That $#$#%$ sweep*2 thing

Well friends,

This is my second ever attempt in GH (code is clumsy and stupid and clumsy) > destined (in theory) to be a chaotic truss mess - it's about an air terminal canopy. OK, I should follow Plan A: do that in Gen Comp since there's an awful lot of "components" available (the whole Microstation repertoire, that is - not to mention any solid operation imaginable) ... but GC is so INCREDIBLY slow that makes me cry.

Plan B: GH then...

...but the most basic component (tested the VB thing as well) for that type of stuff, ie the sweep *2, it doesn't work without providing any explanation.

The standard Sweep*2

Play with various "general type" values in the input section (use Saved Views) and observe that (a) the Sweep works selectively when the whole combo is rotated - by that I mean that it works with some angles and doesn't with some others (b) doesn't work at all for canopy divisions greater that 3.

The VB thing

This thing works with divisions and general canopy rotation ... but it doesn't make a complete surface.

Additionally within the same set of points (0,1,...n) the Curve and Interpolate components make (periodic in this case) curves with "different" start (not "aligned" so to speak > see symmetry planes inside the definition). OK, that's not that difficult to explain...but...this is sufficient enough for the Sweep*2 thing to quit the game - even with 3 canopy divisions.

Moral: elementary my dear Watson : Plan A.

He He

Any ideas welcome.

Best, Peter

Attachments:

TERMINAL-CANOPY23A.3dm, 1005 KB

Replies to This Discussion

Permalink Reply by peter fotiadis on December 18, 2011 at 9:52am

Oops forgot the gh

Attachments:

TERMINAL-CANOPY23A.gh, 109 KB

Permalink Reply by peter fotiadis on December 18, 2011 at 11:26am

Hmm...

with regard that not closed sweep (VB case) :

the reason is args.m_bClosed = False instead of True, but:

(a) when set to True > no VB sweep at all,

(b) when correcting the syntax ( i.e. args.m_blnClosed = True) the VB turns red.

Permalink Reply by peter fotiadis on December 18, 2011 at 11:50am

Here's some random combos (general rotation + N of divisions) where the OE Sweep*2 works .. or doesn't:

Permalink Reply by Yoann Mescam (Systemiq) on December 18, 2011 at 2:03pm

Based on this + some additional code.

Does it work ?

Attachments:

TERMINALCANOPY23A_sweep2fix.gh, 115 KB

Permalink Reply by peter fotiadis on December 19, 2011 at 10:29am

Thanks for looking into this (I own you one: if you like fast bikes and a trip to Greece occurs just mail me).

The trick appears working...although this "fool that %##$$% sweep2" approach by providing a N+1 nurbs section profile leads us to the 1M question: why the most useful component of them all (at least for AEC purposes) is so badly engineered? (loft falls into that category as well in quite a few cases).

Q: This surface is closed non-periodic or I got it wrong?

Anyway I believed that only Microstation has tools that work...when they work (he he).

Plan B.1 then (until Plan A, that is) > excuse my ignorance but ... by what GH means can one rebuild a nurbs surface ? (say with the way that Rhino does business - for instance making "uniform" UV distribution etc etc etc). I searched the components available and found no such thing.

kinda like this: (bottom the baked thing, top the simplified)

Reason for asking is obvious: if this "guide" canopy is destined to serve as a template for the usual truss on nurbs motive (actually a truss using 2 nurbs as boundaries)...well you got the puzzle I believe. On the other hand and since Birdair delivered that stunning double insulated membrane material ... neat engineering in this case means tensile membranes (which make the whole definition a bit obsolete, he he).

Best, Peter

Permalink Reply by Yoann Mescam (Systemiq) on December 19, 2011 at 2:09pm

The surface is not closed nor periodic, although the hacked edges are under tolerance distance.

To get a real closed surface you can:

Or bake and join edges in rhino,

or just use GH as preview then bake and sweep rails and profiles when you are happy (well the VB should produce the same result as Rhino's sweep2, but I cant manage to find the bug in it).

