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Comment on: Topic 'Discrete genome - Elite size - Display settings?'

lly it should not make much of a difference - random number generation is not affected, mutation also is not. crossover is a bit more tricky, I use Simulated Binary Crossover (SBX-20) which was introduced already in 1194:Deb K., Agrawal R. B.: Simulated Binary Crossover for Continuous Search Space, inIITK/ME/SMD-94027, Convenor, Technical Reports, Indian Institue of Technology, Kanpur, India,November 1994Abst ract. The success of binary-coded gene t ic algorithms (GA s) inproblems having discrete sear ch sp ace largely depends on the codingused to represent the prob lem variables and on the crossover ope ratorthat propagates buildin g blocks from pare nt strings to childrenst rings . In solving optimization problems having continuous searchspace, binary-co ded GAs discr et ize the search space by using a codingof the problem var iables in binary st rings. However , t he coding of realvaluedvari ables in finit e-length st rings causes a number of difficulties:inability to achieve arbit rary pr ecision in the obtained solution , fixedmapping of problem var iab les, inh eren t Hamming cliff problem associatedwit h binary coding, and processing of Holland 's schemata incont inuous search space. Although a number of real-coded GAs aredevelop ed to solve optimization problems having a cont inuous searchspace, the search powers of these crossover operators are not adequate .In t his paper , t he search power of a crossover operator is defined int erms of the probability of creating an arbitrary child solut ion froma given pair of parent solutions . Motivated by t he success of binarycodedGAs in discret e search space problems , we develop a real-codedcrossover (which we call the simulated binar y crossover , or SBX) operatorwhose search power is similar to that of the single-point crossoverused in binary-coded GAs . Simulation results on a number of realvaluedt est problems of varying difficulty and dimensionality suggestt hat the real-cod ed GAs with t he SBX operator ar e ab le to perform asgood or bet t er than binary-cod ed GAs wit h t he single-po int crossover.SBX is found to be particularly useful in problems having mult ip le optimalsolutions with a narrow global basin an d in prob lems where thelower and upper bo unds of the global optimum are not known a priori.Further , a simulation on a two-var iable blocked function showsthat the real-coded GA with SBX work s as suggested by Goldbergand in most cases t he performance of real-coded GA with SBX is similarto that of binary GAs with a single-point crossover. Based onth ese encouraging results, this paper suggests a number of extensionsto the present study.7. ConclusionsIn this paper, a real-coded crossover operator has been develop ed bas ed ont he search characte rist ics of a single-point crossover used in binary -codedGAs. In ord er to define the search power of a crossover operator, a spreadfactor has been introduced as the ratio of the absolute differences of thechildren points to that of the parent points. Thereaft er , the probabilityof creat ing a child point for two given parent points has been derived forthe single-point crossover. Motivat ed by the success of binary-coded GAsin problems wit h discrete sear ch space, a simul ated bin ary crossover (SBX)operator has been develop ed to solve problems having cont inuous searchspace. The SBX operator has search power similar to that of the single-po intcrossover.On a number of t est fun ctions, including De Jong's five te st fun ct ions, ithas been found that real-coded GAs with the SBX operator can overcome anumb er of difficult ies inherent with binary-coded GAs in solving cont inuoussearch space problems-Hamming cliff problem, arbitrary pr ecision problem,and fixed mapped coding problem. In the comparison of real-coded GAs wit ha SBX operator and binary-coded GAs with a single-point crossover ope rat or ,it has been observed that the performance of the former is better than thelatt er on continuous functions and the performance of the former is similarto the lat ter in solving discret e and difficult functions. In comparison withanother real-coded crossover operator (i.e. , BLX-0 .5) suggested elsewhere ,SBX performs better in difficult test functions. It has also been observedthat SBX is particularly useful in problems where the bounds of the optimumpoint is not known a priori and wher e there are multi ple optima, of whichone is global.Real-coded GAs wit h t he SBX op erator have also been tried in solvinga two-variab le blocked function (the concept of blocked fun ctions was introducedin [10]). Blocked fun ct ions are difficult for real-coded GAs , becauselocal optimal points block t he progress of search to continue towards t heglobal optimal point . The simulat ion results on t he two-var iable blockedfunction have shown that in most occasions , the sea rch proceeds the way aspr edicted in [10]. Most importantly, it has been observed that the real-codedGAs wit h SBX work similar to that of t he binary-coded GAs wit h single-pointcrossover in overcoming t he barrier of the local peaks and converging to t heglobal bas in. However , it is premature to conclude whether real-coded GAswit h SBX op erator can overcome t he local barriers in higher-dimensionalblocked fun ct ions.These results are encour aging and suggest avenues for further research.Because the SBX ope rat or uses a probability distribut ion for choosing a childpo int , the real-coded GAs wit h SBX are one st ep ahead of the binary-codedGAs in te rms of ach ieving a convergence proof for GAs. With a direct probabilist ic relationship between children and parent points used in t his paper,cues from t he clas sical stochast ic optimization methods can be borrowed toachieve a convergence proof of GAs , or a much closer tie between the classicaloptimization methods and GAs is on t he horizon.In short, according to the authors my SBX operator using real gene values is as good as older ones specially designed for discrete searches, and better in continuous searches. SBX as far as i know meanwhile is a standard general crossover operator.But:- there might be better ones out there i just havent seen yet. please tell me.- besides tournament selection and mutation, crossover is just one part of the breeding pipeline. also there is the elite management for MOEA which is AT LEAST as important as the breeding itself.- depending on the problem, there are almost always better specific ways of how to code the mutation and the crossover operators. but octopus is meant to keep it general for the moment - maybe there's a way for an interface to code those things yourself..!?2) elite size = SPEA-2 archive size, yes. the rate depends on your convergence behaviour i would say. i usually start off with at least half the size of the population, but mostly the same size (as it is hard-coded in the new version, i just realize) is big enough.4) the non-dominated front is always put into the archive first. if the archive size is exceeded, the least important individual (the significant strategy in SPEA-2) are truncated one by one until the size is reached. if it is smaller, the fittest dominated individuals are put into the elite. the latter happens in the beginning of the run, when the front wasn't discovered well yet.3) yes it is. this is a custom implementation i figured out myself. however i'm close to have the HypE algorithm working in the new version, which natively has got the possibility to articulate perference relations on sets of solutions.…

