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
…
rtitions." (http://wias-berlin.de/software/index.jsp?id=TetGen&lang=1)
To continue with my wrapping career, TetRhino (or Tetrino) is a .NET wrapper for the well-known and pretty amazing TetGen mesh tetrahedralization program. It provides one new GH component for discretizing or remeshing objects using TetGen. Basic tetrahedralization functionality is exposed with a few different output types that can be controlled. At the moment, the only control for tetrahedra sizes is the minimum ratio, which is controlled by a slider. This is hardcoded to always be above 1.0-1.1, as it is very easy to generate a LOT of data (and crash)...
The libs are divided again into different modules to allow flexibility and fun with or without Rhino and GH, so have fun. All 4 libs should be placed in a folder (maybe called 'tetgen') in your GH libraries folder. Remember to unblock.
Once again, the libs are provided as-is, with no guarantee of support for now, as I use them internally and do not intend to develop this into a shiny, polished plug-in. If there is enough interest, I can tidy up the code-base and upload it somewhere if someone more savvy than me wants to play.
TetgenGH.gha - Grasshopper assembly which adds the 'Tetrahedralize' component to Mesh -> Triangulation.
TetgenRC.dll - RhinoCommon interface to the Tetgen wrapper.
TetgenSharp.dll - dotNET wrapper for Tetgen.
TetgenWrapper.dll - Actual wrapper for Tetgen.
Obviously, credit where credit is due for this excellent and tiny piece of software:
"The development of TetGen is executed at the Weierstrass Institute for Applied Analysis and Stochastics in the research group of Numerical Mathematics and Scientific Computing." See http://wias-berlin.de/software/index.jsp?id=TetGen&lang=1 for more details about TetGen.
To wrap up, some notes about the inputs:
These are the possible integer Flags (F) values and resultant outputs for the GH component:
0 - Output M yields a closed boundary mesh. Useful for simply remeshing your input mesh.
1 - Output M yields a list of tetra meshes.
2 - Output I yields a DataTree of tetra indices, grouped in lists of 4. Output P yields a list of points to which the tetra indices correspond.
3 - Output I yields a DataTree of edge indices, grouped in lists of 2. Output P yields a list of points to which the edge indices correspond. Useful for lots of things, very easy to create lines from this to plug into K2 or something for some ropey FEA (or not so ropey!) ;)
As this component can potentially create a LOT of data, especially with dense meshes, care should be taken with the MinRatio (R) input. This will try to constrain the tetra to be more or less elongated, which also means that the lower this value gets, the more tetra need to be added to satisfy this constraint. Start with very high values and lower them until satisfactory.
Hopefully shouldn't be an issue, but it's possible that you need the 2015 Microsoft C++ Redistributable.
Happy tetrahedralizing...
UPDATE: The tetgen.zip has been updated with some fixes.
UPDATE2: This is now available on Food4Rhino: http://www.food4rhino.com/app/tetrino
…
Added by Tom Svilans at 1:27am on October 24, 2017
.com/forum/topics/use-pythoneditor-to-run?commentId=2985220%3AComment%3A138538
For now I am considering a simple test case in which a set of sliders are added together into a GH_number component called "output":
I am finding that from the Rhino Python Editor it is definitely possible to change the slider values and retrieve results in a loop. Below I copied the code that runs from the Rhino Python Editor, where I simply change the slider value of the slider with Nickname "Number Slider1" from 0 to 2. (note that grasshopper and the testfile are already open in this example)
This script prints out the following results as expected:
Slider value: 0.0Result value: 1.154Slider value: 1.0Result value: 2.154Slider value: 2.0Result value: 3.154
However using the exact same code in a GHPython component within Grasshopper the Grasshopper Python Script Editor's console reads:
Slider value: 2.0Result value: 3.154Slider value: 2.0Result value: 3.154Slider value: 2.0Result value: 3.154
It seems that the solver doesn't recompute during each iteration but just retrieves the final state of my script.
So basically I have been trying to trigger a 'runsolver' command inside my loop. I tried using the methods available trough the RhinoScript interface, as David describes here.
http://www.grasshopper3d.com/forum/topics/open-a-gh-automatically
I could create a loop looking like this:
But running this in the Grasshopper Component crashes Rhino. I have also tried this by Disabling the solver first using the DisableSolver() method. This does disable the solver but still Rhino crashes. Also I used the ExpireSolution(True) method on the slider object like:
However in this case I don't get any different results.
