requires four weather data inputs: air temperature (_dryBulbTemperature), relative humidity (relativeHumidity_), wind speed at 1.1 meters from the ground (windSpeed_) and mean radiant temperature (meanRadiantTemperature_).You can add values to the first three inputs from the Ladybug "Import Epw" component. For the last (meanRadiantTemperature_), you can add it from Ladybug's "Outdoor Solar Adjusted Temperature Calculator" component, or let "Thermal Comfort Index" component to calculate it. Both use different methods to calculate the final values.
I attached an example file below with second option.For more precise calculations you can use Honeybee and Chris' microclimate maps.An icing on the cake for the end: one of Ladybug developers yesterday released a set of Ladybug components for modelling in ENVI-met application. ENVI-met is cutting-edge microclimate software, which can be downloaded for free. It opens a number of advanced new analysis in outdoor domain, which couldn't have been done with the current Ladybug+Honeybee tools. So you can perform the simulation in ENVI-met 4 free software, and then add mean radiant temperature values from ENVI-met simulation to "Thermal Comfort Indices" component. Here is an example file.If you would like to go with the last approach, then the best would be to post a question about it in this topic.
1) You can make a polygonized tree.I haven't subtracted the trunk from the crown, but I guess it makes sense that it can be done.2) In most solar related simulations, a default albedo value of 0.2 is used. This corresponds to average albedo value taken from materials surrounding the urban or countryside location (concrete, grass, gravel, sand, asphalt...). However the presence of snow can significantly magnify the average albedo value several times. "Sunpath shading" components albedo_ input has an ability to calculate albedo due to presence of snow, if nothing is added to it (to albedo_ input). As you are performing the analysis of PET in a horizontal plane, it will not affect your calculations.3) Most thermal comfort indices will require performing analysis at 1.1 meters above the ground. This is considered to be height of standing person's gravity center.The same goes for PET index. So you are correct: you should place the analysis grid at 1.1 meters above the ground before adding it to the "Sunpath Shading" component.It is worth mentioning that "Thermal Comfort Indices" component used in this topic's PET_on_Grid2.gh and PET_on_Grid3.gh files is from last year, and much slower than the newest one (VER 0.0.64 MAR 18 2017) used in the example attached below. Just a remainder if you have been using older version of this component.Let me know if I misunderstood some of your questions, or if I missed to answer some of them.
EDIT: sorry for posting a double reply. When I posted it the first time, I only got links visible, with no text. Something has been wrong with grasshopper ning forum for the last couple of months.…
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
…
hope this number will grow in future. Currently available features are:
1) Creation of 2d or 3d context for any kind of building related analysis: automatically generate the 2d/3d surrounding buildings for the location where you would like to perform visibility, solar radiation, cfd or any other type of analysis. You need some other plugin for the last three, like Ladybug. It only creates the context=surroundings! The "automatic generation" process also includes creation of the local topography (terrain) along with buildings.
2) Identification of certain 2d or 3d elements in the created context. For example: selection of all hotels, parks, hospitals, restaurants, residential buildings etc.
3) Performing direct terrain analysis (hillshading, slope, ruggedness, roughness, water flow...)
4) Creation of terrain shading masks and horizon files for further solar and photovoltaics analysis.
Gismo will be very grateful if he could get any suggestions, improvements, bug reports and testing in the following period. In case you are willing to provide any of these, the requirements, installation steps and .gh example files can be found here, here and here.
Thank you in advance !!…
Added by djordje to Gismo at 9:10am on January 29, 2017
he example file to this file so you can give it a try with any version of Honeybee that you're already using. The only requirement is to have OpenStudio installed as the component is using OpenStudio libraries to parse gbXML files. If you're using the latest version available on github the component is also available under WIP tab.
Why?
The main purpose of developing this component is to save time and effort for importing Revit models for energy and daylight analysis. It bothers me to see a lot of smart people spend a lot of time to just come up with solutions just to get the geometry from Revit to Honeybee for analysis. This component is not solving all the issue but is a first step forward. In an ideal world, the future version of Honeybee, which works both under DynamoBIM and Grasshopper should address this issue but that can take some time to be fully ready!
How?
To use this component you need to Export your Revit model as gbXML and then use the file path to load the file into Grasshopper. There are several resources available online on how to prepare the analytical model in Revit and export the gbXML file. Here is an image for importing the Revit 2017 sample model using the default settings. As you can see the model will be just as good as what your original gbXML file from Revit is.
