SolveSpace
SolveSpace is a free and open-source 2D/3D constraint-based parametric computer-aided design (CAD) software that supports basic 2D and 3D modeling. It is a constraint-based parametric modeler with simple mechanical simulation capabilities. Version 2.1 and onward runs on Windows, Linux and macOS. The Linux version is shipped as a snap and native packages. It supports STEP and DFX for import and export. By default, SolveSpace utilizes its own CAD file format called for model storage. It is possible to export models as a whole or in part to various formats such as PDF, SVG, or Encapsulated  PostScript (EPS). It was initially created by Jonathan Westhues and as of 2022 is maintained by a community of volunteers. History. Development of SolveSpace started in 2008. A previous software package called SketchFlat, also developed by Westhues, was replaced by SolveSpace. In an 2020 interview article with a major maintainer named "Whitequark", SolveSpace was described as being very conservative in terms of backward compatibility. The codebase at the time was about 30,000 lines of code and it took Whitequark almost 2 years to familiarize herself with it. On September 22, 2020, Whitequark stepped down as a maintainer with the possibility  of occasional contributions. Overview. SolveSpace is free and open source software distributed under the GPL-3.0-or-later license. Features. SolveSpace is shipped with the following basic features: Supported file formats. Importing. SolveSpace can open and import its own textual file formats for both editing and assembly. The DXF/DWG file format AutoCAD (version 2007) is supported for opening and editing. Exporting. SolveSpace v3.0 is able to export 2D sketches and surfaces into DXF/DWG (AutoCAD version 2007), PDF, SVG, EPS, and HPGL file formats. Wireframes can be exported as DXF and STEP files. Polygon meshes can be exported as STL  and Wavefront OBJ; NURBS as STEP. SolveSpace is able to export models in STEP, STL, and G-code for reuse in third-party CAM software. Workflow. SolveSpace workflow starts either with opening an existing file or creating a new one and usually involves sketching. The basic shapes of a new physical part is sketched out and constrained to specific dimensions and locations. When the model is complete, it is either exported to one of the supported CAD formats or into a document for further processing. Sketching. Modeling in SolveSpace is done by way of sketching in a workplane. A workplane  is plane with an origin for the new sketch where the SolveSpace draws entities. Users can make it active and draw basic primitives such as lines, circles, arcs, dots, and other points of references on the workplane, and constrain them to specific dimensions and relations. SolveSpace can split intersecting entities via a separate tool. Users can snap points to a grid. There are no software limitations for the number of workplanes user can create. Constraints. Constraints include dimension limitation, angle, paralleling with another line, tangency, point, symmetry and alignment of a line with origin axes (to make them "vertical" or  horizontal). The radius of a circle, for instance, can be constrained to a specific value, or can be influenced by some other entity dimension. 3D modeling. When sketching is complete, a 3D part can be extruded into a volumetric model for further modeling. An extruded model creates a group along a specified normal. Every group in SolveSpace encapsulates an action applied to the specified sketch created for every 3D operation, such as an extrusion, rotation, or translation. Created 3D models can also be further constrained with the basic tools mentioned above or combined with another one by Boolean operations. It  is also possible to draw a workplane on a specific "surface" of another 3D model; the surface is usually indicated by two line segments joined by a point. Assembly. In order to verify a newly modeled concept in SolveSpace, users can "link" all the components and constrain them at specific positions to check whether the virtual end-product meets the original concept's design and constraints. Libraries. SolveSpace depends upon ANGLE, OpenGL Utility Library, zlib, libpng, libdxfrw, cairo, , mimalloc, libsigc++ and some other C++ libraries, as well as freetype2, harfbuzz, and Pango for text rendering. Linux specific libraries include gtk-3 , Gio, and X11. Limitations. As of v2.1., SolveSpace reference lists a disclaimer on limited support for NURB-surface Boolean operations which may occasionally fail. Criticism. A 2013 article and interview with the main developer published in Libre Graphics World has praised SolveSpace for its small executable file size, advanced constraints solver, and output formats. However, it was also criticized for some drawbacks it had at the time, such as limited support for NURBS (i.e. boolean operations) and a lack of native Linux support, the latter of which has since been rectified.