Note: the grid shown in the screenshot above is included and enabled by default in the Constraint Design workbench
Constraint Design is an addon for FreeCAD that aims to implement a more stable alternative to the current integrated Part Design workbench. One of the most important new features that you can use with this new workbench is the Custom Element Selector, which is not directly tied to OpenCascade elements. This means that you will encounter less Topological Naming Problems (AKA Toponaming or TNP) when compared to other solutions built into FreeCAD.
The main benefit of this addon is the lack of Topological Naming Problems, as stated earlier. When making changes to parts, it is much less likely that you will have unexpected bizarre errors or changes that break your model. You can also use the Assembly 4.1 workbench with this addon out of the box (Important: changes to implement are not yet merged into upstream). This integration gives you tools to create assemblies, variant parts, basic animations, BOMs and much more. Many of the tools you see in Part Design (Note: unchecked boxes indicate pending support) are also implemented in this workbench:
- Extrude
- Part Mirror
- Loft
- Fillets
- Chamfers
- Countersinks
- Sweeps
- Revolves
- Linear Patterns
- Circular Patterns
- Feature Mirror
- many more...
Note: There are also some new features, like the Part Mirror or Derive tool, which you do not find in the main FreeCAD branch.
The only thing you select when working with ConstraintDesign Parts are boundaries generated every time you recompute the part. Each edge and most vertices (Note: loft is missing support still) have an entry into an ElementMap which contains a persistent name that does not change every time you recompute the part. The selection system references said map to find the most up-to-date OpenCascade element name which can be used safely. These element names will change every time something is added or removed from a previous sketch, but the map will update with the correct name so that there are few TNPs.
Nothing is perfect, especially not this workbench. Below are some examples of small edgecases with the Toponaming system:
- Lofts do not have perfect checks, and some renames do not work properly. I've mitigated most of the areas failure points so far, but it's not perfect.
- Sketch trimming can cause renames of geometry, which can cause some unwanted changes. I have no current plans to implement more complex checks to fix this, as it would take a long time and be rather unreliable in my opinion.
- Weird ID naming.
The speed of regeneration of these parts can take significantly longer than if the part was created in another workbench. I am working on this issue actively, since there have been some large improvements since before releasing v1.0.0 of the addon. I was able to decrease the time of generation of boundaries, for example, from 1.9 seconds or so to about 100 milliseconds. Dressups take a lot longer because they check the geometry of the OpenCascade generated shape for the right edges.
There are a LOT of bugs currently, please report them in the issues queue. Please include your full About info along with clear step-by-step instructions to reproduce the issue. Screenshots/screencasts are also very welcome.
Contributions are welcome. Please open a ticket to discuss any code contributions in advance. This significantly raises the probability of merging said code.
This workbench is released under the LGPL2.1 license.