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It's a very nice 3d primitives collection, but I don't see how it is CAD (at least in context of mechanical engineering). - First of all, as a mechanical engin

by sgdread 12y ago

It's a very nice 3d primitives collection, but I don't see how it is CAD (at least in context of mechanical engineering). - First of all, as a mechanical engineer, you're not dealing with surfaces, you're dealing with 3D objects, created using sets of operations: extrusion, revolution, sweep, etc. (ideally you want to reproduce the manufacture process of a part; in some systems then you can export these operations into series of commands for CNC machine). - Secondary, if the output is not CNC machine, it's usually paper. Then the end result of CAD 3D modelling is a series of sections, projections, tools to annotate dimenstions, put tolerances, etc.

MadManE 12y ago
I agree. This is awesome, and an impressive project, but I just don't see the usefulness -- yet. Are these able to be output in a STEP or IGES format? Compatibility with the current standards is a major step. (I am so sorry for the pun)
AndrewKemendo 12y ago
Correct me if I am wrong, but our work with 3D CAD models in revit, Max and autocad all point to surfaces/meshes being created when 3D functions (extrusion etc...) are applied. When we look at the file hierarchy within an FBX for example we see surfaces/meshes as the core geometry regardless of how they were built. Are you saying there is a functional difference between a vertex/spline/NURBS square that has been extruded and a similar block built as a native 3D object? AFAIK the latter just basically "automates" the extrusion process from the outset instead of having a function or second extrusion step.
- kanzure 12y ago
  Note that even if Solidworks or Autocad has a parametric nurbs-based representation of the model, that they still might be storing a bag of triangles as well. I know they definitely store screenshots in the file for quick file icon rendering....
  - sgdread 12y ago
    I just wanted to point that ability to display surfaces is not CAD. CAD gives you tools you need to do your job efficiently in specific context.
- sgdread 12y ago
  There're different point of views: - If you're 3D modeller, then yes, you're operate in terms of splines, surfaces, NURBS curves, etc. 3D model is your product. - If you're mechanical engineer (and CAD usually appear in engineering context), then in most cases 3D model is just a tool to produce something useful for manufacturing. Engineer models manufacturing process by applying specific primitive operations in specific order(order is important) which will emulate available manufacturing operations (like sweeping, drilling). In other words, when I need to add hole in a part, I don't create surface (or bunch of these - in case if hole intersects other surfaces), I just add extrusion operation; an operation tree will log info "extrusion with diameter 6 at this coordinates from base A and B", not "surface a,b and c". CAD will build all necessary surfaces for me as well as will have all necessary parameter for CNC machine. In 99%* you don't interact directly with surfaces/meshes. At least that's what you do if you work with Autodesk Mechanical Desktop/Autodesk Inventor/SolidWorks/CATIA/Unigraphics. * 1% are rare cases when you have to deliver something really complex like auto body parts (though making those is a whole new story).
  - bhouston 12y ago
    Funny thing, most commercial CAD tools (AutoCAD, Revit, Inventor, CATIA, SolidWorks) are built on a single C++ library from Seimens called Parasolid.
    - delhanty 12y ago
      Ex Parasolid (1989-1995), D-Cubed (1995-2000), and SolidWorks (2001-2002) dev here. Many are built on Parasolid, but many are not. Of your list only SolidWorks is built on Parasolid. Siemens own products (NX, SolidEdge) are built on Parasolid. CATIA uses its own CATIA kernel. Dassault would like to move SolidWorks to the CATIA kernel, but they will encounter user resistance. Autodesk has its own kernel ShapeManager ( http://en.wikipedia.org/wiki/ShapeManager http://en.wikipedia.org/wiki/ShapeManager ) that it uses in Inventor and probably AutoCAD and Revit. ShapeManager was forked from Acis. There was a court case over the fork. Before the fork Autodesk used to use Acis. Dassault owns Acis ( http://en.wikipedia.org/wiki/ACIS http://en.wikipedia.org/wiki/ACIS ) which is also widely used, especially amongst the smaller players. SpaceClaim uses Acis. IIRC ProEngineer has its own kernel.

by sgdread 12y ago

MadManE 12y ago

I agree. This is awesome, and an impressive project, but I just don't see the usefulness -- yet. Are these able to be output in a STEP or IGES format? Compatibility with the current standards is a major step. (I am so sorry for the pun)

AndrewKemendo 12y ago

Correct me if I am wrong, but our work with 3D CAD models in revit, Max and autocad all point to surfaces/meshes being created when 3D functions (extrusion etc...) are applied. When we look at the file hierarchy within an FBX for example we see surfaces/meshes as the core geometry regardless of how they were built. Are you saying there is a functional difference between a vertex/spline/NURBS square that has been extruded and a similar block built as a native 3D object? AFAIK the latter just basically "automates" the extrusion process from the outset instead of having a function or second extrusion step.

kanzure 12y ago
Note that even if Solidworks or Autocad has a parametric nurbs-based representation of the model, that they still might be storing a bag of triangles as well. I know they definitely store screenshots in the file for quick file icon rendering....
- sgdread 12y ago
  I just wanted to point that ability to display surfaces is not CAD. CAD gives you tools you need to do your job efficiently in specific context.
sgdread 12y ago
There're different point of views: - If you're 3D modeller, then yes, you're operate in terms of splines, surfaces, NURBS curves, etc. 3D model is your product. - If you're mechanical engineer (and CAD usually appear in engineering context), then in most cases 3D model is just a tool to produce something useful for manufacturing. Engineer models manufacturing process by applying specific primitive operations in specific order(order is important) which will emulate available manufacturing operations (like sweeping, drilling). In other words, when I need to add hole in a part, I don't create surface (or bunch of these - in case if hole intersects other surfaces), I just add extrusion operation; an operation tree will log info "extrusion with diameter 6 at this coordinates from base A and B", not "surface a,b and c". CAD will build all necessary surfaces for me as well as will have all necessary parameter for CNC machine. In 99%* you don't interact directly with surfaces/meshes. At least that's what you do if you work with Autodesk Mechanical Desktop/Autodesk Inventor/SolidWorks/CATIA/Unigraphics. * 1% are rare cases when you have to deliver something really complex like auto body parts (though making those is a whole new story).
- bhouston 12y ago
  Funny thing, most commercial CAD tools (AutoCAD, Revit, Inventor, CATIA, SolidWorks) are built on a single C++ library from Seimens called Parasolid.
  - delhanty 12y ago
    Ex Parasolid (1989-1995), D-Cubed (1995-2000), and SolidWorks (2001-2002) dev here. Many are built on Parasolid, but many are not. Of your list only SolidWorks is built on Parasolid. Siemens own products (NX, SolidEdge) are built on Parasolid. CATIA uses its own CATIA kernel. Dassault would like to move SolidWorks to the CATIA kernel, but they will encounter user resistance. Autodesk has its own kernel ShapeManager ( http://en.wikipedia.org/wiki/ShapeManager http://en.wikipedia.org/wiki/ShapeManager ) that it uses in Inventor and probably AutoCAD and Revit. ShapeManager was forked from Acis. There was a court case over the fork. Before the fork Autodesk used to use Acis. Dassault owns Acis ( http://en.wikipedia.org/wiki/ACIS http://en.wikipedia.org/wiki/ACIS ) which is also widely used, especially amongst the smaller players. SpaceClaim uses Acis. IIRC ProEngineer has its own kernel.