Added by Robert Vier to Octopus at 1:59pm on June 8, 2013

Comment on: Topic 'Beyond BIM: transitioning from 3D Generative/Parametric design to the industry…'

h have significant business consequences so that is still something that should be carefully considered.In the software realm, I think your correct in that the "BIM" products that are available are more archaic then their "groundbreaking" image will lead you to believe. IMHO these products don't have the capability to really create the proper geometry for a direct model to manufacturing type of situation that is evident in other industries. Also, these products are geared towards creating standard architect where a wall is a wall, a window's a window and a door's a door. Generally, once you step out of that fairly restrictive box, you're left completely up a creek without a paddle in sight. Needless to say, your answer most likely does not lie within those packages. GC may be able to help make microstation a bit more flexible, but I'm really not sure to what extent that will actually satisfy your needs.The other end of the spectrum is CATIA/DP, and although it is immensely capable, there are a whole lot of other considerations that need to be made. Geometry wise, you will be able to create, control, and manage all of your design exactly how you need to. CATIA is used to build cars and aircraft down to the last nut and bolt (threads and all), so you have all the capabilites that you'll need to do the work that your looking to do. Not only that, but there are ample drafting capabilities within CATIA, so the short term goal of needing 2D drawings won't be left on the wayside (I doubt it ever really will). The problems that go along with this are costs, time, and implications up and down stream. CATIA/DP is very expensive, not only in the cost of the product, but also in training, and you WILL need training. If you're disappointed about what's available from Bentley, then realize that you'll be getting even less from Dassault. GT really is more of a consulting firm at the moment in that a large amount of what they do is actually work with firms to have them use DP. That to me points to it being a hard platform to really have a whole office working with efficiently, but that's more speculation than anything else in this response. The other issue is that CATIA take a lot of time to use. The parametric aspect means that there's a lot to setup, and if that setup isn't exactly what's needed, then you may have to go back and rebuild parts of the model. This is somewhat diminished with experience, but its always there. The other thing is that outside of generating 2D drawings from the model, it may be harder to transfer that model towards other parties (ie contractors/engineers). Some may have the capability to take a CATIA model or an IGES model or something, but others may not. Since a lot about the modeling to manufacturing process isn't really standardized within the AEC industry, there also isn't much in regards to guidance out there.The other thing to consider here (which you briefly touched upon) is the use of analysis programs on your design. That's a whole other set of issues, and one that you should consider as that will likely become a more important aspect of the design process as the profession progresses.Your professional questions really seam to center around using a model for manufacturing purposes. At this point, this really only done on smaller aspects of a project as opposed to the whole thing. Also, most firms who are doing a lot of complicated fabrication have people who are familiar enough with the fabrication process to understand how models need to be constructed in order to be manufactured. Modeling for manufacturing has more requirements than just modeling for drawing generation or visualization purposes, so its important to understand those requirements. Working with a fabricator can help make sure that you get them what they need, but getting the model right is an additional requirement of the process. The other side of the model to manufacturing process is having the manufacturers, and in architecture's case, the contractors, on board with this and be willing to completely shift their typical way of working. Some contractors (generally the larger ones) have already started to integrate a "drawingless" process, but as I understand it, its not 100% of the way there. Moving towards this generally involves a lot of risk that the architects need to take, and in a profession where we're told from the top down to minimize or avert risk, this is a significant aspect of taking on this process. Personally, I think that taking responsibility for risk also gives you the opportunity to control it, so if you can properly control it, the end result can be positive. How you feel about risk will dictate what your comfortable with taking on.I could continue, but I think that I've covered enough for one post.…

