41fe55bda3
=========================================================================== Block constraint is naturally redundant/conflicting with almost any other constraint applied to an edge (certainly with constraints operating only on that element). As such, a block constraint will have very little applicability in absence of a way to handle this redundancy/conflicting. For example, in the case of a BSpline all its internal geometry (construction circles on poles and its constraints) would have to be removed before locking. This would mean that it is not possible to define the BSpline shape and then block it, as when removing the internal geometry the shape would be lost. In other cases, like temporally blocking to avoid that a part of the sketch moves while performing some operation with the idea of afterwards unblocking it, it would mean removing all constraints, to add the block constraint, then perform the action, then remove the block constraint and manually constraint it again. Handling this situation in a user expected way means ignoring certain constraints (those causing the redundancy/conflicting), so that the solver is not aware of them and does not complain. However, generally ignoring those constraints has a negative effect, in that constraints applied by the user on already blocked geometry, or constraints that otherwise lead to a conflicting or redundant situation as a consequence of actions (further constraining) after the Block constrain is applied are ignored, thereby not properly informing the user of this situation, which is undesirable. This new mechanism takes account on the position of the constraints relative to the involved blocked constraint(s). As such, redundant/conflicting constraints that were added before the Block constraint are ignored, whereas those constraints that lead to a redundant/conflicting situation and added AFTER the block constraint was already in place, those are not ignored and are reported accordingly.
FreeCAD
FreeCAD is a general purpose feature-based, parametric 3D modeler for CAD, MCAD, CAx, CAE and PLM, aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialties. It is 100% Open Source (LGPL2+ license) and extremely modular, allowing for very advanced extension and customization.
FreeCAD is based on OpenCASCADE, a powerful geometry kernel, features an Open Inventor-compliant 3D scene representation model provided by the Coin 3D library, and a broad Python API. The interface is built with Qt. FreeCAD runs exactly the same way on Windows, Mac OSX, BSD and Linux platforms.
Installing
Precompiled (installable) packages are available for Windows and Mac on the Releases page.
On most Linux distributions, FreeCAD is directly installable from the software center application.
Other options are described at the wiki Download page.
Build Status 
| Master | 0.16 | Translation |
|---|---|---|
 |
 |
 |
Compiling
Compiling FreeCAD requires installation of several libraries and their development files such as OpenCASCADe, Coin and Qt, listed in the pages below. Once this is done, FreeCAD can be simply compiled with cMake. On Windows, these libraries are bundled and offered by the FreeCAD team in a convenient package. On Linux, they are usually found in your distribution's repositories, and on Mac OSX and other platforms you will usually need to compile them yourself.
The pages below contain up-to-date build instructions:
Usage & Getting help
The FreeCAD wiki contains documentation on general FreeCAD usage, Python scripting, and development. These pages might help you get started:
The FreeCAD forum is also a great place to find help and solve specific problems you might encounter when learning to use FreeCAD.