ld fabrication process for 1:1 components and assemblies. The event will be held in London at the RoboFold factory/studio from June 9th-12th. Workshop participants will investigate the design of facade forms in paper and card, and transfer these to Rhino's Grasshopper plugin to simulate folding and robotics. Using the in-house CNC vinyl cutter and CNC router, various scale prototypes will be folded by hand and by robot. The final 1:1 facade will be formed using 6-axis industrial robots.
Details:
-Tutors: Gregory Epps, RoboFold founder and Florent Michel, RoboFold software developer.-See previous workshops here. -Download Poster here.-Bring your own laptop. -Please install Rhino and Grasshopper before you arrive.-No previous experience with Grasshopper necessary.-Daily 10am-5pm. Location details here. -Drinks reception Tuesday evening.
Registration:
http://www.robofold.com/index.php?WEBYEP_DI=18
Professional: £600 inc VAT
Student: £500 inc VAT
Enquiries: info@robofold.com…
Added by Gregory Epps at 10:02am on April 17, 2012
complicated than it seems as I have an event and a subscriber method receiving data from a serial port.
In the code below, the strings received within myReceivedLines appear when connecting with the serial port (when connecttodevice is true). However they disapear when I launch another command (when homeallis true).
As you recommended in your reply, I have added the field called myReceivedLineswithin the class so that I could use the method String.Add() to all the feedback received and commands sent.
Why does the feedback dispear when a command is sent? Is the string going to myReceivedLine disappearing because they happen within a subscriber method or is it related to the DA.SetDataList() method used to assign myReceivedLinesto the output?
Many thanks!
public class SendToPrintComponent : GH_Component { //Fields List<string> myReceivedLines = new List<string>(); SerialPort port; //subscriber method for the port.DataReceived Event private void DataReceivedHandler(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { SerialPort sp = (SerialPort)sender; while (sp.BytesToRead > 0) { try { myReceivedLines.Add(sp.ReadLine()); } catch (TimeoutException) { break; } } } protected override void SolveInstance(IGH_DataAccess DA) { //Opening the port if (port == null) { string selectedportname = default(string); DA.GetData(1, ref selectedportname); int selectedbaudrate = default(int); DA.GetData(2, ref selectedbaudrate); //Assigning an object to the field within the SolveInstance method() port = new SerialPort(selectedportname, selectedbaudrate, Parity.None, 8, StopBits.One); //Enables the data terminal ready (dtr) signal during serial communication (handshaking) port.DtrEnable = true; port.WriteTimeout = 500; port.ReadTimeout = 500; } //Event Handling Method bool connecttodevice = default(bool); DA.GetData(3, ref connecttodevice); if (connecttodevice == true) { if (!port.IsOpen) { port.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler); DA.SetDataList(0, myReceivedLines); port.Open(); } } else if (port.IsOpen) { port.DataReceived -= new SerialDataReceivedEventHandler(DataReceivedHandler); port.Close(); } if (port.IsOpen) { DA.SetData(1, "Port Open"); } //If the port is open do all the rest if (port.IsOpen) { bool homeall = default(bool); DA.GetData(5, ref homeall); //Home all sends all the axis to the origin if (homeall == true) { port.Write("G28" + "\n"); myReceivedLines.Add("G28" + "\n"); DA.SetDataList(2, myReceivedLines); } } else { DA.SetData(1, "Port Closed"); } }}…
nd improvements. Many of the new features and components announced in the last release have become stable and have emerged from their WIP section. Additionally, after two years of work, we are happy to announce that we finally have full support of an OpenStudio connection within Honeybee, which has ushered in a whole host of new features, notably the modelling of detailed HVAC systems. As always you can download the new release from Food4Rhino. Make sure to remove the older version of Ladybug and Honeybee and update your scripts.
