t defined from the discussion of radiation exchange between urban surfaces and the sky in urban heat island research (See Oke's literature list below). It will be affected by the proportion of sky visible from a given calculation point on a surface (vertical or horizontal) as a result of the obstruction of urban geometry, but it is not entirely associated with the solid angle subtended by the visible sky patch/patches.
So, I think using "geometry way" to approximate Sky View Factor is not correct. Sky View Factor calculation shall be based on the first principle defining the concept: radiation exchange between urban surface and sky hemisphere:
(image extracted from Johnson, G. T., & Watson, 1984)
Therefore, I always refer to the following "theoretical" Sky View Factors calculated at the centre of an infinitely long street canyon with different Height-to-width ratios in Oke's original paper (1981) as the ultimate benchmark to validate different methods to calculate SVF:
So, I agree with Compagnon (2004) on the method he used to calculate SVF: a simple radiation (or illuminance) simulation using a uniform sky.
The following images are the results of the workflow I built in the procedural modeling software Houdini (using its python library) according to this principle by calling Radiance to do the simulation and calculation, and the SVF values calculated for different canyon H/W ratios (shown at the bottom of each image) are very close to the values shown in Oke's paper.
H/W=0.25, SVF=0.895
H/W=1, SVF=0.447
H/W=2, SVF=0.246
It seems that the Sky View Factor calculated from the viewAnalysis component in Ladybug is not aligned with Oke's result for a given H/W ration: (GH file attached)
According to the definition shown in this component, I assume the value calculated is the percentage of visible sky which is a geometric calculation (shooting evenly distributed rays from sensor point to the sky and calculate the ratio of rays not blocked by urban geometry?), i.e solid angle subtended by visible sky patches, and it is not aligned with the original radiation exchange definition of Sky View Factor.
I'd suggest to call this geometrically calculated ratio of visible sky "Sky Exposure Factor" which is "true" to its definition and way of calculation (see the paper on Sky Exposure Factor below) so as to avoid confusion with "The Sky View Factor based on radiation exchange" as discussed in urban climate literature.
Appreciate your comments and advice!
References:
SVF: definition based on first principle
Oke, T. R. (1981). Canyon geometry and the nocturnal urban heat island: comparison of scale model and field observations. Journal of Climatology, 1(3), 237-254.
Oke, T. R. (1987). Boundary layer climates (2nd ed.). London ; New York: Methuen.
Johnson, G. T., & Watson, I. D. (1984). The Determination of View-Factors in Urban Canyons. Journal of American Meteorological Society, 23, 329-335.
Watson, I. D., & Johnson, G. T. (1987). Graphical estimation of sky view-factors in urban environments. INTERNATIONAL JOURNAL OF CLIMATOLOGY, 7(2), 193-197. doi: 10.1002/joc.3370070210
Papers on SVF calculation:
Brown, M. J., Grimmond, S., & Ratti, C. (2001). Comparison of Methodologies for Computing Sky View Factor in Urban Environments. Los Alamos, New Mexico, USA: Los Alamos National Laboratory.
SVF calculation based on first principle:
Compagnon, R. (2004). Solar and daylight availability in the urban fabric. Energy and Buildings, 36(4), 321-328.
paper on Sky Exposure Factor:
Zhang, J., Heng, C. K., Malone-Lee, L. C., Hii, D. J. C., Janssen, P., Leung, K. S., & Tan, B. K. (2012). Evaluating environmental implications of density: A comparative case study on the relationship between density, urban block typology and sky exposure. Automation in Construction, 22, 90-101. doi: 10.1016/j.autcon.2011.06.011
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occur more than once in the same list, and different elements with identical values can occur more than once. Also, a list may contain lack of elements, referred to as "nulls".
