Real CAD, open source

Sifting through the Reprap forums, blogs and wiki brought some interesting links to CAD items. Because Reprap is open source, Adrian and his team tend to endorse open source and freely available CAD and drawing projects. This year has seen some released that are based on the OpenCascade platform. OpenCascade was started by Matra Datavision as a new platform for their Euclid product, then the project was spun off to open source when Matra sold Euclid to Dassault Systems. It's an attempt to create an open source 3D platform or kernel, similar in concept to Dassault/Spatial's ACIS or Parasolid's X_T. Three applications that utilise it are Dan Heeks' HeeksCAD, FreeCAD and NaroCAD. As with commercial programs that use ACIS and Parasolid, not all of the capacities of OpenCascade are utilised in each of these applications, but they exchange data with neutral file formats as well as proprietary ones. These programs have the capacity to perform some sophisticated functions that up until now have only been seen in commercial apps, like filleting/blending and chamfering and thickening/offsetting of surfaces. After installing NaroCAD, it wouldn't initialise for me, so although it READS like the most powerful, offering splines and revolved surfaces that the other two don't, I can't offer an opinion yet. Of the other two, I've been finding HeeksCAD more useable for modeling than FreeCAD, and more fun. Its GUI and constraints are more integrated and more friendly, whereas FreeCAD has a sort of modular interface, with different tool palettes for 2D drafting, 3D modeling, and working with meshes. Although there are toolbars for some functions, some of them aren't functional yet, and the way they're implemented ignores contextual relationships between functions. FreeCAD might be the more powerful of the two, though, as I've loaded some big model files created in other applications to test them both out, and FreeCAD loads them more quickly and is more responsive with them loaded. FreeCAD handles some mesh/facet formats that HeeksCAD doesn't, and has more sophisticated editing and analysis of mesh objects.

I'll post more about them when I can quantify the differences.