LADYBUG
1 - Solar Hot Water Components Out of WIP
After much beta-testing, bug-fixing, and general development, all of the Photovoltaic and Solar Hot Water components are now fully out of WIP! The main component is based on a Chengchu Yan's publication. Components have been added to Ladybug thanks to the efforts of Chengchu Yan and Djordje Spasic.. See Djorje’s original release post of the solar hot water components for more information on the components that just made it out of WIP.
2 - New Terrain Shading Mask Released in WIP
In addition to Djordje’s prolific addition of renewable energy components, he has also contributed a widely-useful component to generate terrain shading masks, which account for the shading of surrounding mountains/terrain in simulations. While initially added to assist the solar radiation radiation and renewable energy components, the component will undergo development to optimize it for energy and daylight simulations over the next few months. Another new component called Horizon Angles can be used to visualize and export horizon angles. You can test them out now by accessing them in the WIP section. For more information, see Djordje’s release post on the GH forum here.
3 - New Mesh Selector Component
After realizing that the Optimal Shade Creator component has applications to a whole range of analyses, it has now been re-branded as the Mesh Selector and has been optimized to work easily with these many analyses. Specifically, the component selects out the portion of a mesh that meets a given threshold. This can be the portion of a shade benefit analysis meeting a certain level of shade desirability, the portion of a radiation study meeting a certain level of fulx, the portion of a daylight analysis meeting a certain lux threshold, and much more!
4 - Solar Adjusted Temperature Now Includes Long Wave Radiation
Thanks to a question asked by Aymeric and a number of clarifications made by Djordje Spasic, the Solar Adjusted Temperature component now includes the ability to account for long-wave radiative loss to the sky in addition to it original capability to account for short wave radiation from the sun. As such, the component now includes all capabilities of similar outdoor comfort tools such as RayMan. The addition of this capability is also paralleled by the addition of a new horizontalInfraredRadiation output on the ImportEPW component. See the updated solar adjusted example file hereto see how to use the component properly.
5 - Support for both Log and Power Law Wind Profiles
In preparation for the future release of the Butterfly CFD-modelling insect, the Ladybug Wind Profile component now includes the option of either power law or log law wind profiles, which are both used extensively in CFD studies. Thanks goes to Theodoros Galanos for providing the formulas!
6 - New Radiant Asymmetry Comfort Components
Prompted by a suggestion from Christian Kongsgaard, Ladybug now includes components to calculate radiant asymmetry discomfort! For examples of how to use the components see this example file for spatial analysis of radiant asymmetry discomfort and this example for temporal analysis.
7 - Pedestrian Wind Comfort Component Released in WIP
In preparation for the impending release of the butterfly CFD-modelling insect, Djordje Spasic with assistance from Liam Harrington has contributed a component to evaluate outdoor discomfort and pedestrian safety. The component identifies if certain areas around the building are suitable for sitting, building entrances-exits, window shopping... based on its wind microclimate. Dangerous areas due to high wind speeds are also identified.You can check it out now in the WIP section.
HONEYBEE
1 - New HVAC Systems and Full OpenStudio Support
After a significant amount of development on the part of the OpenStudio team and two years of effort on the part of LB+HB developers, we (finally!) have full support for an OpenStudio connection within Honeybee. By this, we mean that any energy simulation property that can be assigned to a HBZone will be taken into account in the simulation run by the OpenStudio component. The connection to OpenStudio has brought with it several new capabilities. Most notably, you can now assign full HVAC systems and receive energy results in units of electricity and fuel instead of simple heating and cooling loads. This Honeybee release includes 14 built-in HVAC template systems that can be assigned to the zones, each of which can be customized:
0. Ideal Air Loads 1. PTAC | Residential 2. PTHP | Residential 3. Packaged Single Zone - AC 4. Packaged Single Zone - HP 5. Packaged VAV w/ Reheat 6. Packaged VAV w/ PFP Boxes 7. VAV w/ Reheat 8. VAV w/ PFP Boxes 9. Warm Air Furnace - Gas Fired 10.Warm Air Furnace - Electric 11.Fan Coil Units + DOAS 12.Active Chilled Beams + DOAS 13.Radiant Floors + DOAS 14.VRF + DOAS
Systems 1-10 are ASHRAE Baseline systems that represent much of what has been added to building stock over the last few decades while systems 11-14 are systems that are commonly being installed today to reduce energy use. Here is an example file showing how to assign these systems in Honeybee and interpret the results and here is an example showing how to customize the HVAC system specifications to a wide variety of cases. To run the file, you will need to have OpenStudio installed and you can download and install OpenStudio from here.
