irclog2html for #brlcad on 20060621

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09:57.23 archivist hmm interest in dimensions is building up, time for another hard look at the database format
13:24.30 brlcad dimensions can be done regardless of the database format
13:24.43 brlcad the database format can support the stashing of any key/value data
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13:37.35 brlcad the real "trick" is two-fold
13:38.20 brlcad 1) extracting the dimensions from the geometry (convert to brep and calculate, or sample the implicit directly)
13:38.54 brlcad 2) providing a user interface for specifying what they want dimensioned and how to display those dimensions
13:39.51 archivist dimensions that are set should control the geometry imho
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13:49.57 archivist the end result will a mixture of derived on the 2d and some driving when the items are created
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14:28.48 brlcad i presume you mean dimensions that are effectively tied to the geometry directly such that they become constraints of a sort
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14:31.43 archivist yes
14:32.19 brlcad hmm.. from a modeling perspective, that gets very tricky
14:32.47 brlcad if I have arbitrary geometry, even just a simple primitive with a dimensioned length
14:32.47 archivist i realise that
14:33.28 brlcad there can be numerous transforms that will evaluate to an increase in that dimension, e.g. stretching and scaling might both make the dimension increase
14:34.06 brlcad and for many prims that could be a completely non-linear transform
14:35.01 brlcad unless it just happened to be one of a handful of fairly well-behaved dimensions, like the diameter of a cylinder or a sphere
14:36.03 brlcad which are pretty trivial of course.. throw in CSG operations and arbitrary dimensions across several primitives and you suddenly have a fairly unsolvable constraint
14:36.23 brlcad unless you always scaled uniformly or something wierd.. :)
14:37.40 archivist yup I get some wonderfull drags in solid works or a nasty error message
14:38.24 archivist one then does it properly forcing dimensions to be sensible or fix relatiions between lines
14:38.33 brlcad heh
14:40.36 archivist It generally checks before attempting the stupid, later versions are better in that respect
14:42.16 brlcad does solidworks let you dimension across parts?
14:42.31 brlcad and modify that dimension directly
14:42.45 archivist drawing correct sizes at the start is less fraught
14:43.01 brlcad hmm?
14:43.47 archivist you can relate a new part to existing parts in an assembly yes
14:44.10 archivist known as drawing "in place"
14:44.13 brlcad but then is that just a position constraint?
14:44.57 archivist well a mod of the assembly will stretch the part or give an error
14:45.01 brlcad i'm thinking of a case where you set a dimension on the span of say a car engine, one for width, one for height etc
14:46.14 brlcad if I selected the width and "increased" it.. what would that do if there were no constraints set?
14:47.17 archivist holes would not line up graphics will overlap
14:47.46 brlcad so it wouldn't stretch all the geometry, just some of it
14:48.14 archivist if it was drawn in place then some stretching would tacke place
14:48.47 archivist it all depends wether parts are related or not
14:49.10 archivist relations can be added or deleted
14:49.14 brlcad relations are implicit constraints.. this simplist case is fully unconstrained
14:49.40 brlcad (just conceptualizing the generic case)
14:50.52 archivist unconstrained part grow and the graphics merge (an interference check needed)
14:52.11 brlcad and what about the case where all parts are related in an assembly (again, the case of a simple engine for example)
14:52.37 brlcad would it simply stretch the engine?
14:53.27 archivist if it could yes (as long as the related join distance does not have a constraint)
14:54.25 brlcad right, was presuming there aren't internal constraints that might impose additional constraints like having a hole some distance from an edge
14:55.39 archivist hole from edge may be able to drag the edge
14:57.43 archivist I shall have to do some test cases I suppose so we can see whats happening
17:36.22 CIA-7 BRL-CAD: 03brlcad * 10brlcad/src/tclscripts/mged/pkgIndex.tcl: commit the empty index like all the others if only to be consistent
18:40.41 archivist did a test case draw chassis solid, insert chassis into assembly, draw engine in place, stretch chassis and engine stretches to fit, keeping bolt holes registered
18:41.34 archivist stretch was by editing the dimension in the chassis part
18:57.09 brlcad that's sort of what I'd hope expect since your dealing with a lower dimension with dependent constraints
18:57.25 brlcad how does it behave if you create a new dimension for the entire enginge?
18:57.56 ``Erik vodka would be nice right about now
18:58.21 ``Erik the funk soul brother
19:01.44 archivist attmpting to constrain the bolt distance of the engine is not allowed
19:03.27 archivist breaking the relation to the chassis would then allow it
20:32.58 CIA-7 BRL-CAD: 03brlcad * 10brlcad/NEWS: 7.6.8 window of opportunity was lost due to merge complications on the 7.6 branch, so cancel it outright. revert, poof, gone.
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