Hello world. I enjoyed our conversation yesterday in the channel. I was wondering about a few things, and also figure some of the thoughts should be documented if I'm going to seriously consider GSoC 2009 with BRLCAD :-). First, some links. (And for the record, I don't know if this should be counted as an official GSoC application, since I am more interested in getting feedback at this point.)
http://brlcad.org/wiki/A_Survey_of_Implicit_Constraints_in_Primitives http://brlcad.org/wiki/Libpg_:_A_parametrics/constraint_library libpc src: http://brlcad.svn.sourceforge.net/viewvc/brlcad/brlcad/trunk/src/libpc/ http://brlcad.org/wiki/Google_Summer_of_Code/Project_Ideas#Constraints_and_Parametrics http://brlcad.org/wiki/Google_Summer_of_Code/2008#Parametric_Equations_and_Constraint_Support a blank page? http://brlcad.org/wiki/Constraint_Satisfaction previous developer log: http://parametrics.wordpress.com/ Can someone help clarify the following section? """ Implicit : Constraints implicit in the definition of a primitive : Tangency or perpendicularity of Vectors, Equality of scalars etc. Explicit : Constraints explicitly expressed between two or more primitives. One of the intricate parts of the work is the actual integration of libpc with librt. Associated work going on with libpc involves the creation of a Math Virtual Machine for parsing and evaluating (math) expressions which would be used for stating the constraints, along with the grammar. """ I was wondering about the "explicit constraints" in particular. What does this mean, and can anyone give me an example of another CAD software package that implements that, or how it would be used, or something? Also, what about this "Math Virtual Machine", what does this /mean/? So, presumably, users would type up some sort of mathematical expression which would state/specify constraints? When I've used parametric CAD systems before, I never had to do that- or I've never seen those options- but it's entirely possible that it's very important and something that I should know about. Another topic that we were talking about-- """ Boost Graph Library : for graph based representation of the constraints. Since BGL does not have support for Hypergraphs, the author plans to implement hypergraphs independently while adhering to Boost standards ( probable addition to boost itself) Boos Spirit Library : for the parser based generation of constraint objects from expressions. """ It has been many years since I've worked with the boost library. However, recently I have been working in the Automated Design Lab here at the University of Texas at Austin, on projects involving generative grammars and graph grammars for mechanical engineering problems. For instance, some of the recent work is in the automated design and optimization of gear trains; another fellow works on linkage design, and another on product disassembly sequencing. GraphSynth http://graphsynth.com/ Example, re: gears http://heybryan.org/~bbishop/docs/gears/gears.html (and, btw, I'm working on a gear-CAD generator as a visualization frontend to replace the hacked glxgears script; I've been working on it in pythonOCC, though I might switch on over to BRLCAD) There's a few classes there for the representation of graphs. The way that graph grammars work is by search-and-replace, more or less. Each grammar rule has a left-hand side and a right-hand side. The left-hand side represents a subgraph that it should 'match', and the right-hand side is the replacement. So, there's a 'ruleset' for different domains- a ruleset consists of a list of different grammar rules. A ruleset exists for linkages, for product disassembly, gears, electronic filter circuits, etc., and maybe one will be implemented for parametric constraints? The way that this works is that a 'seed graph' (input) is given, and then it's recursion over the list of possible rules that apply to it, and for each one that matches, that's a branch that is taken, and the branches are explored either in a breadth-first manner or depth-first manner, until there's no more manipulations possible to the graph, at which point you have a list of solutions to the original problem. Now, I'm not entirely sure about explicit constraints and weird grammar notations for constraints, so that's partly why I asked that question previously :-) so that I might be able to see whether or not GraphSynth code (as opposed to the boost library) would be appropriate here. GraphSynth-related references- full bibliography (in BibTeX): http://heybryan.org/books/Manufacturing/campbell/bibliography/campbell.bib presentations: http://heybryan.org/~bbishop/docs/repo/presentations/ (older files are better, and I sincerely apologize for the pptx file format- some I've been able to convert to ODP, however) maybe this presentation would be most helpful: http://heybryan.org/~bbishop/docs/repo/presentations/Wed3-KurtogluCampbell-From%20Black-Box%20To%20Component%20Selection.odp ** Relevant diagrams- ** Recognize-Choose-Apply http://www.me.utexas.edu/~adl/graphsynth/images/generationProcess.png ^ the general recognize-choose-apply that is automatically executed for depth-first and breadth-first search methods. Left-hand => right hand translocation http://www.me.utexas.edu/~adl/graphsynth/images/applyProcess.png ^ the above is a diagram of how the left-hand side of a grammar rule is spliced into a host graph, i.e. to avoid dangling arcs or misconnected arcs/edges, and other things like that. designGraph classes are usually serialized into XML http://www.me.utexas.edu/~adl/graphsynth/images/designGraphXML.png seed graph example http://heybryan.org/~bbishop/docs/repo/2008-12-11/2008-12-11_waterlifting.gxml screenshot of that example in GraphSynth http://heybryan.org/~bbishop/docs/repo/2008-12-11/2008-12-11_waterlifting.png.PNG One idea that I suggested to 'madant' over IRC yesterday was the idea of representing constraint problems as a seed graph in GraphSynth by having two types of nodes- those nodes which represent an object in BRLCAD's dot g database, and those nodes which represent the type of constraint (parallel, perpendicular, etc.). So, any two nodes that are connected by a node of label 'parallel_$unique_ID' would