Added by Damien Alomar at 11:59am on March 22, 2010

Comment on: Topic 'Refactoring Parametricism'

bi-directional link, the link is unidirectional (downflow only), because of the use of proxies.Matrix transforms and persistent constraints: I don't think this is true. The parts can have mates to other parts that preserve geometric relationships like 'coincident' , 'aligned' etc. These are essentially bi-directional. GH's algorithmic approach does not do relationships in the same / flexible way. In GH, the 'relationship' has to be part of the generation method that dependent on the creation sequence. I.e. draw line 2 perpendicularly from the end of point of line 1. If you are thinking about parts or assemblies sharing, or referencing parameters as part of the regen process, this is also possible. iLogic does this, and adds scripting. So does Catia. Inventor/iLogic can also access Excel and have all the parameter processing done centrally, if required.Consequently, scripting the placement of components is irrelevant in GH, unless you decide that each component needs to be contained in its own separate file.I wouldn't be too hasty here. Yes, you are right about compartmentalisation. I think this needs to happen with GH, in order to deal with scalability/everyday interoperability requirements. Confining projects to one script is not sustainable. MCAD apps have been doing this for ages with 'Relational Modeling'.The Adaptive Components placement example illustrates that it is beneficial to be able to script some 'hints' that can be used on placement of the component. Say, if your component requires points as inputs, then its should be able to find the nearest points to the cursor as it moves around. I think Aish's D# / DesignScript demo'd this kind of behaviour a few years ago. Similarly, Modo Toolpipe reminds me how a lot of UI based transactions can be captured as scripts (macro recorder etc). Allowing this input to be mixed in and/or extended by GH I think will yield a lot of 'modeling efficiency' around the edges. This is a (mis)using GH as an user-programmable 'jig' for placing/manipulating 'dumb' elements in Rhino. It may even give the 'dumb elements' a bit more 'intelligence' by leaving behind embedded attributes, like links to particular construction planes etc.Even if we confine ourselves to scripting. GH is a visual or graphic programming interface. A lot of 'insert and connect' tasks can be done more easily using graphic methods. If we need to select certain vertices on a mesh as inputs for, say, a facade panel, its going to be quicker to do this 'graphically' (like the AC example), then ferreting out the relevant indices in the data tree et al. The 'facade panel' script would then have some coding to filter/prompt the user as to what inputs were acceptable, and so on.This also brings up the point that generating components and assemblies in MCAD is not as straightforward. In iParts and iAssemblies, each configuration needs to be generated as a "child" (the individual file needs to be created for each child) before those children can be used elsewhere.Not sure what you mean here. If the i-parts are built up using sketches /profiles or other more rudimentary features (like Revits' profile/face etc family templates) then reuse should be fairly straight forward. I suppose you could make it like GH scripting, if you cut and paste or include script snippets that generate the desired Inventor features.One of the reasons why the distributed file approach makes perfect sense in MCAD, is that in industry you deal with a finite set of objects. Generative tools are usually not a requirement. Most mechanical engineers, product engineers and machinists would never have any use for that.I don't think this is true. Look at the automotive body design apps, which are mostly Catia based. All of the body parts are pretty much 'generative' and generated from splines, in a procedural way, using very similar approaches to GH. Or sheet metal design. It's not always about configuration of off-the-shelf items like bolts. And, the constraints manager is available to arbitrate which bit of script fires first, and your mundane workaday associative dimensions etc can update without getting run over by the DAG(s) :-)…