What can be improved?
Well, there are several items that can be improved and they are mostly not on us. To get it started I add what I think are the 3 main shortcomings and my thoughts on how they can be addressed in the future. Feel free to add what you think needs to be added to this list in the comments section.
1. Revit analytical models and as the results gbXML files, by design, are not intended to be clean. Watch this presentation from the Autodesk University to see the logic behind this approach which in short is it doesn't matter for a large scale early stage energy model. Well, This will be quite a problem for studies that you can do with Honeybee. Included but not limited to daylight and comfort analysis.
The best solution that I can think of, until Autodesk fixes their exporter, is to use Revit Rooms and Spaces and generate a clean model from the scratch. We have already tried this approach in Revit but since the Revit API doesn't provide access to Room openings we had a very hard time to get it to work.
That's why that I opened an idea on Revit ideas to get over this issue. With your support we already have 81 votes, but it hasn't been enough to make them to consider the idea for an official review. If you haven't voted already and you think this will be a helpful feature take a moment and vote so we can have it implemented at some point in the future.
2. There is no way (that I know) to export only part of the model. The way export gbXML is set up in Revit is to export the whole model once together. As a result, if you have a huge model with 100 rooms and you want to get one of the rooms into Honeybee using this component you have to export the whole model, which can take some time, and then import them all back into Grasshopper. To partially address this issue I added an input to the component that allows you input a list of names for rooms that you're interested to be loaded into Grasshopper. You can use the name of the room/space in Revit as an input for the component.
3. The component doesn't import adjacencies, loads, schedules and HVAC systems. I wasn't able to export a gbXML file from Revit with any of this data except for the adjacency, but even if you can do that, the component currently can only import geometries and constructions. I hope we get access to 1 and so we don't have to use the xml file approach at all, but if that takes a very long time then we will add these features to the component.
Happy 2017!
Mostapha…
eather data so it cannot be easily compared to Archsim. My account of the differences between Honeybee and Archsim will be far from complete but here are the key ones that I am aware of:
1) This difference is a bit of a superficial one but points to a deeper thinking about how the software should be used. Honeybee has many more components than Archsim, which means that Honeybee has a steeper learning curve than Archsim and will take longer to master. Along with this, you may also encounter a general mentality in the Honeybee community that "you should not be running a certain type of simulation unless you know how it works" whereas I know that Archsim is a bit more amenable to making things fast and easy to set up even when you are not sure what is going on under the hood. However, as a result of the large number of components in Honeybee, it is more open-ended, customizable, and includes more freedom in terms of cases that you can run and the parameters of the energy simulation that you can change than Archsim. You will also notice that, while there is a general ethos in the Honeybee community that you should not be running certain simulations unless you know what you are doing, we try to provide you with many resources to educate yourself if you are motivated. For example, we have long component descriptions that we assemble into documentation books like this (https://www.gitbook.com/book/mostapharoudsari/honeybee-primer/details), hours of video tutorial playlist like this one (https://www.youtube.com/playlist?list=PLruLh1AdY-SgW4uDtNSMLeiUmA8YXEHT_), and many GH example files on a github-based file sharing system (https://hydrashare.github.io/hydra/index.html). Not to mention a community of people who would respond to discussions like this one.
2) Archsim as a standalone application will soon be no more and will be instead distributed with the DIVA daylight analysis tool (http://diva4rhino.com/). While I am unclear on the exact trajectory of DIVA, it currently has a price tag attached to it and so I would assume that the future of Archsim will also carry this price tag. On the other hand, Honeybee and any derivative software will forever be free and open source under the GPL licence (https://github.com/mostaphaRoudsari/Honeybee/blob/master/License_Honeybee_GPL.txt).
3) This third point is a bit of a reiteration of the last one but Honeybee is open source, meaning that, if you need a feature of EnergyPlus that is not yet implemented on either interface, you can usually add it in yourself with a few lines of python code in Honeybee. This type of workflow is not possible with Archsim since it is closed source and requires you to use EnergyPlus's text editor interface after Archsim has exported an IDF in order to implement any additional EnerygPlus features.
