon on irc.freenode.net
  • LibreCAD Mentor

• Alessandro Ranellucci
  • Sound on irc.freenode.net
  • Slic3r Mentor

• Joseph Lenox
  • LoH on irc.freenode.net
  • Slic3r Mentor