So I guess my question is simple:
Is there a way to recompute the solver after a slider change inside a GHPython script component during a loop?
Any suggestions, or references would be greatly appreciated!
(FYI: I am using Rhino5x64 and Grasshopper Version 0.9.0014, attached is the script I used both in the Rhino Python Editor and the GHPython component and the grasshopper file)…
ou will see all of the available components on a ribbon at once so there is no need to keep clicking drop down menus.
It's all about discoverability with GH. What if you're a beginner and don't know about the Create Facility (dbl click canvas) how can you find Extr?
Even if you hover over every component or use the drop down lists you will not see the name Extr appear anywhere.
Sure it makes sense that Extr is short for Extrude but it's also the Nick Name of Extrude to Point component
So you can easily miss the fact that one has a Distance Input verses a Point Input.
I think I made the move to Icons around about the move from version 0.5 to 0.6, possibly before. I initially thought that I would go back to text because I loved the mono chromatic look of the text but I soon realised that Icons were the way forward. The greatest benefit is speed. You don't need to digest and decipher every component (which is written 90 degrees to the norm).
I'm not saying you should move to Icons forthwith but at least consider that once you have a better knowledge and understanding of GH, Icons will set you free.
My top ten tips that I would highly recommend to anyone wanting to better themselves with GH.
1) Turn on Draw Icons
2) Turn on Draw Fancy Wires
3) Turn on Obscure Components
4) Use the Create Facility like a Command Line eg "Slider=-1<0.75<2" or "Shiftlist=-1"
5) Use Component Aliases to customise your use of the Create Facility eg giving the Point XYZ component an alias of XYZ will bring it up as the first option on the Create Facility as opposed to the other possibilities.
6) Try to answer other people's questions even if it's not relevant to your own area. By looking into solving a problem outside of your comfort zone and then posting your results it is very rewarding but it also lets you see the other approaches that get posted in a new light.
7) Take the time to understand Data/Path structures.
8) Buy a second monitor - There is nothing that can compare to real estate when working in Grasshopper.
9) Read Rajaa Issa's Essential Mathematics
10) Pick a panel in a tab on the ribbon and get to know every component inside and out and then move on. Start with the Sets Tab > List Panel…
curve or locus] of a segment AB, in English. The set of all the points from which a segment, AB, is seen under a fixed given angle.
When you construct l'arc capable —by using compass— you obviously need to find the centre of this arc. This can be easily done in GH in many ways by using some trigonometry (e.g. see previous —great— solutions). Whole circles instead of arcs provide supplementary isoptics —β-isoptic and (180º-β)-isoptic—. Coherent normals let you work in any plane.
Or you could just construct β-isoptics of AB by using tangent at A (or B). I mean [Arc SED] component.
If you want the true β-isoptic —the set of all the points— you should use {+β, -β} degrees (2 sides; 2 solutions; 2 arcs), but slider in [-180, +180] degrees provides full range of signed solutions. Orthoptic is provided by ±90º. Notice that ±180º isoptic is just AB segment itself, and 0º isoptic should be the segment outside AB —(-∞, A] U [B, +∞)—. [Radians] component is avoidable.
More compact versions can be achieved by using [F3] component. You can choose among different expressions the one you like the most as long as performs counter clockwise rotation of vector AB, by 180-β degrees, around A; or equivalent. [Panel] is totally avoidable.
Solutions in XY plane —projection; z = 0—, no matter A or B, are easy too. Just be sure about the curve you want to find the intersection with —Curve; your wall— being contained in XY plane.
A few self-explanatory examples showing features.
1 & 5 1st ver. (Supplementary isoptics) (ArcCapableTrigNormals_def_Bel.png)
2 & 6 2nd ver. (SED) (ArcCapableSED_def_Bel.png)
3 & 7 3rd ver. (SED + F3) (ArcCapableSEDF3_def_Bel.png)
4 & 8 4th ver. (SED + F3, Projection) (ArcCapableSEDProjInt_def_Bel.png)
If you want to be compact, 7 could be your best choice. If you prefer orientation robustness, 5. Etcetera.
I hope these versions will help you to compact/visualize; let me know any feedback.