Added by dominic at 12:51pm on February 26, 2011

Comment on: Topic 'C# Access sliders question'

- nickname is rather the best approach - and not on active group, but that's irrelevant anyway).Step back (assuming that you are talking about the "Tens_from_random_blah_blah" definition):1. Engineering is the art of demystifying (or we are promising that anyway, he he). This means that you start defining (better: outlining) some topology for things based on some "generic" rules (like the ones applied for the masts,cables,cones etc etc). These things are kept in some kind of structure (Lists, DataTrees etc). Things are few in 99.99999% of cases (i.e. : even the biggest membrane "module" has, say, 20-50 masts per "module").2. Then ... handling things "individually" (mostly modifying) becomes the most critical part. See this (an x "possible" solution by combining a myriad of "options" : a no cones membrane solution, in plain English): 3. But the above is impossible (for more than obvious reasons). You should deploy masts in some high/low sequence in order to achieve some meaningful convex/concave formation that could work.4. This "works" : 5. This doesn't:6. This works partially (the formation at the back is "flat" == undo able):7. This is utterly kitsch (and faulty as the case6 - the back portion):So it's quite obvious that without a (quite complex) capability to individually control things (in this occasion : mast heights) the whole definition is a waste of computer time. Additionally the more the solution is "demystified" (some curve is defined, some random points are created, some masts are in place, some cables appear etc etc) the more additional constrains are required in order to "narrow" the possibilities (In plain English : sliders should control other sliders as regards their min/max values, true/false, you/me etc etc).Remember that we are talking about ONE (mast height) out of a myriad things that you should control "manually" (it's utterly pointless to mastermind some kind of "generic" rules - or use naive attractors etc etc) .You'll see the difference when I'll completely reform the definition by adding individual control upon anything.PS: what about the blocks? (the real life stuff that actually make any solution possible). Can you imagine a 2nd set of "restrictions" imposed by "a child to his parent"? (Assembly/Component modeling , that is).more soon…