Sets. Strictly speaking a Set is a mathematical construct which adheres to a strict collection of rules and limitations. Basically, a Set is the same as a List, with the exception that it cannot contain the same element more than once, or indeed two or more different elements with the same values. You see, in mathematics there is no difference between a value and an instance of that value, they are the same thing. In programming however it is possible to store the number 7 in more than one spot in the RAM. Grasshopper does not enforce this rule very strongly though, you can use a lot of Set components on lists that have multiple occurrences of the same value. The big difference between Lists and Sets in Grasshopper is that Sets are only defined for simple data types that have trivial equality comparisons. Basically: booleans, integers, numbers, complex numbers, strings, points, vectors, colours and intervals. Lists can contain all kinds of data.
Strings. Strings are text. There's nothing more to it. I don't know why early programmers chose to call them strings, but I suppose it's a better description of the memory representation of them. Strings are essentially sequences of individual characters.
Trees. Trees are the way all data is stored in Grasshopper. Even when you only have a single item, it will still be stored in a tree. A tree is a sorted collection of lists, where each list is identified by a path. A specific path can only occur once in a tree, when you merge two trees together, lists with identical paths are appended to each other. Trees are an attempt to losslessly represent not just the data itself, but also the history of that data. Imagine you have 4 curves {A,B,C,D} and you divide each into 3 points {X,Y,Z}. Then, for each of those points you create a new line segment {X',Y',Z'} and then divide each of those line segments again into 5 points each {K,L,M,N,O}. The way data is stored in trees, it should be possible to figure out whether a point M belongs to X' or to Z', and whether that X' or Z' came from A, B, C or D. This is why paths are often quite long after a while, because they encode a lot of history.
Paths. A Path is nothing more than a list of integers. It's denoted using curly brackets and semi-colons: {A;B;...;Z}. A Path should never be empty {} or have negative integers {0;-1}, but it is certainly possible to create a path like this and it probably won't even crash Grasshopper. Paths are 'grown' by components that (potentially) create more than one output value for a single input value. For example Divide Curve. It creates N points for every single input curve. In cases like this a new integer is appended to the end of the path.
In the next release the Path logic in Grasshopper is somewhat different. I fixed a number of obscure bugs (hopefully without introducing new fresh bugs) and special cased certain operations to somewhat reduce the speed at which paths grow. This may well break files that rely on a specific tree layout, but I hope the temporary sacrifice will be worth the long-term benefits.
--
David Rutten
david@mcneel.com
Poprad, Slovakia…
http://www.pilkington.com/) dominates the planar market. Charges "around" 1K Euros per m2 for a "plain" system. Personally in bespoke projects I design my own stuff but due to economies of scale ... they cost a bit more (but they look far more sexier, he he) . On the other hand only in a bespoke project I could dare to suggest such a solution (for a large scale building we are talking lots and lots of dollars).
3. Several scales below (aesthetics) you can find static alu systems (either structural or semi-structural):
Or hinged systems (either structural or semi-structural) capable to adapt in contemporary double curvature facades/roofs/envelopes/cats/dogs etc etc ... pioneered worldwide many years ago by my best friend Stefanos Tampakakis (everybody in UAE knows that genius man: http://www.alustet.gr/company.html):
4. With the exception of some paranoid things that Guru Stefanos does for Zaha these days we are talking about planar "facets" (obviously a triangle is such a planar facet). The current trend is: the more edges the better (humans excel in vanity matters). But achieving planarity in, say, quads (like yours) it adds another "restriction" on what you are doing. Until recently Evolute Tools Pro was the only answer. But right now ... well let's say that in short time you'll be greatly surprised by some WOW things in this Noble Forum, he he.
5. MERO (and obviously custom systems) can adapt (at almost no extra charge) in anything imaginable. But in a bespoke building ... well.. you know ultra rich people: they don't want MERO anymore since "everybody" does MERO solutions. Vanity, what else?
6. Smart Glass would become a must in the years to come: Eco-Architecture MUST dominate everything you do. On the other hand spending millions to do some extra WOW stuff (Vanity) ... it doesn't look to me very Eco-Friendly/Whatever ... but let's pretend so, he he.