Calculate where 2 points [A & B] meet at a specific angle is just find the geometrical locus called arco capaz in Spanish, arc capable in French (l'isoptique d'un segment de droite) or isoptic [curve or locus]
of a segment AB, in English. The set of all the points from which a segment,
AB, is seen under a fixed given angle.…
Meeting Agenda:
1) Discuss what the group would like to learn this term through our regular scheduled meetings. Topics include the priority and sequence of Grasshopper exercises we would like to explore during the winter term from http://www.digitaltoolbox.info/grasshopper_basic.html and Processing tutorials from the Processing Handbook I received from MIT.
2) Watch the Matt Storus Church Machine video and have a discussion about parametric and generative tools in design.
If you have a chance, please read the following article by Tim Love called Between Mission Statement and Parametric Model at:
http://places.designobserver.com/entry.html?entry=10757
3) Discuss a possible design build project over the following winter and spring terms using the skill set this group is developing. Conversation led by Chris Nielson (please see comments below for a brief backstory)
4) Discuss possible applied research and design work for the National Conference on the Beginning Design Student paper, Machine Craft and the Contemporary Designer: exploring parameters and variables through making physical artifacts. I wrote the attached abstract and submitted it for the conference the past fall and it was accepted. To continue with the research I need to assemble a team of students that will help explore the principles I set forth by making physical objects with the cnc router. In exchange for helping with the research I will show participants how to use the cnc router, how to author machine code and provide you with the cnc controller interface software necessary to simulate machine movements. Not to mention, your work will be sited in the research paper I present at the conference at UNC Charlotte in March. More tomorrow night, of course.
Thank you for your interest and I hope to see you there.
Sincerely,
Erik Hegre
Chris Nielson Reply by Eugene Parametric Society on January 7, 2010 at 12:02pm
All,
In response to Erik, who requested that I describe my intentions in a design-build project and to the article posted (definitely required reading for this group) I propose that we begin development of a project that spans the realm of "sustainable social" architecture and parametric design. The particulars of such a design do need to be made concrete, and it will be important to define the goals of such a project.
Therefore, I would suggest that this serve as a forum for the next few weeks for those interested in producing a built project. I agree with Nico that it may not be feasible to create the built piece, whatever it may be, this term; however we should have the groundwork and a plan in place by the end of the next 10 weeks.
Either way, I would ask that everyone who is interested to please provide as many concepts to this forum to begin a discussion. If you are indeed interested, please submit goals that this project could achieve (energy, socially, aesthetically, economically, related) and perhaps what you envision the project to physically be (shading device, public bench, water catchment, interactive thermal contraption, etc . . . )
I look forward to hearing your thoughts!
Cheers,
Christopher…
ración de 150 horas divididas en cuatro módulos, arrancando el 22 de Marzo del 2011 y terminando la segunda semana de Junio con sesiones los Martes y Jueves de 18:00 a 22:00hrs y algunos Sábados de 10:00 a 14:00hrs.
El tema central del diplomado es el uso integral de la herramienta digital en el proceso de diseño a partir de la base teórica del fenómeno de la emergencia (entendida como la obtención de resultados complejos a partir de la interacción de elementos simples con reglas de bajo nivel de sofisticación).
El desarrollo del programa se concentra en la aplicación práctica de las reflexiones teóricas generadas mediante el uso de herramientas digitales generativas, principalmente Grasshopper (plug-in de modelado parametrico para Rhinoceros).
Contaremos con la presencia de dos colaboradores internacionales: EL primero será un miembro de LaN (Live Architecture Network) que impartirá un curso sobre programación avanzada en Grasshopper enfocandolo a la realización de un objeto construido, haciendo énfasis en la transición entre lo virtual, lo análogo y lo físico. El segundo es Jalal el Ali, maestro en arquitectura por la Architectural Association, líder de la Unidad de Geometría Generativa de Buro Happold y actual líder de proyecto en Zaha Hadid Architects, quien dará un curso intensivo enfocado al uso de la herramienta digital y la producción digital, enseñando procesos que ha aplicado en la empresa donde trabaja. Jalal pronunciará también una conferencia magistral.
Es un programa promueve el uso de nuevas tecnologías y la integración de procesos de producción desde la concepción del diseño, aplicando los conocimientos teóricos en un objeto físico usando el laboratorio de fabricación de la Universidad Iberoamericana.