4) The libraries and templates for Honeybee come from OpenStudio - the open source interface for EnergyPlus (https://www.openstudio.net/), which is supported by the US Department of Energy (just like EnergyPlus). Since Honeybee is open source, it is able to make use of the large database of building type schedules/loads and constructions that have been assembled by the OpenStudio team over the last several years as well as OpenStudio's SDK. I can also say that almost all of the development efforts of the Honeybee team are now focused now on integrating efforts with OpenStudio, including an exporter from Honeybee to OpenStudio that should be fully functional for the next stable release. I am not certain of the current extent of Archsim's libraries but, last I had checked, the creator was pulling them from his own experience and, as such, only had a few libraries to choose from. For all of my knowledge, through, this may be changing with the integration of Archsim with DIVA.
Let me know if this is helpful and, if anyone has more up-to-date knowledge on Archsim than I, please post there.
-Chris…
n the z axis I can not, here's the problem, because the movement is not only on the z axis, I can't do a serie with this vector. I tried to do it by differents columns or rows but its impossible for me.
2. Another problem. How I can fill a surface like this with tetrahedrons? What about change the size of this tetrahedrons? Is it possible like a fractal? :Si'm still working...
Thank you!
Finally I have completed the cloud!! I am a little bit fool. With the help of some sketches it was not so difficult! :).
I found the movement pattern of my tetrahedrons
Then I found the points inside my surface!
But now I cant create lines between points like in the begining of the process, with the pattern with points 1, 2, 3, 4. What I have to do?
??????????
Bye!!!…
t. This was a reasonably effective workflow for the purposes of solving the initial problem. (in reviewing this post, it seems a bit lengthy, but hopefully it's of use to others).
Link to Illustrator Script example:https://forums.adobe.com/thread/508138
Portion I used: This applies to entire illustrator document. I am using Illustrator CC 64 bit and this worked okay. Tested a few times and it failed once, but a restart of Illustrator fixed it.
var v_selection = app.activeDocument.pathItems;SwapFillStroke(v_selection); function SwapFillStroke(objSel) { for(k = 0; k < objSel.length; k++){ var subSel = objSel[k]; var c_fill = subSel.fillColor; var c_stroke = subSel.strokeColor; subSel.fillColor = c_stroke; if(!subSel.stroked) subSel.stroked = true; subSel.strokeColor = c_fill; }} redraw();
My goal was to export colored geometry, (analysis meshes for example), from Rhino and get it into illustrator with solid fills.
If you want to know how meshes are colored in rhino...there are many explanations here on the forum, a quick search will get you more detailed information.
Short version: export your lines from rhino to illustrator and run the script listed above to make the stroke color the fill color. (in illustrator, shift+X will swap the fill and stroke colors on individual objects, but does not work on multiple objects..hence the need for the script).
Detailed Version:
In my case, I had 2 case studies I was working with.1 - wind rose meshes generated from Ladybug/honeybee2 - A mesh terrain that was colored by pre-set slope values.
NOTE: There are a few plugins to bake objects with color. I used Human tools, (Bake Geometry and JustifiedText3D).http://www.grasshopper3d.com/group/human (lots of other great stuff in there too!)
I had two types of geometry. (2 different definitions)
1- An analysis mesh, (HoneyBee/LadyBug),
2 - Lines generated from mesh faces. (mesh terrain/slope values).
Export results as a DXF, and choose "do not explode". (these were my settings)
DXF seemed to produce the most consistent results.
(you could export/save as an AI file and just open them in illustrator, but that seemed to give inconsistent results with the script).
Open DXF in Illustrator:
Apply Script in illustrator:
In the terrain example, there are only 5 colors, so selection in illustrator, by color, is very easy. In the results from honeybee/ladybug, (or any analysis process I imagine), the default colors are created with a much wider range of values. I presume the legend is then created by an average of those values within a range. My point is that, with the analysis results, selecting objects by color in Illustrator is probably not a very effective workflow.
I only tested this on my instance of rhino and Illustrator. mileage may vary.
In summation, at this point, it seems that the best way to get colored mesh faces, into illustrator, is to export the meshes, (which really ends up being the mesh face edges...curves), and bringing them into illustrator and running a quick script to swap the colors. Once that is complete, you can then select ALL the objects, and change the stroke color/weight at once.…
URBS cup surface, and boy oh boy did it ever work more uniformly than using 3D orb cutters on a 3D cup. Different sized spheres return the *same* hex grid only less and less raised up as the spheres get very large.
My first question is whether these are different in character or just in Z scaling, so if I rescale them all to the same Z thickness, after extracting only the relief structure via Boolean union and splitting...and they are only *slightly* different in character, which means mere Z re-scaling of a single moderate ball size relief is an appropriate cheat to avoid slow Boolean union re-making each relief Z scale with different sized balls.
