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<p class=MsoPlainText>Echoing others' advice using Einstein: "A clever
person solves a problem. A wise person avoids it." <o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>A thought for "wisdom": if you want to
simplify the shading effect of an even helix, one might consider a helix looks
identical from any angle along a horizontal plane - you might get a 'good enough'
approximation at low sun angles using a simple 2D silhouette of the shape!<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>If you want to go the "accurate" route (now I'm
trying to be clever... oh dear), I was intrigued by the challenge and after playing
with the idea a bit in excel I can point you towards the math required to
generate vertices for a helical shape... I think it's ultimately possible in
eQuest, but it would be very hard. Nothing I'd encourage/advocate in any sense...
just sharing what I found for the curious. I would much sooner seek a “reasonable
approximation.”<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>x(t) = r*cos (B*t)<o:p></o:p></p>
<p class=MsoPlainText>y(t) = r*sin (B*t)<o:p></o:p></p>
<p class=MsoPlainText>z(t) = t<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>where:<o:p></o:p></p>
<p class=MsoPlainText> coil height = period = 2pi/B <-- set B = 2pi/(coil
height)<o:p></o:p></p>
<p class=MsoPlainText> r = radius<o:p></o:p></p>
<p class=MsoPlainText> t = interval for points = angle between points, viewed from
above (expressed in fractions of pi)<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Those three functions along with the variables as
described will return a helix in cartesian (xyz coordinates). You could in
theory generate a full set, then "offset" the original along the
z-axis by the thickness of your actual "coil" to get the other half
of the vertices. Alternating between these sets, you could define a series of 2d
planes which together would look pretty much like a coil spiraling as high as
you'd want it to… But you would undoubtedly save time by defining polygons
for a height equal to a certain even number of periods, then copy/pasting the
result as it would repeat for the resulting height. I would definitely advise
caution/consideration before setting the 't' variable to anything less than
pi/6, lest you end up with magnitudes more polygons beyond reason. <o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>For your sake, I'm starting to hope you don't even read
past the first few lines... haha!<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>~Nick<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>PS: Here’s a screengrab of what I came up with for
illustration:<o:p></o:p></p>
<p class=MsoPlainText> <img width=897 height=630 id="Picture_x0020_1"
src="cid:image001.png@01CC4084.142F0BB0"><o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>NICK CATON, P.E.<o:p></o:p></p>
<p class=MsoPlainText>SENIOR ENGINEER<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Smith & Boucher Engineers<o:p></o:p></p>
<p class=MsoPlainText>25501 west valley parkway, suite 200<o:p></o:p></p>
<p class=MsoPlainText>olathe, ks 66061<o:p></o:p></p>
<p class=MsoPlainText>direct 913.344.0036<o:p></o:p></p>
<p class=MsoPlainText>fax 913.345.0617<o:p></o:p></p>
<p class=MsoPlainText>www.smithboucher.com <o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>-----Original Message-----<br>
From: bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] On Behalf Of Sami, Vikram<br>
Sent: Tuesday, July 12, 2011 10:11 AM<br>
To: Lars O. Grobe; bldg-sim@lists.onebuilding.org<br>
Subject: Re: [Bldg-sim] Energy Modeling for Complex Facade<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>I agree with Lars here. Energy efficiency applies to the
modeling process too.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>You might want to start out with a sensitivity study just
to establish what percentage of the total project energy, cooling & heating
loads are coming from the façade. If its relatively small, then it doesn't make
sense to use a ton of resources modeling it exactly, and you might want to
