7 ms·

Can you explain more? Which things are impossible in blender

timonoko 1y ago
If you try OpenScad-style adding and subtracting volumes, the syntax is pretty horrific. It is impossible to script objects that way. Quote Gemini: However, implementing a full OpenSCAD-like syntax and robust CSG system from scratch in Blender Python is complex due to Blender's mesh-based nature versus OpenSCAD's mathematical description. Blender's boolean operations on complex meshes can sometimes lead to topological errors.
- jacquesm 1y ago
  To be fair though, OpenSCAD works best too if you do this during the generative step and not after the fact. I've used it to remix existing STLs so it definitely does work but you really have to watch the areas where two shapes get close to each other, especially if there is a lot of fine detail.
- timonoko 1y ago
  Did I solve all problems that OpenSCAD might have? Compared to FreeCAD. Me myself think I did: https://youtu.be/eG5lhLYvihQ?si=yA00IYVU4_Zemdxi https://youtu.be/eG5lhLYvihQ?si=yA00IYVU4_Zemdxi
argomo 1y ago
Spiritually, Blender is to FreeCAD what Gimp is to Inkscape or what BMP is to SVG. With Blender you're massaging piles of anonymous polygons so they look right aestheticallY, while with CAD you're composing geometric primitives to make a precise blueprint for a 3D object that just happens to be rendered with polygons. The former is better for art while the latter is better for manufacturing.
- koolala 1y ago
  Any there any open CAD file formats that lay a foundation for describing this kind of 3D data without classic triangles?
  - Klaus23 1y ago
    A .step or .stp file encodes the model as mathematical shapes, rather than approximating it with polygons, but it doesn't save the entire parametric workflow or history, only the final result. As far as I know, there is no widely adopted file format that also saves this information.
  - oever 1y ago
    For architecture, there is Industry Foundation Classes (IFC). IFC is a standard for describing building. FreeCAD supports this natively. There's a tutorial here: https://yorik.uncreated.net/?blog%2F2025%2F002-nativeifc-tutorial https://yorik.uncreated.net/?blog%2F2025%2F002-nativeifc-tut... Blender has and extension for IFC called Bonsai. https://extensions.blender.org/add-ons/bonsai/ https://extensions.blender.org/add-ons/bonsai/
  - gf000 1y ago
    Parent's comparison is pretty great, but it shouldn't be "overdone". It's not really the format that's different/a problem (it's not hard to make a blender object from a CAD design - the same way an SVG can be rendered to PNG, and similarly irreversible in both cases), it's the whole design flow. CAD uses geometry primitives with parameters and exact sizing (e.g. you draw a rectangle of this size, and cut a whole into it this and this offset from one of the corners, and you expand this shape to 3D). As mentioned this can be approximated via geometry nodes, but they are very different in "ideology".
mamonoleechi 1y ago
CAD modeller are good at producing parametric 3d models. You can make use of spreadsheets and constraints to create a piece, that will later super easily be changed. https://en.wikipedia.org/wiki/Constraint_(computer-aided_design) https://en.wikipedia.org/wiki/Constraint_(computer-aided_des...
- diggan 1y ago
  > CAD modeller are good at producing parametric 3d models If that's the only thing they do better than Blender, then it sounds like their days are numbered. Has to be more benefits right? Blender exposes a pretty wide Python API, loading spreadsheets ends up pretty simple, and together with Geometry Nodes, you can even visualize it in a way that makes somewhat sense. Constraints been existing for a long time in Blender too.
  - jijijijij 1y ago
    They are better at it on a fundamental level. It’s a completely different approach for data representation, offering precision and repeatability which is not possible with Blender's data model. Blender may as well replace CAD apps in the hobbyist 3D printing space, but it will never replace them in the industry and professional work. Solid modeling CAD software commonly features more than just creating mathematically precise digital 3D objects, but also planning for CNC machining, FEM analysis, assembly and so on.
    - diggan 1y ago
      > It’s a completely different approach for data representation, offering precision and repeatability which is not possible with Blender's data model. How exactly? And why not? You need useful measurements/units, reproducibility, parameters, constraints, and I guess something more? As Blender can give you those things, it's not impossible in Blender. Want to have 3D objects automatically created based on values from CSVs together with constraints? Blender can already do that today, just as one example. I don't really mind if Blender has a chance of replacing CAD apps or not, more curious about why exactly people find it so fundamentally impossible for Blender to be a useful alternative, and I have yet to hear any convincing arguments.