The one on the right is a very shallow relief scaled up to the same Z thickness as the pure sphere one on the left. And really, we will be mostly scaling *down* from a thicker master surface so that will attenuate any weirdness in the curvature. Indeed, I see no difference, so it makes sense to only archive the thickest one so we can control the full range of thicknesses, all the way to nearly flat bulbs. Here is the thickest one, just before the balls lose holes between them, scaled down compared to a shallow one made with huge balls to start with:
Now we just use Rhino Flow Along Surface or the Grasshopper Jackalope plug-in Sporf to morph this flat system onto our lathe form.
With Rhino history for the Flow Along Surface step I can rescale the original in Z and wait twenty seconds to see the update:
There are sad edge artifacts that will require some strategy to retain or later delete a whole row:
Maybe add more geometry to later delete or make a solid to hold stuff together?
So vastly decreasing the cell count and changing grid direction to match your cup:
The edges came out fine on this one, happily. The isocurve count has been increased by the Flow Along Surface command:
It can't be filleted yet since the joint where the cup NURBS surface has a joint now leaves feathery edges, so I went back and duplicated the border of the flat array, offset and lofted to make a protecting surface:
But that gave crazy artifacts:
I'm just going to use symmetry to fill in the joint with good faces that are not having to be joined as two halves. I had to turn my Rhino units tolerance down from a silly 0.0001 to 0.01 units to get a good re-join, but it still won't fillet without leaving holes.
SO LET'S FILLET THE FLAT THING. Same problem but a bit faster, and actually repairable manually. Rhino 5 is buggy as hell with core commands, damn it. This is not world class behavior.
Let's try it in Rhino 6 WIP, our great hope of the future: nope, the same. I had to simply manually copy the missing pieces from where it did work, which at least is easy to do in flatland. Now I get a cup:
This can *all* be done quickly in Rhino without Grasshopper, and Rhino affords you fast cage editing of the original flat array that Grasshopper cannot yet do. You just need to use Analyze Direction to be able to swap UV directions of the source or target and flip the source surface to achieve concave vs. convex patterns.
Grasshopper doesn't even have a fillet (multiple) edges component so there's not a lot of advantage to having some super slow parametric system via Grasshopper. It's not like you'll be able to see the changes fast enough to tweak a design.…
/www.grasshopper3d.com/forum/topics/vb-vs-c-vs-python
http://www.grasshopper3d.com/forum/topics/which-programming-language-should-i-focus-on-vb-or-python
VB.Net and C#
VB.Net and C# both belong to the ".Net" family of languages, and the things you can do with them in Rhino/Grasshopper are nearly 100% equivalent. Grasshopper itself was written in a combination of VB.Net and C#. Some advantages/comments, in no particular order:
Performance - VB.Net and C# scripts tend to execute faster because they are "Just-in-time" compiled as opposed to interpreted.
Autocomplete - both VB.Net and C# have rich autocomplete functionality in their respective script editor components - significantly more so than the python editor. This can be helpful for beginners since you can "hunt" for methods and properties by just typing a "." after an object name and looking at the list of available methods/properties.
Native Component development - If you eventually want to develop GHA assemblies/plug-ins for grasshopper, as of Rhino 5 you will have to use one of these two languages. However, there are plans to introduce python-based plugins in Rhino 6. Even so, the resources around plug-in development are very rich in the C# and VB.Net environments (with c# seeming to be the more popular of the two).
"Strong Typing" - VB.net to some degree, and C# especially, are less "forgiving" languages than python - they require you to know about the data type of the objects you're operating on. This can sometimes result in more verbose code - as you explicitly convert from type to type - but it also promotes good programming practice and helps make errors more understandable.
.Net ecosystem - using a .Net language means you have access to the thousands of libraries publicly available, and the process of referencing these libraries and making use of them is comparatively straightforward relative to python. More on this in the following section.
Resources/Support - At least as of 2012, VB and C# turned up more results on this forum than python, and I think you'll find slightly more expert-level coders in those languages able to help you here.
Which one between the two? C# or VB.Net? - Personally, I greatly prefer C# - I find it to be cleaner and clearer to use. I also have some programming background in C++/Java/Processing so I found the "C family" approach to be more familiar. As David and Damian point out in some of the posts linked above, C# is more popular than either python or VB.net in the rest of the coding world. However, if you are learning without any prior programming experience you may find VB.net to be a bit easier to learn.