…
s, the participants will focus on the key advantages of Grasshopper’s capabilities through a range of design challenges in order to aid designers in both their drafting tasks and modelling capabilities.
The workshop covers many concepts such as Object Attributes/Parameters, Data Types, Data Structures, and Designing with Algorithms. Specifically, this course will focus on understanding both Lists and Data Trees, as well as the best practices for integrating Grasshopper into your Professional Design Workflow. The workshop offers guided curriculum and continuous support, based on in-depth and professional learning experiences.
Workshop outcomes:Teach the participants how to:-
+ be proficient in parametric logics learning the key benefits of parametric techniques in architecture design workflow (when to use it & how to use it)+ Correctly communicate with different 3D and BIM packages in order to keep the geometry clean and light while preserving all NURBS information.+ Develop architecture design based on mathematical equations to create non-standard free form building skin.+ Create a pattern that changes dynamically based on specific inputs which can be applied over the building façade, interior walls or ceiling or even floor pattern.+ Automate and Optimize design variables to achieve the optimum solution for the design problem.
Program Outline:
DAY 1:-Introduction to Parametric Design -Introduction to Grasshopper & Rhino (technical tools).
DAY 2:-Exploring the parametric workflow. -Setup the design algorithm & generating a list of data.
DAY 3:-Introducing the new ways of generating parametric curves and surfaces.-Parametric form generation in-dept
DAY 4:-Introducing Data Tree logic and parametric transformations.-Creating Associative techniques – Attractors (points, curves and vectors).
DAY 5:-Working with advanced form generation with dynamic pattern.-Parametric optimization based on environmental analysis -featuring the Performance-Driven Design possibilities
DURATION:6 – 8 hours per day [50 - 60 hours Total]Every Saturday [9.00 Am : 1.00 Pm & 2.30 Pm : 6.00 Pm]
PREREQUISITES:No need of any specific knowledge of Rhinoceros or Grasshopper.
REGISTRATION:In order to register, you will need to fill the Registration Form .https://docs.google.com/forms/d/1PckdW1hrWs9fJAHWBZlVsuhH8K0PfDuMWIpXHT_4FYw/viewform
REGISTRATION DEADLINE:23th October 2014.…
Added by ayman wagdy at 7:48am on October 19, 2014
cess informing the user the network is incomplete.
I've been thinking for a while about reading in these blobs of incomprehensible data in an attempt to maintain them through an open/save cycle, but I'll never be able to get this process watertight.
2) When you release components, you should try and make sure that they are backwards compatible previous releases. For example, if you decide to change the number of inputs/outputs or the type of inputs/outputs, this might well break file IO. What you should do in those cases is:
- Copy-paste the old component source code and change the ComponentGuid property. In essence, you make a different component which will have the changes.
- Change the Exposure property on the old component to be GH_Exposure.hidden. This will hide the component from the interface.
This basically means that when people open a file that uses the old style component, they'll get the old-style component. If people instantiate the component anew, they'll get the new component.
Grasshopper and it's default gha assemblies feature dozens upon dozens of these hidden components, sometimes there's as many as 4 old-style components out there.
3) If you want to store additional data in the ghx file for a specific component, you'll need to override the Read() and Write() methods. Something like this:
Public Overrides Function Write(ByVal writer As GH_IO.Serialization.GH_IWriter) As Boolean
writer.SetBoolean("MySpecialBooleanValue", m_myBoolean)
writer.SetString("MySpecialStringData", m_myString)
Return MyBase.Write(writer)
End Function
and
Public Overrides Function Read(ByVal reader As GH_IO.Serialization.GH_IReader) As Boolean
m_myBoolean = False 'Default state
m_myString = String.Empty 'Default state
reader.TryGetBoolean("MySpecialBooleanValue", m_myBoolean)
reader.TryGetString("MySpecialStringData", m_myString)
Return MyBase.Read(reader)
End Function
It is usually possible to make the Reading process smart enough to handle backwards compatibility. You can ask the reader object whether or not a certain value exists and you can then decide whether you can safely use old or new reading logic. So any changes to this part probably don't require you to create a duplicate component and hide the old one.
--
David Rutten
david@mcneel.com
Poprad, Slovakia…
Added by David Rutten at 2:34am on February 26, 2011