In addition to these template systems within Honeybee, the OpenStudio interface includes hundreds of HVAC components to build your own custom HVAC systems. OpenStudio also has a growing number of user-contributed HVAC system templates that have been integrated into a set of scripts called "Measures" that you can apply to your OpenStudio model within the OpenStudio interface. You can find these system templates by searching for them in the building components library. Here is a good tutorial video on how to apply measures to your model within the OpenStudio interface. Honeybee includes a component that runs these measures from Grasshopper (without having to use the OpenStudio interface), which you can see a demo video of here. However, this component is currently in WIP as OpenStudio team is still tweaking the file structure of measures and it is fairly safe to estimate that, by the next stable release of Honeybee, we will have full support of OpenStudio measures within GH.
2 - Phasing Out IDF Exporter
With the connection to OpenStudio now fully established, this release marks the start of a transition away from exporting directly to EnergyPlus and the beginning of Honeybee development that capitalizes on OpenStudio’s development. As such THIS WILL BE THE LAST STABLE RELEASE THAT INCLUDES THE HONEYBEE_RUN ENERGY SIMULATION COMPONENT.
The Export to OpenStudio component currently does everything that the Run Energy Simulation component does and, as such, it is intended that all GH definitions using the Run Energy Simulation component should replace it with the OpenStudio component. You can use the same Read EP Result components to import the results from the OpenStudio component and you can also use the same Energy Sim Par/Generate EP Output components to customize the parameters of the simulation. The only effective difference between the two components is that the OpenStudio component enables the modeling of HVAC and exports the HBZones to an .osm file before converting it to an EnergyPlus .idf.
For the sake of complete clarity, we should state that OpenStudio is simply an interface for EnergyPlus and, as such, the same calculation engine is under the hood of both the Export to OpenStudio component and the Run Energy Simulation component. At present, you should get matching energy simulation results between the Run Energy Simulation component and a run of the same zones with the OpenStudio component (using an ideal air system HVAC).
All of this is to say that you should convert your GH definitions that use the Run Energy Simulation component to have the OpenStudio component and this release is the best time to do it (while the two components are supported equally). Additionally, with this version of Honeybee you will no longer need to install EnergyPlus before using Honeybee and you will only need to install OpenStudio (which includes EnergyPlus in the install).
3 - New Schedule Generation Components
Thanks to the efforts of Antonello Di Nunzio, we now have 2 new components that ease the creation of schedule-generation in Honeybee. The new components make use of the native Grasshopper “Gener Pool” component to give a set of sliders for each hour of the day. Additionally, Antonello has included an annual schedule component that contains a dictionary of all holidays of every nearly every nation (phew!). Finally, this annual schedule component can output schedules in the text format recognized by EnergyPlus, which allows them to be written directly into the IDF instead of a separate CSV file. This will significantly reduce the size of files needed to run simulations and can even reduce the number of components on your canvas that are needed to add custom schedules. For more information, see Antonello’s explanatory images here and Antonello's example file here. You can also see a full example file of how to apply the schedules to energy simulations here.
4 - EnergyPlus Lookup Folder, Re-run OSM/IDF, and Read Result Dictionary
With the new capabilities of OpenStudio, we have also added a number of components to assist with managing all of the files that you get from the simulation. In particular, Abraham Yezioro has added a Lookup EnergyPlus Folder component that functions very similarly to the Lookup Daylight Folder component. This way, you can run an Energy simulation once and explore the results separately. Furthermore, we have added components to Re-Run OpenStudio .osm files or EnergyPlus .idf files within Grasshopper. These components are particularly useful if you edit these .osm or .idf files outside of Honeybee and want to re-run them to analyze their results in Grasshopper. Lastly, a component has been added to parse the .rdd (or Result Data Dictionary) file that EnergyPlus produces, enabling you to see all of the possible outputs that you can request from a given simulation.
