On Monday, March 23, 2009, at 10:19AM, "Bryan Bishop" <[email protected]> wrote:
>I see. I need to think some more about how to represent the difference >between explicit and implicit constraints if something like GraphSynth >were to be used. Implicit constraints seem to be attached to objects, >while explicit constraints seem to be externally imposed- either a >constant, or related to another variable and how that other variable >changes. An MVM does sound useful, and I think it would be even more >appropriate, rather than just having a small data structure for the >expression of these types of constraints that would be converted into >the GraphSynth GXML format directly. Actually, since it's still raw >data it can conceptually be converted, but I don't know if I want to >write a compiler grammar for doing that :-) and an MVM might be more >useful. So that's something to take into account. There's not really any need to distinguish between an implicit and explicit constraint. The same solving system works for either as they're just series of expressions. Moreover, the implicit ones are going to be hard-wired into the source code for the primitives themselves as an intrinsic property so there isn't going to be a way for users to change those expressions. The primitives just declare their set of (implicit) requirements and will validate their internal consistency when requested (some sort of validate() routine and/or during ray-trace prep()). >Yes, I've seen something like that before, and actually I was >wondering- at the time when I saw a conflict of constraints in a >commercial CAD environment- why they didn't just give me a list of >possible solutions or a list of possible things that I did that >foobar'd the model, which seems like something BRLCAD definitely wants >to implement if it gets a constraints solver (or even constraints >representation as a first step?). You've not seen possible solutions probably because their are infinite numbers of solutions. You can fully constrain any object's position, for example, by adding a constraint that their position is equal to some given absolute xyz coordinate. >LGPL? Okay. I'll look into it. It being LGPL doesn't mean we would use it or even want to use it, but not having license means it's not even something to consider. From the other discussion, it sounds like something that is a little more domain-aware would be more beneficial regardless. >Gaah, I still have to get around to doing this. :-) Thanks for the hints. Noticed that it was working from a different network a couple days ago which could mean that afraid.org may have simply gotten themselves on one of the master blacklists. Given its purpose of providing dynamic DNS, I wouldn't be surprised in the least if someone uses/used the service for some abusive purpose and got it blacklisted. >Ah, well, I was reading the BRLCAD wiki and there was a plea for >diagrams when proposals are typed up, so those are some diagrams of >the backend system of GraphSynth. For instance, a few of those were >explaining how a subgraph is found and replaced such that no dangling >arcs or edges are left over, among other things. Now, if GraphSynth >was to be implemented- which it seems increasingly like it shouldn't- >for BRLCAD, MVM or some data structure would be passed over, it would >be converted into a graph, there'd be a set of rules >(search-and-replace rules, essentially) that find constraints and then >give a possible solution to that subgraph of the larger graph (the >entire problem); at the end you'd get back a list set of graphs that >would represent solutions, possibly with numerical values, of the >solutions to the constraints problem. Diagrams aren't necessary, just very helpful if they are done well. :-) >Yep, should I bug Dawn about this? Absolutely. :) >Hrm. Yes, I remember there being something about a web-based solid >geometry model repository? > >http://brlcad.org/wiki/Google_Summer_of_Code/Project_Ideas#Web-based_solid_geometry_model_repository > >I have been wanting to do something like this for a while now, *but* >I've been eyeing doing it with parametrically constrained models, so I >don't know how I feel about heavy integration with BRLCAD shell >utilities. Any thoughts on this? Lots of thoughts on this one, and it seems to be exceptionally popular. It was the most popular submission last year, yet not selected (there were several "good" proposals, but none outstanding and none that integrated well. This is probably better discussed as a separate thread. Perhaps share what you think is meant by heavy integration and what the concerns are. Cheers! Sean ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ BRL-CAD Developer mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/brlcad-devel