If you try OpenScad-style adding and subtracting volumes, the syntax is pretty horrific. It is impossible to script objects that way. Quote Gemini: However, implementing a full OpenSCAD-like syntax and robust CSG system from scratch in Blender Python is complex due to Blender's mesh-based nature versus OpenSCAD's mathematical description. Blender's boolean operations on complex meshes can sometimes lead to topological errors.

jacquesm 1y ago
To be fair though, OpenSCAD works best too if you do this during the generative step and not after the fact. I've used it to remix existing STLs so it definitely does work but you really have to watch the areas where two shapes get close to each other, especially if there is a lot of fine detail.
timonoko 1y ago
Did I solve all problems that OpenSCAD might have? Compared to FreeCAD. Me myself think I did: https://youtu.be/eG5lhLYvihQ?si=yA00IYVU4_Zemdxi https://youtu.be/eG5lhLYvihQ?si=yA00IYVU4_Zemdxi

argomo 1y ago

Spiritually, Blender is to FreeCAD what Gimp is to Inkscape or what BMP is to SVG. With Blender you're massaging piles of anonymous polygons so they look right aestheticallY, while with CAD you're composing geometric primitives to make a precise blueprint for a 3D object that just happens to be rendered with polygons. The former is better for art while the latter is better for manufacturing.

koolala 1y ago
Any there any open CAD file formats that lay a foundation for describing this kind of 3D data without classic triangles?
- Klaus23 1y ago
  A .step or .stp file encodes the model as mathematical shapes, rather than approximating it with polygons, but it doesn't save the entire parametric workflow or history, only the final result. As far as I know, there is no widely adopted file format that also saves this information.
- oever 1y ago
  For architecture, there is Industry Foundation Classes (IFC). IFC is a standard for describing building. FreeCAD supports this natively. There's a tutorial here: https://yorik.uncreated.net/?blog%2F2025%2F002-nativeifc-tutorial https://yorik.uncreated.net/?blog%2F2025%2F002-nativeifc-tut... Blender has and extension for IFC called Bonsai. https://extensions.blender.org/add-ons/bonsai/ https://extensions.blender.org/add-ons/bonsai/
- gf000 1y ago
  Parent's comparison is pretty great, but it shouldn't be "overdone". It's not really the format that's different/a problem (it's not hard to make a blender object from a CAD design - the same way an SVG can be rendered to PNG, and similarly irreversible in both cases), it's the whole design flow. CAD uses geometry primitives with parameters and exact sizing (e.g. you draw a rectangle of this size, and cut a whole into it this and this offset from one of the corners, and you expand this shape to 3D). As mentioned this can be approximated via geometry nodes, but they are very different in "ideology".

mamonoleechi 1y ago

CAD modeller are good at producing parametric 3d models. You can make use of spreadsheets and constraints to create a piece, that will later super easily be changed. https://en.wikipedia.org/wiki/Constraint_(computer-aided_design) https://en.wikipedia.org/wiki/Constraint_(computer-aided_des...

diggan 1y ago
> CAD modeller are good at producing parametric 3d models If that's the only thing they do better than Blender, then it sounds like their days are numbered. Has to be more benefits right? Blender exposes a pretty wide Python API, loading spreadsheets ends up pretty simple, and together with Geometry Nodes, you can even visualize it in a way that makes somewhat sense. Constraints been existing for a long time in Blender too.
- jijijijij 1y ago
  They are better at it on a fundamental level. It’s a completely different approach for data representation, offering precision and repeatability which is not possible with Blender's data model. Blender may as well replace CAD apps in the hobbyist 3D printing space, but it will never replace them in the industry and professional work. Solid modeling CAD software commonly features more than just creating mathematically precise digital 3D objects, but also planning for CNC machining, FEM analysis, assembly and so on.
  - diggan 1y ago
    > It’s a completely different approach for data representation, offering precision and repeatability which is not possible with Blender's data model. How exactly? And why not? You need useful measurements/units, reproducibility, parameters, constraints, and I guess something more? As Blender can give you those things, it's not impossible in Blender. Want to have 3D objects automatically created based on values from CSVs together with constraints? Blender can already do that today, just as one example. I don't really mind if Blender has a chance of replacing CAD apps or not, more curious about why exactly people find it so fundamentally impossible for Blender to be a useful alternative, and I have yet to hear any convincing arguments.