be required to be parallel, and then some other labels would specify the xyz coordinates (or something), which means the graph for two perpendicular objects constrained to one two dimensions would be "objectA <-> perpendicular_1 <-> objectB" (in reality, there's more than two dimensions to deal with). The work that would need to be done is a ruleset for manipulating those graphs by recognizing the scenarios of perpendicularity and parallelism, and other types of constraints, and consequently find all possible ways of solving those constraints- which I suspect will probably involve a subset of matrix math rules or vector math rules. And again, the idea would be that GraphSynth would go through the recognize-choose-apply loop and automatically generate all possible solutions to the original constraints/seed graph, and then spit out those solutions to {something} (which I need some clarification on, like I said- maybe a user would select from a command line which option to use to solve the constraints problem when resizing, or something?) How about some user case stories? That would be amazingly helpful. I suspect this code would be implemented and integrated as the backend constraints solution engine, but I'm also open to the idea of gluing it together with shell or command line utilities depending on how exactly it's supposed to work when seamlessly integrated (just to make sure I understand completely). So, if I can get some feedback on those issues, that would be great, and maybe also whether or not anyone would be interested in my working on this for GSoC? I have to admit that I'm a little sketchy on some of the implementation details- like how exactly the constraint expression grammar could work, or how to integrate this into the user interface (or, as I'd prefer, into the shell utilities), but that's something that more seasoned developers can make some comments on. And if there's some green lights, I'll definitely spend some more time doing a formal writeup for GSoC. One quick dislcaimer about GraphSynth- the professor who puts most of his effort into it has not been clear on the licensing in the software distribution on graphsynth.com, but however has expressed an interest in throwing it up as GPL (or possibly LGPL), but I feel this is a minor detail and something that can be fixed. Since this is the first time I've made an appearance on the mailing list, I figure I should say a few words about myself. I am a student in mechanical engineering at the University of Texas at Austin, I'm presently a freshman; my main medium of communication is IRC and email- a few of you (Sean?) might know me from the channel, I was more active a few months ago when I was playing around with BRLCAD with a script I was working on to automatically generate spiral membraneless filters to separate cells from water (it's for another lab I'm employed with). I actually have some screenshots and images related to this- if anyone is interested in how it turned out- http://heybryan.org/bioreactor/membraneless_filtration/2008-11-25_gnuplot.png http://heybryan.org/bioreactor/membraneless_filtration/2008-12-15_brlcad.png http://heybryan.org/bioreactor/membraneless_filtration/2008-12-16_spiral_generator_2.png http://heybryan.org/bioreactor/membraneless_filtration/2008-12-16_spiral_generator_2_other_issue.png http://heybryan.org/bioreactor/membraneless_filtration/2008-12-16_spiral_generator_works.png http://heybryan.org/bioreactor/membraneless_filtration/2009-01-22.png http://heybryan.org/bioreactor/membraneless_filtration/2009-02-01.png one-half the physical object: http://heybryan.org/bioreactor/membraneless_filtration/2009-03-18_spiral.jpg In truth, the spiral flter design generator was not used to make the design that is in that photograph, although I am still working on it (off and on). In particular, I remember also trying out the brlcad pipes command (thanks to Sean, again), and maybe I'll go back to that at some point. Recently elmerfem successfully compiled and began working on my development machine, so there's also the opportunity to explore the fluid dynamics of the delta density of flows through this elegant contraption. (and also the possibility of sharpie microfluidics- of being able to draw similar designs with a sharpie and a paperclip between two sandwiched CDs- which I posted to the diybio mailing list, if anybody is interested in that, or the design possibilities related to that, but this is quickly becoming off-topic.) Anyway, back to the 'about me'. I have been programming for ages, been submitting a few patches to a few different projects, my most favorite (and most simple!) was a patch to KDE for the vertical kicker taskbar in 3.5 so that you don't have to hold down the little arrows to scroll when you have many hundreds of windows open (something you might recognize from the screenshots)- so now the mousewheel properly works and it's much easier to get to everything's that open (other than ALT+TAB). More broadly, I cultivate an interest in mostly anything- more recently it has been in open source hardware and open manufacturing ( http://openmanufacturing.net/ ), which means exploring areas like semiconductor manufacturing, machining, microfluidics, electronic design automation, singularity-related technologies, etc. I have over 15,000 bookmarks, 170+ mailing list subscriptions, many hundreds of forums that I try to keep an eye on, and am generally an intense fellow. Hi. Please don't make me list all past programming projects :-). More stuff on my website for the "about me" aspects- feel free to email me off-list if this isn't detailed enough, so that I don't clog the mailing list with "me me me" :-). After looking at Manuel's application, maybe I've gone a bit overboard here with details? http://sourceforge.net/mailarchive/forum.php?thread_name=200803310541.10578.manuel.montezelo%40gmail.com&forum_name=brlcad-devel Okay. That's all for now. - Bryan (irc nickname: 'kanzure') http://heybryan.org/ 1 512 203 0507 Automated Design Lab University of Texas at Austin http://www.me.utexas.edu/~adl/ http://twitter.com/UTADLab ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. 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