Added by peter fotiadis at 12:38am on November 18, 2014

Topic: Sine graph reversal on curve [updated]

ay to use a sine wave length along a curve with the grasshopper script below. [Update: done, thank you TOM].I am trying to figure out a way to reverse the sine wavelength.Current problems:1.)Reversing the sine wavelength along the curve. And provide a graph to allow for different graphs. I.e., I want to have a sine wavelength on the base, and 3200mm above a wavelength of a different sort. Current File: (apply curve to any curve)Brick%20problem.gh 2.) Contouring when lofted to allow for HFrame placementI need to be able to apply the script to curves; and be able to adjust a series of points, and the multipiers to adjust the width the curve extrudes in the y axis away from the curve at a perpendicular angle.Current: (took a long time but this is where I am now)OLD:Fixing: Achieved: Also, is there a way to do this without series and by linking surfaces already in Rhino3d?Sine wavelength below, and intention to use the brick wall on in picture after.I've been following Nick Senske's work on YouTube for those wondering.I hope to achieve something similar to the pictures attached:http://www.zja.nl/image/2014/10/15/2112_500_325.jpg(mediaclass-default.f996b08cf5abfa43b3b03133a89ec231272756a9).jpghttp://www.zja.nl/en/page/2311/parametric-design-for-brick-surfacesEdits: Removal of unneeded content and grammar. Update of pictures and progress. Thanks to Tom for his assistance.…

Added by Iain McQuin at 9:52pm on October 18, 2016

Comment on: Topic 'Baking Breps w/ Color - RHINOCOMMON'

es only have one raison d'être, which is to group types into logical chunks.A Type is the definition of a class or a structure. Classes and structures are very similar entities (they can both contain any number of methods, properties and other types), but because they behave differently, you need to know which is which.An Instance of a type is a single object that actually exists. For example, the class Human is the definition of what it means to be human. You are an instance of this class. I am a different instance of this class. Damien is yet another instance of this class. Every instance can assign unique values to all its properties and fields. If for example the type Human had a property for height, then in my case it would say 1.97m. In Damien's case it would be set to something much less, as Damien isn't anywhere near as handsome and tall as I am.A Reference is a piece of information that tells you where a certain instance is. Think of a reference as an address. When you mail a letter (or e-mail), you must specify a valid and unambiguous address or the letter won't arrive. Similarly, every piece of data stored in the memory of your computer also has a unique address, but instead of "3670, Woodland Park Avenue, Seattle", it looks like this 0x12345678. Trying to access an instance through an invalid reference is like sending a letter without an address.References are sometimes also called "variables", though sometimes the word variable is only used to indicate primitive types, such as Booleans, Integers and such. A reference is not the instance itself. Take the following code:1. Dim crv As Rhino.Geometry.Curve2. Dim dup As Rhino.Geometry.Curve3. crv = GetACurveFromSomewhere()4. dup = crv5. If (dup IsNot Nothing) Then dup = dup.DuplicateCurve()One lines (1) and (2) I declare two references, one is called "crv", the other "dup". Because Visual Basic is a strongly typed language, I can assign limitations to what sort of data crv and dup are allowed to reference. In this case they can only point to instances of the Rhino.Geometry.Curve classor any class which derives from Rhino.Geometry.Curve (such as Rhino.Geometry.NurbsCurve, or Rhino.Geometry.LineCurve).On line (3) I assign an actual curve instance to the crv reference/variable. At least, assuming the GetACurveFromSomewhere() function actually returns a proper instance. If it doesn't, crv will remain a "null reference".Line (4) is interesting, because both crv and dup will now point to the same curve instance. So even though there is only 1 curve in memory, both crv and dup provide access to it. This means that when we change the curve via crv, then dup will notice that change.On line (5) two things happen. I want to duplicate my curve data so I can change the data via dup, without affecting the data available via crv. The best way to duplicate a curve (i.e. create a second curve in memory, that has the same shape as the first curve) is to use the DuplicateCurve() method on the Rhino.Geometry.Curve class. However I cannot call a method on an instance that doesn't exist, so before I do that, I need to check whether or not dup actually points to a real curve object, or whether it is a null reference.Finally, it is also possible to have an instance of a class in memory, without any references to it. In this case nobody can reach that curve any more and it is essentially dead weight, taking up pointless memory. In C++ this is called a Memory Leak and it's considered a serious bug. In VB.NET and C# this memory will automatically be cleaned up by the .NET Garbage Collector. In my opinion the Garbage Collector is the single most important feature in .NET. It's what turns VB and C# from frustration central into a friendly and flexible coding platform.--David Ruttendavid@mcneel.comPoprad, Slovakia…

