[Gmsh] BRL-CAD for Geometry?

[Christophe Geuzaine]

> On 3 Feb 2017, at 21:14, Todd Pierce <toddcpierce at gmail.com> wrote:
> 
> Gorgeous Stuff Christophe,
> 
> I may be a bit confused here, but it may not address the (live) command-line generation of geometry.  I was looking into what McBain was doing with FreeCAD, but it looks like even what you're doing McBain, is scripting.  Correct me if I'm wrong, but this is the same drawback I'm encountering with Gmsh.  Gmsh won't accept piped input either. 
> 
> I'm looking for a package that can display graphics as the commands arrive at its input pipe.  Yes, this is weird, but I'm trying to embed the entire multi-phyics suite of tools, including the generation of geometry, into a *live* pipeline.  This is a natural language processor I am developing, so the user (me) will require interactivity with the whole process.  Do you guys understand what I'm trying to do?  Notice that BRL-CAD does exactly this, in a fashion quite similar to Gnuplot, where the graphical output is displayed as commands arrive at its input pipe,

As scripts can be executed in Gmsh command by command, you can definitely create a pipe to get an interactive system.

Here's a working example where we create a separate interactive command line program (like gnuplot) that simply feeds in scripting commands to Gmsh: https://onelab.info/svn/gmsh/trunk/utils/solvers/c++/interactive.cpp. You can easily create a similar driver that would use a pipe.

Christophe



> though I have no idea if BRL-CAD can really output the right file type for meshing, or even if you experts would advise against BRL-CAD because it's too primitive for other reasons.
> 
> So, McBain, did I miss your point or can FreeCAD be truly interactive from the command line?  (or in this case, its pipe)
> 
> And Christophe, since you're obviously deep into these types of software, do you have any suggestions?
> 
> -Todd . 
> 
> On Fri, Feb 3, 2017 at 6:49 AM, Christophe Geuzaine <cgeuzaine at ulg.ac.be> wrote:
> 
> As a little teaser, just to let you know that I'm coding a direct interface to OpenCASCADE CAD creation right in .geo files. This will in particular support automatic creation of conform interfaces when you fuse solids, in order to handle internal boundaries.
> 
> Here's what the scripts will look like (not everything is in the SVN trunk yet):
> 
> SetFactory("OpenCASCADE");
> 
> Mesh.Algorithm = 6;
> Mesh.CharacteristicLengthMin = 0.4;
> Mesh.CharacteristicLengthMax = 0.4;
> 
> R = 1.4;
> s = .7;
> t = 1.25;
> 
> Block(1) = {-R,-R,-R, R,R,R};
> 
> Sphere(2) = {0,0,0,R*t};
> 
> BooleanIntersection(3) = { Volume{1}; Delete; }{ Volume{2}; Delete; };
> 
> Cylinder(4) = {-2*R,0,0, 2*R,0,0, R*s};
> Cylinder(5) = {0,-2*R,0, 0,2*R,0, R*s};
> Cylinder(6) = {0,0,-2*R, 0,0,2*R, R*s};
> 
> BooleanUnion(7) = { Volume{4}; Delete; }{ Volume{5}; Delete; };
> BooleanUnion(8) = { Volume{6}; Delete; }{ Volume{7}; Delete; };
> BooleanSubtraction(9) = { Volume{3}; Delete; }{ Volume{8}; Delete; };
> 
> 
> <wiki.png><coool.png>
> 
> 
>> On 2 Feb 2017, at 23:28, G. D. McBain <gdmcbain at protonmail.com> wrote:
>> 
>> 
>> 
>> Sent from ProtonMail, Swiss-based encrypted email.
>> 
>> 
>>> -------- Original Message --------
>>> Subject: [Gmsh] BRL-CAD for Geometry?
>>> Local Time: 2 février 2017 4:07 PM
>>> UTC Time: 2 février 2017 05:07
>>> From: toddcpierce at gmail.com
>>> To: gmsh at onelab.info
>>> 
>>> Hi All, 
>>> It's me again, wondering how I should go about integrating a command-line geometry package into OneLab (or some other chain of multi-physics tools).
>>> As I've mentioned before, although there is no shortage of tools to do meshing, finite element analysis or CFD and so forth, there is no simple way to build geometries from the command line. 
>>> 
>>> Has anybody ever used this BRL-CAD/Mged command line CAD package?  It doesn't look bad, but I do have concerns about it exporting to formats that these meshing and physics programs use.
>> 
>> In the past I have used BRL-CAD's mged command-line tool to create geometries for subsequent CFD simulations.  I used BRL-CAD's g-stl command-line tool to export a triangulation of the bounding surface in STL format.  Gmsh can read this in.
>> 
>> More recently though I'm using FreeCAD which can be scripted in Python and so run from the command-line.  Besides STL, this also outputs IGES, STEP, and BRep, which can contain more information that STL.  Gmsh reads all four formats.
>> 
>> OpenSCAD is an excellent accompaniment to FreeCAD too, especially via Solid Python.
>> 
>> Often my workflow looks like FreeCAD -> Gmsh -> FreeFem++ -> (Gmsh or pandas), with the whole thing run from a single SCons build file.  No GUIs, except for preliminary exploratory work.
>> 
>> I haven't looked into OneLab yet.
>> 
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> 
> -- 
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science 
> http://www.montefiore.ulg.ac.be/~geuzaine
> 
> Free software: http://gmsh.info | http://getdp.info | http://onelab.info
> 
> 

-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

Free software: http://gmsh.info | http://getdp.info | http://onelab.info