5 - Electric Lighting Components Out of WIP
After Sarith Subramaniam’s initial components to model electric lights with Radiance in the last release, we are happy to report that they have been fully tested and are out of WIP. Improvements include support for all types of light fixture geometries and the ability to use the components in a more “Grasshoppery” list-like fashion. See Sarith’s original release post for more information and several example files showing how to use the components can be found here. 1 , 2 , 3 .
6 - Improvements to THERM Components
A number of bug fixes and improvements have been made to the THERM components in order to make their application more flexible and smooth. Special thanks is due to Derin Yilmaz , Mel King , Farnaz , Ben (@benmo1) , and Abraham Yezioro for all of the great feedback in the process of improving these components.
7 - HBObject Transform Components
After some demand for components that can ease the generation of buildings with modular zone types, two components to transform HBObjects with all of their properties have been added to the 00 | Honeybee section. The components allow you to produce copies of zones that are translated or rotated from the original position.
8 - Comfort Maps Supports PET and Integration of CFD Results
Thanks to the addition of the ‘Physiological Equivalent Temperature’ (PET) component by Djordje Spasic in the last stable release, it is now possible to make comfort maps of PET with Honeybee. PET is particularly helpful for evaluating OUTDOOR comfort with detailed wind fields at a high spatial resolution. As such, the new PET recipe has also been optimized for integration with CFD results. The windSpeed_ input can now accept the file path to a .csv file that is organized with 8760 values in each column and a number of columns that correspond to the number of test points. Components to generate this csv from Butterfly CFD results will be coming in later releases. Stay tuned!
As always let us know your comments and suggestions.
Enjoy!Ladybug Analysis Tools Development Team
…
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as you can see I devided it into 3 parts.
part1: when I try to connect the new shape to the rest of your definition,the plan z,which gives the panels individually when baked(so I can work them individually)doesn't work,apparently there is something missing when I want to explode it.
that is why I connected it to the definition that I already had(part2)( the only cool part about that one is the attractor point)well it kind works,but not really(if you zoom in you can see that there are some parts overlapped and really not looking good).however I much rather your definition because of the option it gives me to work with individual panels when baked(planz).
however it's around 4 am. and I have decided to make some major changes in design (to prepare some closed and open space,I'm talking about part3 that works with the fibonacci like shape,I know it doesnt look really good,but seriously 4am.!).the major problem is that I tried to make a form like that with kangaroo so the shape would be smoother but I wasnt really able to make it with kangaroo,that's why I made it manually in rhino.I was wondering if you can help me make something like this ( not exacly like this) with kangaroo or (if impossible to be made with kangaroo)even helping me optimizing it so it doesnt look as bad,as you can see when I try to work the grasshopper definition on this shape,it gives me different panel sizes for each surface and all of them are to small compared with the overall size of the so-called pavillion(give it 200-500 sq feet (20-50 sq.m).and any suggestions about the shape would be appreciated,please forgive my basic knowledge of rhino and grasshopper,and let's say I wanted to make a shape like these(don't laugh please!)
u promised not to laugh!!!
please help me find the right way!
…
l coarse mesh
Subdividing this mesh into strips of thin quads
Relaxing/Planarizing this mesh
Splitting and Unrolling
In this post I deal with the first 2 of these stages.
You can download the example definition here:
developable_strips_tutorial.gh
Drawing the initial mesh
To begin with we need a simple quad mesh. This can be modelled manually in Rhino, and only needs to use enough quads to give the topology and very rough form. No need to worry too much about the exact geometry or dimensions at this point, as we will refine and alter it as we go.
One very important thing that we do need to bear in mind though is that all internal vertices must have even valence (I covered this a bit in the earlier post here).
