QCAD.org Forum

Saw this question asked in 2010 but thought it might be valuable to ask again. I've been using another cad app for my 3D printing designs and I've become quite fond of parametric constraints. Coming back to QCAD has me missing that capability quite a bit.

Unfortunately, I can only confirm that there are still no plans for parametric constraints in the foreseeable future for QCAD. While it might be interesting at some point, there are simply too many other priorities. I don't think constraints are very high on the list of what QCAD users want. It hardly ever comes up (once every 12 years ).

Existing users might not know what they're missing and there's probably no good way to determine how many *more* users you might be able to attract with parametric features but I totally understand your position. I'll ask again in 12 years!

Parametric functionality would be a game changer, but I believe it would fundamentally challenge the philosophy of QCAD as a simple to use 2D CAD option. (I have no authority on this, just making an observation based on my time here in the forum) I have to also imagine it would take some considerable backend development requiring a crew of full-time software engineers. But who knows, maybe in 2034 we’ll all be surprised with QCAD: Parametric Edition

I'd like to think that constraint-based CAD is easier and that it's the inevitability in this space, but agreed that it would be a pile of work.

Personally I would greatly desire parametric features. It's probably the main thing that would get me to purchase the professional version over using the community version.

I'm a long time user of QCAD personally looking for a good alternative for this reason. If QCAD had more parametric capabilities, it would be amazing.

There is a Python package known as "qsketchmetric" that introduces parametric features to QCAD which I am an author of. However, using it does require a besic knowledge of Python. You can find the package on GitHub at this URL:
https://github.com/MadScrewdriver/qsketchmetric

If anyone needs assistance or specific features, I am open to collaborating.

@ mad_screwdriver,
The solution I came up with several years ago is DrawFromCSV, see QCAD Pro: Misc .. Import/Export

It supports all basic drawing entities and their specific attributes, handles layers and layer attributes.
Further it includes 3-point arcs/circles, G-code style arcs, triangles, quadrilaterals, 2 solids, text and supports entities custom properties.
In an upcoming release it supports ellipses.

Parametrization is done outside QCAD in a spreadsheet.
QCAD then draws the model from scratch by a list of instructions in a CSV file.

I agree, less visual to start with but at the moment it exceeds your QCAD-ezdxf-Python-QCAD route.

Regards,
CVH

@CVH

Thanks for the replay! I hope that it is a matter of time when https://github.com/MadScrewdriver/qsketchmetric will support more enteties. [EDIT: It does now supports all of them]
It is not clear for me: On complicated drawing how the parametrization is done without visualization?
Also qsketchmetric route is QCAD-(python using ezdxf pacage) no need for QCAD at the end. QCAD is only used for the initial parametrization of the file after that you can use parametrized file without ever need to use QCAD. Qsketchmetric features rendering evolved from mathematical expressions based on dynamically passed variables from python code. Also it has ability to calculate dynamically position of entities without ever needing to parametrize them. I think that our tools serve a different purpose.

EDIT:
QSketchMetric supports now parametrization of every entity

Regards,
mad_screwdriver

Hi all,

For parametric features check out SOLVESPACE.
SOLVESPACE is a free (GPLv3) parametric 2d/3d CAD tool.
You can find it at "solvespace.com".
It is available for Windows,Mac and Linux.
It comes with a ".exe" file for Windows, an installation file for Mac and for Linux you can build it from source code.
It may be just what you are looking for.

For more comprehensive modelling check out FREECAD.
FREECAD is Your own 3D parametric modeller.
This is a comprehensive 3D modeller and has full parametric features.
You can find it at "www.freecad,org"
It is also available for Windows,Mac and Linux.
However this requires approx. 100MB or more, of disk space, and I would suggest a reasonably powerful laptop or desktop
to run it on.
This might be more what you are looking for.

Hope this helps.

Regards

riverbuoy

@riverbuoy
SOLVESPACE is fantastic! However, currently, it lacks support for dynamically sketching with parameters. It only permits the use of fixed values for parametrization.

andrew wrote: ↑

Wed Jun 29, 2022 5:37 pm

Unfortunately, I can only confirm that there are still no plans for parametric constraints in the foreseeable future for QCAD. While it might be interesting at some point, there are simply too many other priorities. I don't think constraints are very high on the list of what QCAD users want. It hardly ever comes up (once every 12 years ).

I'd love to see dynamic blocks in QCAD - But it has to be implemented in a simple, easy to use way like in AutoCAD (2012 I think).
It's a VERY powerful tool that is pretty easy to use.

@ mad_screwdriver,

I saw your EDITs to the post above: https://www.qcad.org/rsforum/viewtopic. ... 135#p41964

From your qsketchmetric page:

• LWPOLILINE, POLYLINE, SPLINE, ELLIPSE, MTEXT, etc.
  Those entities must be packed into 'INSERT' entity and parameterized as described above.

• INSERT
  Name: must be: 'c'.
  Value: contains the expression describing width and height of the entity split by a `@` sign. In the format: width@height.
  Both width and height are math expressions (see above) where `?` is only allowed for the one of the dimensions.

• A single MTEXT or as 'INSERT' entity

From that I understand that these entities are supported as scaled as a whole only.

QCAD does not have an 'INSERT' entity type as far as I know ...
How are for example polylines already in a document handled or can they only be inserted by python code?
These can have zero to almost an endless number of vertices, a global or segment specific start and end width.
Meaning that none of vertices have a individual specific constraint.

IMHO you can't change the aspect ratio of a polyline with bulges because that would require ellipse arcs to replace arc segments.
Or that of a spline because it is simply another shape.

I don't see how for example polyline nodes would match with other constrained entities by simply scaling.
An inscribed ellipse won't match with the adapted boundary lines.
And I have similar reservations for the other entity types.

Regards,
CVH

By INSERT entity I ment BLOCK. We work and create with the tools we have. It's better to have scalable polylines than no support at all. There are ongoing efforts to improve support for these entities, and I would appreciate any help with the project. It's always better to focus on the strengths of the project rather than its weaknesses.

Regards,
mad_screwdriver