Added by David Rutten at 4:10pm on August 9, 2011

Comment on: Topic 'Towards HB Agent Based Models?'

is lately. I believe you are absolutely right to say that the type of behavior to be modelled will define if we actually need an ABM interface. If, as you say, the parameters modelled are temperature or radiation, then I imagine that a lot of studies can be done within E+, perhaps in the stepwise way you described earlier.Additionally, and this is my main critic on ABM in general but I'll leave it for another discussion, the degree of freedom or interaction with the environment that an agent has dictates the possibilities for an ABM. In typical models this has to do with how you model innovation in agents, changes in their practices and norms (which generally isn't there in ABM models). In our case, it related to the type of environments our agents are situated in.I can imagine two extreme cases of environments, with ofc a gradient of possible worlds between: the mechanically conditioned building and the naturally ventillated building.In the first case, which btw is the one most encountered in my part of the world, the agents have minimal, to sometimes zero, control on their environment and no capabilities of adaptation and change. Imagine a typical building where the set points are set centrally, windows are not operable, and even the shading devices are sometimes out of their reach.In this case, I can imagine ABM models helping only as a post processing tool. What that means is that we could potentially use them to analyze occupant behavior within this controlled environment. E+ would give us the hourly space performance and we would feed that to agents to see how they respond. Ofc, in terms of thermal comfort this is almost what your tools are doing. So, such an approach would have little value in an office building for example where people are assumed static but could be interesting in retail buildings where we could potentially model occupant movement according to building performance. The limits of this approach then is some sort of scenario testing of different settings and occupant (response) behavior to them. Here of course, you have a valid point of other building characteristics that should be modelled, apart from climate.In the second case, that of an adaptive building, I believe ABM can be a tool that can be used in a co-simulation approach, as it has been used in the site Mostapha mentioned above. Again though, in ABM it is critical to not overdefine behavior but on the contrary to generate behavior from assigning simple rules to agents. This makes it difficult for me to find the limit of detail in the functions/statistics used to model occupant actions within the building (on windows, shading, thermostats, etc.).Since ABM is better fitted to generate patterns that we encounter in the real world, I thought of developing a model that might do exactly that. It took me a while to think of a pattern that would be interesting, but I think I finally have it. It is a bit of a grand gesture of course, but should be worth it.As you know better than me from your research, the adaptive comfort studies found a quite peculiar fact about the tropics. The sentence went something like this (I'm botching it probably), "people in the tropics tend to prefer environments that are below the limits of their neutral comfort". Or simpler, people just want to the space to be colder than what one calls neutral.My simple minded explanation, after leaving in the region, is that the explanation for this is to be found in the interface between outside and inside. The temperature gradient in that interface is what makes people feel more comfortable in uncomfortable (i.e. colder) conditions.So what if we would introduce a shaded, open, naturally ventilated space prior to a MV building's entrance and then increase your indoor temperatures in the building? Or what if we introduced a temperature gradient in the different spaces a visitor/occupant passes through as he enters the building. I feel that energy modelling cannot really understand the impact of these interventions on occupants, at least in its basic form. I think this is where ABM could be useful. Building a model that can generate the above mentioned pattern and then using it to analyze different types of strategies to occupant behavior.I wanted to write the things above in a more structured way but I forgot my cheat-sheet at home :) I hope I made some sense.I will try and be patient and follow the route you suggest however, understanding the E+ resources first and then moving to connecting it to ABM.I just thought I'd describe the sort of research questions I have in mind for this, hoping someone finds it interesting as well!Kind regards,Theodore.P.S.: I have left out other areas that would be suitable for ABM modeling within buildings. For example the area of health and safety. ABM is an amazing tool to model occupant behavior in extreme events, e.g. fire in a building or toxic smoke, etc. in order to analyze evacuation patterns and optimize building design. Even though this is something I am also interested, I intentionally did not go into it since we are mostly dealing with environmental design here.…