Python
Python is, without a doubt, a beautiful and elegant language, which is probably more than can be said for VB.Net/C#. It is very popular with beginner coders, and its syntax is more readily understandable.
Syntax - Python is beautiful to read and write. Its syntax is very clear and free of extraneous punctuation (for example the ";" line endings in c#). It has many very nice language features that make common tasks more concise, like its loop syntax, list comprehensions, list "map" and "filter."
Multiple ways to talk to Rhino/Grasshopper - Python enables two general approaches to interacting with the Rhino/Grasshopper environment: RhinoCommon and RhinoScriptSyntax. If you have prior experience with Rhinoscript, you may find RhinoScriptSyntax to be preferable - it adapts many of the methods you're familiar with to the python language, and simplifies some tasks. A word of caution though - working with Rhinoscriptsyntax can introduce a performance hit relative to RhinoCommon operations. C# and VB.net by contrast can only work with RhinoCommon.
"Goodies" - The Python environment in Grasshopper has some "special features" that the other languages lack. In particular, the "GHPythonLib" library enables the ability to call most Grasshopper components from within your code, and the ability to easily enable parallel processing to improve performance. (A word of caution though - these two features do not seem to "play well" with each other, there may be bugs causing memory leaks that result in increasingly worse performance with each execution).
Cross-Platform - Unlike C#/VB.net, Python can be used natively in Rhino for Windows and Rhino for Mac.
Direct scripting in Rhino - You can also use Python directly in the Rhino environment without the need for Grasshopper if you desire, using the Rhino Python editor.
IronPython / Ecosystem issues - one frustration / potential downside to working with Python for Rhino/GH is that though there is a vast, amazing ecosystem of external libraries for Python, getting these to install/work properly in the Rhino/GH environment can be a real pain - largely because the language is actually "IronPython," a version of python designed to work closely with the .Net ecosystem. Many popular libraries like numpy and scipy are very challenging to get working in Rhino/GH.
Scripting in other programs - Especially in the AEC industry, Python is a popular scripting language for other applications. Tools like Revit, Dynamo, Blender, and ArcGIS all offer their own Python scripting interface - so learning Python in Rhino/GH can give you a leg up in eventually scripting in these other programs.
Python's Stock is Rising - there are currently a number of efforts to improve the "status" of python within the Rhino/GH ecosystem. The python editor in Rhino 6 has a number of improvements, not least of which is the ability to "compile" add-ons for Grasshopper written in python. I'm sure Giulio can speak to other upcoming improvements.
I hope this summary helps you find the right option for you. Ultimately you can't go wrong; concepts from any of the available scripting languages will make it much easier to learn the next one. In my day to day work I use a combination of both C# and python, where appropriate, and I love them both.
I hope others will feel welcome to chime in on this FAQ and add their own thoughts about advantages/disadvantages of these various options! If you have time, read through some of the other posts linked to at the beginning - there's lots of additional great information there. …
ndard length elements without any cutting, and using only simple connections, such as cable ties or scaffold swivel couplers.
To summarize the approach I present here:
Design an initial shape
Remesh this form so that the edges are all roughly the length of the tubes we will use to build the structure
Rotate and extend the edges of this mesh to create the crossings
Apply a relaxation to optimize the positions of the tubes for tangency
demo_reciprocal_structures.gh
Initial form
In this example I show how to apply this system to a simple sphere. You can replace this with any arbitrary shape. It can be open or closed, and have any topology.
Remeshing
The new ReMesher component takes an input mesh, and a target edge length, and iteratively flips/splits/collapses edges in order to achieve a triangulated mesh of roughly equal edge lengths.
Press the Reset button to initialize, then hold down the F5 key on your keyboard to run several iterations until it has stabilized. (F5 just recomputes the solution, and this can be a quick alternative to using a timer)
Once the remeshing is complete, bake the result into Rhino and reference it into the next part of the definition (I recommend doing this rather than connecting it directly, so that you don't accidentally alter the mesh and recompute everything downstream later).
Alternatively you can create your mesh manually, or using other techniques.
Rotate and Extend
We generate the crossings using an approach similar to that described by Tomohiro Tachi for tensegrity structures here:
http://www.tsg.ne.jp/TT/cg/FreeformTensegrityTachiAAG2012.pdf
Using the 'Reciprocal' component found in the Kangaroo mesh tab, each edge is rotated about an axis through its midpoint and normal to the surface, then extended slightly so that they cross over.