7. I'm Architect but a bit different from the norm: for instance I smoke cigars (highly politically incorrect stuff) I always talk openly (ditto) and I ride lethal bikes (ditto).
may the Force (as always the Dark Option) be with you: go out there and kill them all.
best, Peter
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radiance parameters to get rid of blotching. To add another level of complexity to my problem, I am running simulations with a translucent material with the following properties: void trans testTrans
0
0
7 0.478 0.478 0.478 0.000 0.010 0.178 0.635
I have had no issues with the renderings when I use clear glazing, as seen on this image:
However the blotching-issue becomes very noticeable when I introduce translucent glazing into the scene:
For the two above cases I used the following parameters:
_av_ is set to 0
xScale is set to 2
_ab_ is set to 6
_dc_ is set to 0.5
_aa_ is set to 0.2
_ad_ is set to 2048
_st_ is set to 0.5
yScale is set to 2
_ps_ is set to 4
_ar_ is set to 64
_as_ is set to 2048
_ds_ is set to 0.25
_pt_ is set to 0.1
_dr_ is set to 1
_pj_ is set to 0.9
_dp_ is set to 256
_dt_ is set to 0.25
_lr_ is set to 6
_dj_ is set to 0.5
_lw_ is set to 0.01
I ran another test with increased Radiance parameters and got the following output:
with the following parameters:
_av_ is set to 0
xScale is set to 6
_ab_ is set to 6
_dc_ is set to 0.75
_aa_ is set to 0.1
_ad_ is set to 4096
_st_ is set to 0.15
yScale is set to 6
_ps_ is set to 2
_ar_ is set to 128
_as_ is set to 4096
_ds_ is set to 0.05
_pt_ is set to 0.05
_dr_ is set to 3
_pj_ is set to 0.9
_dp_ is set to 512
_dt_ is set to 0.15
_lr_ is set to 8
_dj_ is set to 0.7
_lw_ is set to 0.005
Although the second blotching case is much better than the first, it is still very bad for hours when the sun is lower in the sky. The above images are rendered for a clear sky at 18:00 in Germany in a West-facing room.
Sorry for the long post! Can someone help? Kind regards, Örn
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into one file is a good poor-man's way to look at both at once. Good thought.
I really like your approach to pushing the four separate colours of line into separate branches of a single tree and then sorting it out at the end with a tree of materials. This is definitely the 'Grasshopper way'! Nice. I kept them separate because visualizing one at a time helped debugging and baking.
You are right about the three extra weave bumps. This was deliberate, but technically wrong. They are mostly invisible under the overpass thread.
I should explain the early stages.
I was initially not thinking at all about the box-morph thing, but was aiming to create a simple plane. This was the cause of later problems, but more of that below.
The initial approach is to make a 6x6 grid of points and then to shift these points up and down in the z axis to define the different levels in the weave. If you look at the Z-vector inputs to the weave, you will see that the values are actually an array of 36 values, between -5 and +5. I should have 'extracted parameter' to make this more clear. There are six possible levels: two for each basic weave and two more for the overpass threads.
The lines themselves run between pairs of points. The magic here is also rather disguised. In the 'lines' group, the Index input to the List Item sector is actually an array of 26 indexes. Again, I should have 'extracted parameter' here.
These 26 lines are orthogonal to the axes, but I actually need four sets of threads all at angle to one another. 0.197396 is arctan 1/5, in radians.
The resulting pattern has a ragged edge, but working in a plane, this is fine; the pattern tiles properly. I used the pattern to sweep out an ellipse and it printed nicely. I attach a photo of a Shapeways print.
I then started to have ambitions to make a proper surface, using a Box Morph to distribute the tiles. At this point the fact that my basic tile had ragged edges started to matter. I wasted a lot of time trying to make the same tiling within a square boundary and then it dawned on me that if I simply doubled up the pattern to give a 2x2 shape and then clipped the middle out of it with a square boundary, that would be the pattern I needed. I failed to spot the "Trim with Brep", which is where this thread began.
The trimmed pattern now reaches its bounding box faces correctly and can be used for the Box Morph.
As to the stool, yes, I did that myself. It is the same weaving, but it had to be made by threading each string in from the ends, round the bar and back into the pattern again. Because the threads go in four directions, you cannot use a traditional weaving technique - you need a needle to thread the string. There are only 10 pieces of string. Tedious stuff! I was stuck in Bruxelles for a year in 1985, working for SHAPE, and needed some mental relaxation in the evenings to keep my sanity!