create an approximate equivalent - either by simplifying the geometry or by scheduling
transmittance.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>If it is actually a large percentage of your building
load, then I would look a little bit more in depth as to how it might be
modeled.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Vikram Sami, LEED AP BD+C<o:p></o:p></p>
<p class=MsoPlainText>Sustainable Design Analyst<o:p></o:p></p>
<p class=MsoPlainText>1315 Peachtree St. NE, Atlanta, GA 30309<o:p></o:p></p>
<p class=MsoPlainText>t: 404-443-7462 f: 404.892.5823 e:
vikram.sami@perkinswill.com www.perkinswill.com<o:p></o:p></p>
<p class=MsoPlainText>Perkins+Will. Ideas + buildings that honor the broader
goals of society<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>-----Original Message-----<o:p></o:p></p>
<p class=MsoPlainText>From: bldg-sim-bounces@lists.onebuilding.org [mailto:bldg-sim-bounces@lists.onebuilding.org]
On Behalf Of Lars O. Grobe<o:p></o:p></p>
<p class=MsoPlainText>Sent: Tuesday, July 12, 2011 5:36 AM<o:p></o:p></p>
<p class=MsoPlainText>To: bldg-sim@lists.onebuilding.org<o:p></o:p></p>
<p class=MsoPlainText>Subject: Re: [Bldg-sim] Energy Modeling for Complex
Facade<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>12.07.2011 11:04 Marcus wrote:<o:p></o:p></p>
<p class=MsoPlainText>> I've had a little experience in complex envelope
geometry, although I've<o:p></o:p></p>
<p class=MsoPlainText>> never used ArchiCAD or Ecodesigner. Generally
speaking though, energy<o:p></o:p></p>
<p class=MsoPlainText>> modeling software can't use curved geometry. Any
curved surface has to<o:p></o:p></p>
<p class=MsoPlainText>> be approximated using planar surfaces. Modeling
software need this<o:p></o:p></p>
<p class=MsoPlainText>> planar geometry in it's internal algorithms,
especially to calculate the<o:p></o:p></p>
<p class=MsoPlainText>> radiative heat transfer and shading.<o:p></o:p></p>
<p class=MsoPlainText>><o:p> </o:p></p>
<p class=MsoPlainText>> The approach I have used, for Energyplus, is to
manually mesh a curved<o:p></o:p></p>
<p class=MsoPlainText>> surface using many smaller triangular surfaces.
There are likely ways to<o:p></o:p></p>
<p class=MsoPlainText>> automate the process if you have very complex and
large geometry.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Hi!<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Meshing geometry may be necessary, but will result to a
complex model<o:p></o:p></p>
<p class=MsoPlainText>with a lot of potential for error. From what I
understand, this may<o:p></o:p></p>
<p class=MsoPlainText>result in a huge number of polygons, as "spiral 3d
shading" sounds a lot<o:p></o:p></p>
<p class=MsoPlainText>like smooth shapes possibly highly specular surfaces
(which is why I was<o:p></o:p></p>
<p class=MsoPlainText>asking for details). Archicad can output meshes (I
remember obj), but it<o:p></o:p></p>
<p class=MsoPlainText>would be important to check mesh quality.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>It would be interesting to assess the need for such a
model here, or<o:p></o:p></p>
<p class=MsoPlainText>whether the performance could be represented by a simple
plane with<o:p></o:p></p>
<p class=MsoPlainText>transmissive properties according to the more complex
shading. If<o:p></o:p></p>
<p class=MsoPlainText>surfaces are diffuse and view is blocked, maybe a flat,<o:p></o:p></p>
<p class=MsoPlainText>diffuse-transmissive material could replace the shading's
complex<o:p></o:p></p>
<p class=MsoPlainText>geometry. If there is direct view through the shading, as
long as the<o:p></o:p></p>
<p class=MsoPlainText>surfaces are not specular, the actual shape should not
matter and a much<o:p></o:p></p>
<p class=MsoPlainText>simplified replacement according to thickness and angles
related to the<o:p></o:p></p>
<p class=MsoPlainText>facade normal would probably be sufficient. If it is a
curvy specular<o:p></o:p></p>
<p class=MsoPlainText>shading, it is going to be difficult!<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>Cheers, Lars.<o:p></o:p></p>
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