So for example, this is bad:
(because the highlighted vertex is surrounded by 5 faces)
While this is good (and can still be relaxed to the same shape):
(the top and bottom vertices have valence 8, and the vertices between the arms have valence 4)
With a little practice it should be possible to convert any mesh into one that meets this condition.
The reasons why we need this condition should become more clear in the later steps.
First subdivision
This is where we choose how many strips we want our final model to have, by applying a few rounds of subdivision using the Refine component (you could also use Weaverbird here):
Sorting the face directions
While quad meshes do not carry the same information about u/v directions as a NURBS surface, the individual faces do have a sort of direction given by their vertex ordering. However, these face directions are usually not consistently arranged, especially after subdivision.
The Kangaroo MeshDirection component attempts* to orient all the faces in a mesh so that they match with their neighbours.
For example, before sorting, if we draw a line from the midpoint of the first edge of each face to the midpt of its opposite edge, we might get something like this:
Whereas after sorting, we should get something like this:
*note that I say it attempts to orient the faces consistently. In some cases no valid solution exists, for instance if 3 or 5 faces meet around a vertex, hence the requirement mentioned at the start for even valence vertices.
Directional Subdivision
Now that we have consistent face directions across the mesh, we can apply further subdivision, but this time in one direction only. So we go from roughly square quads to thin rectangles. The idea is that as we apply higher levels of this directional subdivision, the final relaxed result goes towards something semi-discrete. A NURBS surface is fully continuous, and a mesh is fully discrete (made up of separate facets), while this strip model will be smooth in one direction and faceted in the other.
Go to part 2 for the next step of the process
…
st shortest path. The guiding splines would work like a forcefield so that paths are "drawn" towards them with a user defined strength and radius of influence.Since each path is basically independent, it should be relatively straight forward to multithread. I downloaded the C# code for the pathfinding node and have to see if I'm up to it.
Would also be interesting to know how far away the first beta of a multithreaded GH 2 is.
I also had some hopes when "Fabric Engine" showed a demo of a Rhino exporter, since its "Canvas" is an extremely optimized node system that's fully multithreaded and optionally uses the GPU, which could be interesting to explore for some heavy lifting if they for instance would attach it to GH. But I guess it does not make much sense for them as a target.
Above image uses 20000 random points. In Softimage XSI ICE this would not be much, since it's nodes are fully multithreaded and optimized for huge numbers of particles and point deformation. In GH, with anything above 500 points, things get rather "meditative".
Illustrator takes up to half an hour after each and every change to colour, line style, blending mode etc. I have one even more complex file with over 3 GB size and there Illustrator (CS6 x64) goes into some kind of trance and after some hours of thinking moves on to some advanced psychotic, catatonic state to never fully return... ;-)So usually I run it in the background while doing something else...
I recently tried different other vector graphics apps (Inkscape, Affinity Designer, Xara) but they were even worse if they were able to open the files at all. Maybe I should give Corel a try too.
Cheers and thanks for your offer! Your work is a major inspiration for me while learning Grasshopper!
Tom…
I'v try to implement your solutions. But I found some bugs (in GH or caused by my code)
So I've create globally two params:
private IGH_Param sensRadiusParam; private IGH_Param grayScaleParam;
and some static method to create new instance of this param (example) :
private static IGH_Param addSensRadiusParam() {IGH_Param param = new Param_Number() { Name = "Sensitivity Filter Radius", NickName = "Sr", Description = "", Access = GH_ParamAccess.item }; return param; }
I'm registering three static Inputs, additional two should be optional:
And in DropDown menu I'm calling this event:
private void MenuSensitivityFilter(Object Sender, EventArgs e) { oParam.UseSensitivityFiltering = !oParam.UseSensitivityFiltering; if (oParam.UseSensitivityFiltering) { sensRadiusParam = addSensRadiusParam(); Params.RegisterInputParam(sensRadiusParam,3); } else { sensRadiusParam.RemoveAllSources(); Params.UnregisterInputParameter(sensRadiusParam, true); } this.ExpireSolution(true); }
So creation of new inputs working great. Also destroying them is fine, but rest of the behaviour is corrupted...