Added by Theodoros Galanos to Ladybug Tools at 7:47pm on January 3, 2016

Topic: Karamba Modal Analysis

ponse Factor (dynamic serviceability criteria) for structures such as office floors which are often governed by dynamic considerations and sensitivity to accelerations. This response factor calculation node is then used in an optimisation loop (Hoopsnake) along with a Eurocode section sizing node to determine required sections from a standard database for a given geometry, support, and loading condition. We have done some work with the new version of Karamba and have a few questions regarding the eigenvectors and the normalisation thereof. You have mentioned that the eigenvectors in Karamba are scaled to unity with respect to the mass matrix. In other words the eigenvectors form a mass orthonormal set, i.e. for mode r, the modal mass = [eigenvectorr]T . [mass matrix] . [eigenvectorr] = 1.As you also mentioned, this implies that the length of each mode’s eigenvector = 1/Sqrt(m*) where m* is the modal mass in that mode. We have taken your modal analysis example and re-analysed it in Autodesk Robot to compare results. I have used a consistent mass matrix to calculate the results (I assume Karamba has used a lumped mass matrix for computational efficiency?). The results (frequencies, mass-normalised eigenvectors, modal masses, and mass participation factors) of this analysis are shown below:mX,mY,mZ are the modal masses of the current mode calculated assuming unity-normalised eigenvectors (if they were calculated with mass-normalised eigenvectors, all of the modal masses would of necessity be 1).miX,miY,miZ are the nodal modal masses (∑miX=mX)Cur.mas.Ux gives the mass participation (%) of the current mode.Modal mass and participation coefficients are calculated in Robot as described in this link. Dynamic analysis methods used by Robot are presented here– I used the subspace iteration method for the results above (but all methods give almost identical results as long as enough modes are calculated). The above analysis shows a modal mass mY=40.5 kg (½ of the total mass) for the first mode. This result satisfies the basic theory: for mode n of a uniform simply-supported beam of span L and mass/unit length m, the (unity-normalised) mode shape is given by ɸ = sin (nπx/L), and the modal mass M* = m*Integral(Sin2(nπx/L),dx,[0,L]) = 0.5*m*L. In discrete form this is M* = ∑Mi*ɸi. I attach a slight modification to your modal analysis example where I have attempted to back-calculate the modal mass from the length of the eigenvectors output for each mode. This seems to return low modal masses less than 1 – I was expecting them to be one (as the Karamba eigenvectors I am back-calculating from are mass-normalised). Would you be able to shed some light on this?I also attempted to calculate the eigenvectors and modal masses in Karamba for the same 10m long beam, but with a 1000kg point mass at the centre of the beam, so I could compare the simpler three modes of that nodal mass with Robot. However I could not set the density of the beam to zero hence could not get pure modal results for the point mass. Should this be possible? We also had a couple of requests (some already mentioned by email):Is it possible to expose the eigenvectors as actual vectors at a requested number of divisions along each bar, similar to the section forces?Is it possible to allow us to specify to Karamba which directions the mass is activated in? For example, for a floor structure you are often only concerned with the modes activating mass in a vertical direction, as one is aware that a composite topping will restrain the beams laterally and torsionally. This would not need to take the form of an additional node, but simply X-Y-Z radio boxes similar to the supports component. This could either be an implementation of a solution to the reduced dynamics problem in the selected direction, or simply cull out all modes which had mass participating in directions not selected (using for example the participation factors described below). The first option would be more technically accurate, as most structural systems are coupled.I understand modal masses can be scaled arbitrarily and do not necessarily have any direct relationship to the real structure mass (they can be scaled). However one particular scaling of them is useful, often known as the ‘effective modal mass’. This is the set of modal masses which add up to the total mass and are directly related to the Modal Participation Factors (see e.g. Clough & Penzien pg. 308 or the link below). Can these factors for each mode be calculated as well in Karamba? This is useful for determining how ‘important’ each mode is and how they contribute to the dynamic response of the structure. This linkdescribes well the calculation of effective modal masses and the modal participation factor.Thanks again for Karamba - it is an extremely useful tool!Kind regards,Luke…