I dont quite know how to deal with periodicity (except using rhino sweep).

About rebuilding : http://www.grasshopper3d.com/xn/detail/2985220:Comment:470628

Permalink Reply by peter fotiadis on December 20, 2011 at 2:31pm

Thanks for the enlightenment

However I have bad, bad and bad news:

1. The purpose of this is to design some terminals for a company that wants a "brand" identity (kinda like the BP gas stations - only in a "bigger" scale, he he). Divisions are proposed to suit variable area schedules (small airport with 3 divisions bigger wow stuff with more). My initial intension was to design this via insulated tensile membranes (THE engineering purity) bit client thinks that these are only suitable for some gypsy campus.

2. Goal is to outline a collection of "boundary" surfaces (so far the definition deals only with the exterior skin and an indicative WIP "base") that could define "in-between" them space trusses. See a primitive "generic" outside boundary in the Rhino file (second not shown). Of course ideally this type of forms is actually T-Spline territory, but never mind.

Back to GH thing:

3. See results with C# Surf rebuild and odd results with closed stuff as well.

4. It's obvious that mess relaxation (Geo Gym stuff) methods are required here - working solely with nurbs is a clear dead end (unless applying "weaving" in dense U/V areas) .

Stupid questions section:

(a) how we can trim surfaces in GH? - help in components...er...hmm...is this help?

(b) by what means can we fillet, variable fillet and/or blend surfaces in GH? Of course given an infinitive amount of time one could do that by defining a myriad of suitable curves - but this is CAT not CAD (T=torture).

Best, Peter (one step before Plan A, no actually there's no Plan A since Microstation/Gen Comp can't blend/fillet correctly a thing (or two), he he)

Attachments:

TERMINAL-CANOPY23B.gh, 227 KB
TERMINAL-CANOPY23B.3dm, 746 KB

Permalink Reply by peter fotiadis on December 23, 2011 at 11:34am

I've changed approach (not shown yet : i.e the suspended portions of the canopy should be made by some kind of "dome" structure, more on that soon).

In the mean time, and just for the record, I think that only a periodic thing (I've made a stupid VB to do that) could serve as a meaningful donor for U/V "dome" structure (i.e. U/V aligned properly with regard the symmetry axis around).

Redirect output into your code and compare U/V especially in u/vDeg = 1 situations.

And why all this may you ask? Er...because the sweep2 is faulty/incomplete that's why.

The rather complex final LBS solution in a while.

Best, Peter

Attachments:

TERMINAL-CANOPY23C.gh, 268 KB

Permalink Reply by Yoann Mescam (Systemiq) on December 30, 2011 at 11:23am

Back after a few days away from computer.

Mmmh I am a bit lost in your rather complex definition, but I noticed you missed something for the rebuild thing:

Now with the expression -S, the surface is closed, but does it fix the problem ?

Permalink Reply by peter fotiadis on December 30, 2011 at 12:50pm

No, it doesn't because a closed non-periodic surf could be prone to the known kink (blame that #$# not working sweep*2 and your N+1 profile added etc etc etc). This kink makes things uncontrollable if a rebuild is attempted (try it with d=1 > odd polysurface ).

So the solution is to make that damn thing periodic.

But anyway this is only the generic outline of the whole thing, since nobody actually does that type of symmetric stuff without a modular concept/thinking (i.e. you design the modulus - and the modulus of the modulus - and when ready you apply the suitable rotations).

I'll be back with version D (a far more complex thing, ideally suited for the well known movie "Lost in translation").

But ... and there's always a but in CAD... GH is not actually masterminded in order to handle complex structured definitions for real-life AEC Projects of that type (not to mention the known cluster "glitch"). I think that the only way to use GH for that matter is to quit meshing with components, wires et all and start writing VB code > a fact that brings us towards Microstation and Generative Components mentality (meaning that the more things change the more stay the same, he he).

All the best for NY, peter

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