For example, when one of the inputs is created, I cannot connect to it any already existing on canvas object (in my case slider). If I create new object or copy existing one it works. Maybe I need to redraw canvas?
Also removing and adding Inputs in any order cause some mess on canvas... Specially when I remove connected Input.
Here, for example I've created 2 output and remove one...
As you can see, removed input param still exist somewhere... ( i can add connection between inputs slots as on picture, but when I release mouse button connection disappears, slider inheriting Input name and components get orange with warning (no data on input xxxx).. strange).
Sometimes it looks like input get connected with slider, but component warns me about "no data on input xxxxx" or slider is getting wrong name (from different parameter)
Could you help me?
I'm attaching full cs file…
ther math and logic. i can usually conceptualise what i want to do and cobble some semi working thing together but don't know which components to use and how to patch it. so i'm super happy to have someone who knows what he's doing to find this interesting.
and i'm glad you mention the fanned frets again, there is one input parameter that's still missing for the multiscale frets to be fully parametric, it's the angle of the nut or which fret should be straight. it depends a bit on personal preferences and playing posture what is more comfortable. so being able to adjust this easily would be cool. again i have no idea how the maths for that work or if you can just rotate each fret the same amount around it's middle point. The input either as fret number (for the straight fret) or as a simple slider from bridge to nut should do as input setting.
Here are the two extremes and the middle ground:
i've been thinkin today while analysing your patches and cleaning up my mess what exactly the monster should do.
Here are the input parameters needed, i think it's the complete list
scale length low E string
scale length high e string
fret angle/straight fret
string width at nut
string width at bridge
number of frets
fretboard overhang at nut (distance from string to fretboard bounds)
fretboard overhang at last fret
string gauges
string tensions
fretboard radius at nut (for compound radius fretboard radius at bridge is calculated with the stewmac formula)
fretwire crown width
fretwire crown height
action height at nut (distance between bottom of string and fretwire crown top)
action height at last fret
pickup 1 neck position
pickup 2 middle position
pickup 3 bridge position
nut width
the pickup positions should be used to draw circles for the magnet poles on each string so they are perfectly aligned and can be used for the pickup flatwork construction. ideally they would need a rotation control aligning the center line of the pickup so it's somewher between the last fret angle and bridge angle. personally i do this visually depending on the design i'm looking for, some people have huge theories on pickup positioning but personally i don't believe in it.
that should result in everything needed to quickly generate all the necessary construction curves or geometry for nut/fingerboard/frets/pickups. this is the core of what makes a guitar work, the more precise this dynamic system is the better the guitar plays and sounds.
i posted another thread trying to understand how i could use datasets form spreadsheets,databse, csv to organize the input parameters. What would make sense for the strings for example is hook into a spreadsheet with the different string sets, i attached one for the d'Addario NYXL string line which basically covers all combos that make sense.
The string tension is an interesting one, and implmenting it would sure be overkill albeit super interesting to try. it should be possible to extrapolate from the scale length of each string what the tension for a given string gauge of that string would be so that you could say 'i want a fully balanced set' or 'heavy top light bottom) and it would calculate which SKU from d'addario would best match the required tension. All the strings listed in the spreadsheet are available as single strings to buy.
i'm trying to reorganize everything which helps me understand it. i just discovered the 'hidden wires' feature which is great since once i understood what a certain block does or have finished one of my own, i can get the wires out of the way to carry on undistracted. a bit risky to hide so many wires but it makes it so much easier not to get completely lost :-)
btw, the 'fanned fret' term is trademarked, some guy tried to patent it in the 80's which is a bit silly since it has been done for centuries. there is a level of sophistication above this as well, check out http://www.truetemperament.com/ and that really is something else. it really is astounding how superior the tuning is on those wigglefrets, the problem is that it's rather awkward for string bending and also you can't easily recrown or level the frets when they are used. …
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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