Best wishes,
Bob
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Added by Bob Mackay at 12:20pm on November 22, 2015
he "return" is comment out as shown below?
After restarting Rhino and Grasshopper, I opened the outdoors_airflow demo file, and the first step of creating the case file is ok:
Then the blockMesh component gives the following error: seems I have to manually start OF first..
so, as the error message suggested, I open OF by Start_OF.bat:
Then come back to the blockMesh component, now it can be executed while the OF command line window is also openning:
... and the blockMesh finished successfully:
... so I proceeded to run snappyHexMesh, checkMesh and update fvScheme:
... up to the simpleFoam component, I got the error again:
The warning message is:
1. Solution exception: --> OpenFOAM command Failed!#0 Foam::error::printStack(Foam::Ostream&) in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so" #1 Foam::sigFpe::sigHandler(int) in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so" #2 ? in "/lib64/libc.so.6" #3 double Foam::sumProd<double>(Foam::UList<double> const&, Foam::UList<double> const&) in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so" #4 Foam::PCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so" #5 Foam::GAMGSolver::solveCoarsestLevel(Foam::Field<double>&, Foam::Field<double> const&) const in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so" #6 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMatrix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so" #7 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libOpenFOAM.so" #8 Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/lib/libfiniteVolume.so" #9 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/bin/simpleFoam" #10 Foam::fvMatrix<double>::solve() in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/bin/simpleFoam" #11 ? in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/bin/simpleFoam" #12 __libc_start_main in "/lib64/libc.so.6" #13 ? in "/opt/OpenFOAM/OpenFOAM-v1606+/platforms/linux64GccDPInt32Opt/bin/simpleFoam"
... and the command lines in the readMe! output are pretty long and it is saved in the text file attached here.
So, my questions are:
1. why I have to manually start OF first before I can use the blockMesh component? Should butterfly automatically start OF?
2. what might be the cause of the unsuccessful run of simpleFoam in the end?
Hope you can kindly advise! Thank you!
- Ji
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e:
Modulo 1Il workshop è finalizzato a fornire ai partecipanti i fondamenti della modellazione parametrica e generativa attraverso Grasshopper, plug-in di programmazione visuale per Rhinoceros 3D (uno dei più diffusi modellatori NURBS per l‘architettura e il design). Il workshop mira a gestire e sviluppare il rapporto tra informazione e geometria lavorando sui sistemi di involucro in condizioni specifiche. La discretizzazione di superfici (pannellizazione sia Nurbs che Mesh), la modellazione delle geometrie attraverso informazioni (siano esse provenienti da dati di analisi ambientali, da mappe di colore o da database), l’estrazione e la gestione di informazioni richiedono la comprensione delle strutture dei dati al fine di definire un processo che va dalla progettazione alla costruzione.I partecipanti impareranno come costruire e sviluppare strutture di dati parametrici per informare geometrie ‘data-driven’ e come estrarre le informazioni rilevanti da tali modelli per il processo di costruzione.Modulo 2Il workshop, volto a promuovere le nuove tecnologie digitali di supporto alla progettazione e alla fabbricazione, fornirà ai partecipanti gli strumenti per la preparazione, attraverso Grasshopper, dei modelli per il processo di stampa 3d. Il workshop inoltre, darà ai partecipanti i fondamenti dell’uso della stampante 3d e si concluderà con la fabbricazione del proprio modello realizzato durante il corso.
[.] Date:Modulo 1 – 25/26/27 Luglio 2014 – SiracusaModulo 2 – 28/29 Luglio 2014 – Catania
[.] Tutors:Arch. Andrea Graziano (Co-de-iT)Arch. Salvo Pappalardo (Studio Aion)Arch. David Montenegro (Hackspace_Catania)
[.] Luogo:Modulo 1Officina Ermocrate – Viale Ermocrate 7, 96100 – SiracusaModulo 2Hackspace_Catania – Via Grotte Bianche, 112 – Catania
[more info]
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