By changing the angle you can change whether the fans are triangular or hexagonal, and clockwise or counter-clockwise.
Choose values for the angle and scaling so that the lines extend beyond where they cross, but not so far that they clash with the other edges.
Note that each rod has 4 crossings with its surrounding rods.
There are multiple possibilities for the over/under pattern at each 'fan', and which one is used affects the curvature:
A nice effect of creating the pre-optimization geometry by rotating and extending mesh edges in this way is that the correct over/under pattern for each fan gets generated automatically.
Optimization for tangency
We now have an approximate reciprocal structure, where the lines are the centrelines of our rods, but the distances between them where they cross vary, so we would not actually be able to easily connect the rods in this configuration.
To attach the rods to form a structure, we want them to be tangent to one another. A pair of cylinders is tangent if the shortest line between their centrelines is equal to the sum of their radii:
Achieving tangency between all crossed rods in the structure is a tricky problem - if we move any one pair of rods to be tangent, we usually break the tangency between other pairs, and because there are many closed loops, we cannot simply start with one and solve them in order.
Therefore we use a dynamic relaxation approach, where forces are used to solve all the tangency constraints simultaneously, and over a number of iterations it converges to a solution where they are all met. The latest Kangaroo includes a line-line force, which can be used to pull and push pairs of lines so that they are a certain distance apart. Each rod is treated as a rigid body, so forces applied along its length will cause it to move and rotate.
The reciprocal component uses Plankton to find the indices of which lines in the list cross, which are then fed into the force for Kangaroo. We also use springs to keep each line the same length.
If the input is good, when we run the relaxation (by double clicking Kangaroo and pressing play), the rods should move only a little. We can see whether tangency has been achieved by looking at the shortest distance between the centerlines of the crossing rods. When this is twice the rod radius, they are tangent. Wait for it to solve to the desired degree of accuracy (there's no need to wait for 1000ths of a millimeter), and then press pause on the Kangaroo controller and bake the result.
The radius you choose for the pipes, curvature of the form and length of the edges all affect the result, and at this stage you may need to tweak these input values to get a final result you are happy with. If you find the rods are not reaching a stable solution but are sliding completely off each other, you might want to try adding weak AnchorSprings to the endpoints of the lines, to keep them from drifting too far from their original positions.
For previewing the geometry during relaxation I have used the handy Mesh Pipe component from Mateusz Zwierzycki, as it is much faster than using actual surface pipes.
To actually build this, you then need to extract the distances along each rod at which the crossings occur, and whether it crosses over or under, mark the rods accordingly, and assemble (If there is interest I will also clean up and post the definition for extracting this information). While this technique doesn't require much equipment, it does need good coordination and numbering!
There is also a ReciprocalStructure user object component that can be found in the Kangaroo utilities tab, which attempts to apply steps 3 and 4 automatically. However, by using the full definition you have more control and possibility to troubleshoot if any part isn't working.
The approach described here was first tested and refined at the 2013 Salerno Structural Geometry workshop, lead by Gennaro Senatore and myself, where we built a small pavilion using this technique with PVC tubes and cable ties. Big thanks to all the participants!
Finally - this is all very experimental work, and there are still many unanswered questions, and a lot of scope for further development of such structures. I think in particular - which of the relative degrees of freedom between pairs of rods are constrained by the connection (sliding along their length, bending, and twisting) and how this affects the structural behaviour would be interesting to examine further.
Steps 3 and 4 of the approach presented above would also work with quad meshes, which would have different stability characteristics.
There is also the issue of deformation of the rods - as the procedure described here solves only the geometric question of how to make perfectly rigid straight cylinders tangent. The approach could potentially be extended to adjust for, or make use of the flexibility of the rods.
I hope this is useful to somebody. Please let me know if you do have a go at building something using this.
Any further discussion on these topics is welcome!
Further reading on reciprocal structures:
http://vbn.aau.dk/files/65339229/Three_dimensional_Reciprocal_Structures_Morphology_Concepts_Generative_Rules.pdf
http://www3.ntu.edu.sg/home/cwfu/papers/recipframe/
http://albertopugnale.wordpress.com/2013/04/05/form-finding-of-reciprocal-structures-with-grasshopper-and-galapagos/
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