Hello Qiang, welcome! > I really like the idea of drawing with simple command. But I read a post on > freeCAD forum comparing the two programs. It says that it is very hard or > impossible to do the following in BRL-CAD: > offset on non trivial geometry, fillets and chamfer on non trivial geometry, > draft angles on non trivial geometry
You’re undoubtedly familiar with a feature based editing approach, as those are feature operations you listed. We will eventually add intrinsic support so they are preserved as parametric operations, but currently they are handled like any other modeling operation. If you want a chamfer, for example, you subtract. Offsets are a trivial surface and/or object move. None of them are impossible but it is true that some of those operations can be a challenge, depending on the geometry involved. For some (non-trivial) shapes, it can actually be easier to perform an offset or chamfer operation in BRL-CAD. For others, it can indeed be difficult. The solid modeling construction methods in BRL-CAD lend themselves more to a different approach in general. Basically, our systems come at the problem from separate ends of a spectrum. We focused a LOT on core solidity concepts — on solid fidelity, ray tracing evaluation performance, correctness, representation flexibility, numerical robustness, etc., and only recently towards adding boundary representation support, parametric features, and usability/GUI. This is a foundation that is heavily centered around a specific domain of computer-aided engineering (CAE) for analysis purposes. That means there is almost certainly a way to create and evaluate any shape you want, however complex, but there is a proficiency learning curve. > Are these all true? If so, what should we do to model all these real life > things that are not composed of simple primitive shapes? With incredibly few exceptions, nearly every complex shape can be decomposed into combinations of more primitive shapes. If you check out our gallery, you’ll see plenty of more complex examples ** that were composed from simple primitive shapes (including complete vehicles with chamfers, fillets, etc). Here’s an example model included in BRL-CAD's installation: https://www.youtube.com/watch?v=xzaKWzntnmc More here: http://brlcad.org/gallery/renderings Cheers! Sean ** Alas, hundreds of the most detailed examples of BRL-CAD models are not available to the public. ------------------------------------------------------------------------------ Monitor Your Dynamic Infrastructure at Any Scale With Datadog! Get real-time metrics from all of your servers, apps and tools in one place. SourceForge users - Click here to start your Free Trial of Datadog now! http://pubads.g.doubleclick.net/gampad/clk?id=241902991&iu=/4140 _______________________________________________ BRL-CAD Users mailing list brlcad-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/brlcad-users