Added by Lucas Epp to Karamba3D at 5:07pm on January 21, 2012

Topic: Python in Grasshopper: Mapping Buildings onto grasshopper built topography #urgent

o my python component returning null despite running fine in the standalone python editor (i.e.: not through grasshopper).The original python script is as follows:import randomimport rhinoscriptsyntax as rsrs.EnableRedraw(False)def placeBuildings(curve, distance): pts=rs.DivideCurveLength(curve,5) counter=0 for myPoint in pts: counter=counter+1 #get the parmeter f current positision param=rs.CurveClosestPoint(curve,myPoint) #get teh tangent of this parameter tangent=rs.CurveTangent(curve,param) #calculate the angle of the tangent angle=rs.Angle((0,0,0),tangent) randomNumber=random.uniform(1,5) heightOfBuilding=random.uniform(4,40) rect=rs.AddRectangle(rs.WorldXYPlane(),randomNumber,2) rs.MoveObject(rect,(0,randomNumber,0)) hull=rs.ExtrudeCurveStraight(rect,(0,0,0),(0,0,heightOfBuilding)) rs.RotateObject(hull,(0,0,0),angle[0]) rs.MoveObject(hull,myPoint) #if counter%4: #rs.AddCircle(myPoint,3) #selection of curve#curveParameter=rs.GetCurveObject("sel curve")#curve=curveParameter[0]curves=rs.GetCurveObject("select streets",4)distance=rs.GetInteger("distance?",4)for curve in curves: placeBuildings(curve,distance) rs.ReverseCurve(curve) placeBuildings(curve,distance)When placed in grasshopper it is the following:import randomimport rhinoscriptsyntax as rs#randomNumber=random.uniform(1,5)#rs.AddCircle((0,randomNumber,0), 2)def placeBuildings(curve, distance): pts=rs.DivideCurveLength(curve, 5) counter=0 for myPoint in pts: counter=counter+1 #get the parmeter f current positision param=rs.CurveClosestPoint(curve,myPoint) #get teh tangent of this parameter tangent=rs.CurveTangent(curve,param) #calculate the angle of the tangent angle=rs.Angle((0,0,0),tangent) randomNumber=random.uniform(1,5) heightOfBuilding=random.uniform(4,40) rect=rs.AddRectangle(rs.WorldXYPlane(),randomNumber,2) rs.MoveObject(rect,(0,randomNumber,0)) hull=rs.ExtrudeCurveStraight(rect,(0,0,0),(0,0,heightOfBuilding)) rs.RotateObject(hull,(0,0,0),angle[0]) rs.MoveObject(hull,myPoint)#selection of curve#curveParameter=rs.GetCurveObject("sel curve")#curve=curveParameter[0]curves=xdistance=yfor curve in curves: placeBuildings(curve,distance) rs.ReverseCurve(curve) placeBuildings(curve,distance)I am unsure why there is no error being returned yet I cannot achieve any result other thannull.Maybe someone could look at the script and tell me what is going wrong? I'm hoping to solve this before next Thursday so I might be asking for too much.Much Appreciated.-A…

Added by Adem O'Byrne at 11:45am on October 9, 2014

Blog Post: new book AAD Algorithms-Aided Design | Parametric Strategies using Grasshopper by Arturo Tedeschi

AAD_Algorithms-Aided Design …

Added by Arturo Tedeschi at 7:57am on October 8, 2014

Scott Davidson created this Ning Network.