Open CASCADE Technology is also a backbone of many good projects. For example, FreeCAD providing parametric 3D modelling, drafting and many other capabilities is easy to use for beginners. KiCad – free 3D CAD software for PCB layouts design. Gmsh – a fast meshing tool. Salome – a platform for numerical simulation. CAD Assistant – a powerful viewer and converter. To review the projects based on OCCT, refer to the links below.