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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, W(est), N(orth) (2 more are required if we want top-bottom children).
Since each child Box has his faces oriented the same way the location rule applies to all.
The only other thing is to realize that for an item positioned, say, South it can have children in any orientation except the straight opposite (North) ... etc etc.
Therefor for a 3d/2d hexagon you'll need 6 orientations (S, SE, NE, N, NW, SW) ... but clash checks are more paramount than in the rectangle/cube case. …
have the first output variable.
If you have the out parameter showing then it copies fine.
2. If you select the "Show "code" input parameter" the component bugs out. Error message is "Warning: no script to execute".
Open Editor and Test your script to remove error
(Just saying: new way to rename, add, delete output and input parameters is really nice!)…
Added by Jake Hebbert at 11:44am on December 8, 2012
dient in this diagrid (size). Now my main issue is, 1, is it possible to convert this mesh into surface in rhino; 2, is it possible to do it in rhino or it should be done in maya w/ maya paint and script? (which I find here, but not sure how it was achieved [http://computationalmatter.com/P-aintermetric]
Please let me know if there's any suggestions. Thanks
…
edzy? Ile nas jest?Na nasze pierwsze spotkanie zapraszamy wszystkich, którzy używają GH w pracy projektowej. Liczymy na przygotowanie 5-minutowych prezentacji o tym nad czym pracujecie. Na ich zgłoszenia czekamy do 7-mego stycznia.Koniecznie zaproście Waszych znajomych.Miejsce spotkania zależeć będzie od frekwencji.Do zobaczenia wkrótce.
[eng]
Warsaw Grasshopper scene is booming! Each months there are more and more GH geeks. Now it is time to meet. Architektura Parametryczna invites all Grasshopper users to meet and discuss on what we work.We invite everyone to prepare 5-minute, Pecha kKucha-like, presentation.
See you soon!
Adrian
Please RSVP.…
IF the platform is "unsuitable" (or there's others more suitable) then disproportional amount of effort is obviously required for the same sort of result (or "similar"). And well ... er ... if the design goal is solid modelling ... chances are that a surface modeller MAY classify as unsuitable (but may not depending on the case).
Given the opportunity: Personal data: strictly AEC sector, AECOSim/Microstation (25 years, main BIM/General CAD purpose app) + various vertical Bentley Systems AEC apps + Generative Components (~10 years, main Parametric app) + CATIA/NX (20 years, main MCAD app) + Quest3D (~10 years, main VR app) + ... + you name it.
UGLY news: I run a practice > this means that I'm used in evaluating/addressing problems having TEAMS in mind, budget, alternatives, deadlines, clients, study guarantees, claims, clauses ... > this means that I'm often very bad/off-topic if an one man show task requires some opinion/solution/workflow.
Anyway ...
... with regard your issue I'll provide an indicative approach after this w/e ... but chances are that would be carried over exclusively without native components.
best, Peter
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of similar/WOW buildings that failed (or leaked) including a very famous one.
2. You must use instance definitions for the truss parts (sleeves, cones, rods and the likes) otherwise the whole thing could become an unworkable nightmare.
3. You must address clash issues otherwise doing it is out of question. These affect the skin parts as well (but as I said: this is 100% pro territory).
4. Your structural analysis (in order to make any sense) must deal with real life components either commercially available or bespoke things designed for the specific project.
5. Wind/Seismic effects can cause skin component issues/failures/leaks as it happened ... well ... in a variety of contemporary famous buildings.
6. Vapor condensation yields (in most of similar cases) buildings that "rain from the inside" - nothing serious, mind: just have an umbrella ready.
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pecific character it encounters in the file a specific curve would be created (a line with a particular length/orientation associated with that specific character) whose starting point is on the end of the last previous line. here is simple action list:
read first character in txt file
identify character (number 20 in attached example)
insert line associated with character (1" horizontal line)
read next character in txt file.
identify character (number 8 in attached example)
start curve (specific curve associated with the number 8 (1.25" vertical line)) on the end of the previous line.
read next character in txt file.
identify character (number 5 in attached example)
start curve (specific curve associated with the number 5 (.25" horizontal line)) on the end of the previous line.
etc
loop repeats till end of txt file.
i am good with everything else (linking the file, building curves on the ends of things, creating line parameter w/ persistent data, etc) but I'm having a problem with the "if/then" nature of the project. I haven't found a component that has this sophistication yet... I've tried the equals component that compare lists and identify true/false scenarios and the f(x) along with dispatch to create a curve if a single situation occurs (like if x>3, then make a circle) but what about the next character?
I am wondering if I should do this in C+ (which I also don't know) but would rather create this in grasshopper.
See attached for example grasshopper file and txt file.
I would really appreciate any help you can offer - Thanks!!!
// jon…
Added by jon kuzmich at 11:14pm on September 14, 2013