t, let's talk about randomness. Randomness is a problem in computing because digital computers are deterministic. If you give them the exact same instructions they always end up with the exact same result. It turns out to be mathematically impossible to generate true random numbers using a digital computer, but it is fairly easy to generate pseudo-random numbers. This is actually not bad news as pseudo-random numbers -unlike real random numbers- can be generated again and again and you'll end up with the same random numbers every time. Being able to get the same random numbers on demand increases the reliability of these number sequences which in turn makes them easier to use.
Pseudo-random numbers are numbers that have certain characteristics. Note that when we talk about random numbers we are really talking about numbers. Plural. It's easy to generate only a single one, as xkcd so eloquently put it:
So what are these characteristics that define pseudo-randomness? Without being actually correct, I can sum them up as follows:
The sequence of generated numbers should never repeat itself*
The numbers in the sequence ought to be spread evenly across the numeric domain**
There are a lot of different algorithms out there, some better than others, some faster than others, some solving very specific problems while others are more generic. The generator used in Grasshopper is the standard Microsoft .NET Random, based on Donald Knuth's subtractive algorithm.
So let's imagine we want random integers between 0 and 10. What would a bad random sequence look like?
3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 (about as bad as it gets)
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 (not random at all)
1 3 2 5 3 9 1 2 4 2 5 1 1 2 8 1 5 2 3 4 (too many low numbers)
2 8 4 6 0 9 8 2 4 8 6 4 2 2 5 1 4 8 6 2 (too many even numbers)
So what about good sequences? Well, here's a few:
6 9 1 2 0 4 2 8 5 7 2 9 1 9 2 5 3 1 9 2 (sure, why not)
6 2 5 3 4 1 9 7 8 0 2 1 6 4 5 8 9 5 0 9 (looks about right)
1 8 5 2 3 4 5 7 9 5 2 1 0 2 1 0 9 7 6 4 (I suppose)
9 0 6 4 8 3 1 5 2 7 6 1 4 6 0 1 9 7 5 6 (whatever)
There are a lot of valid pseudo-random sequences. (Seriously, loads). So even if we have a good pseudo-random generator we may be given a random sequence that isn't entirely to our liking. The shorter the sequence we need, the more likely it is that statistical aberrations invalidate that particular sequence for us. What we need is some control over the generator so we don't just get a repeatable sequence, but a repeatable sequence we actually like.
Enter seed values. The random generator requires a seed value before it can generate a random sequence. These seed values are always integers, and they can be any valid 32-bit integer. Every unique seed value results in the same sequence. Every time.
Unfortunately there is no clear relationship between seeds and sequences. Changing the seed value from 5 to 6 will result in a completely difference random sequence, and two sequences that are very similar may well have to wildly different seeds. There is therefore no way to guess a good seed value, it is completely trial-and-error. Also because of this extremely discontinuous nature, you cannot use tools like Galapagos to optimize a seed value.
If you are looking for a pseudo-random sequence which has custom characteristics, you may well end up having to write your own generator algorithm. Ask questions about this on the Grasshopper main forum or the VB/C# forum.
Conclusion: Seed values are integers that define the exact sequence of pseudo-random numbers, but there's no way of knowing ahead of time what sequence it will be and there's no way of tweaking a sequence by slightly changing the seed. Even the tiniest change in seed value will result in a radically different random sequence.
--
David Rutten
david@mcneel.com
Poprad, Slovakia
* This is not actually possible. A finite amount of numbers always repeats itself eventually.
** This should only be true for long enough sequences, short sequences are allowed to cluster their values somewhat.
Interesting links for further reading:
Coding Horror: Computers are Louse Random Number Generators
StackOverflow: When do random numbers start repeating?…
Added by David Rutten at 9:52am on October 20, 2012
will work slightly different from before. Sorry about breaking this, but it proved impossible to improve the selection logic with the fairly ambiguous notation that was implemented already.
Not every change is breaking though and I hope that most simple matching rules will work as before. There will be a McNeel webinar on Wednesday the 6th of November where I discuss the new selection rules (as well as path mapping syntax and relative offsets within one or more data trees). This will be a pretty hard-core webinar aimed at expert users. The event will be recorded so you can always go and watch it later. I figured I'd briefly explain the new selection rules on Ning before I release the update though.
-------------------------------------------------------------------------------
Imagine we have the following data tree, containing a bunch of textual characters:
{0;0} = [a,e,i,o,u,y] {0;1} = [ä,ë,ê,ï,î,ö,ô,õ,ü,û,ÿ,ý] {1;0} = [b,c,d,f,g,h,j,k,l,m,n,p,q,r,s,t,v,w,x,z] {1;1} = [ç,ĉ,č,ĝ,ř,š,ş,ž]
There are a total of four branches {0;0}, {0;1}, {1;0} and {1;1}. The first branch contains all the vowels that are part of the standard English alphabet. The second branch contains all non-standard vowels and branches three and four contain the standard and non-standard consonants respectively.
So what if we want to select from this tree only the standard vowels? Basically include everything in the first branch and disregard everything else. We can use the [Tree Split] component with a selection rule to achieve this:
{0;0}
This selection rule hard-codes the number zero in both tree path locations. It doesn't define an item index rule, so all items in {0;0} will be selected.
If we want all the vowels (both standard and non-standard), then we have several options:
{0;?} = select all branches that start with 0
{0;(0,1)} = select all branches that start with 0 and end in either 0 or 1
{0;(0 to 1)} = ......................................... and end in the range 0 to 1.
Conversely, selecting all standard vowels and consonants while disregarding all non-standard character can be achieved with rules as follows:
{?;0}
{(0,1);0}
{(0 to 1);0}
It is also possible to select items from each branch in addition to limiting the selection to specific branches. In this case another rule stated in square brackets needs to be appended:
{0;?}[0 to 2]
The above rule will select the first three vowels from the standard and the non-standard lists.
Basically, rules work in a very consistent way, but there are some syntax conventions you need to know. The first thing to realize is that every individual piece of data in a data-tree can be uniquely and unambiguously identified by a collection of integers. One integer describes its index within the branch and the others are used to identify the branch within the tree. As a result a rule for selection items always looks the same:
{A;B;C;...;Z}[i] where A, B, C, Z and i represent rules.
It's very similar to the Path Mapper syntax except it uses square brackets instead of parenthesis for the index (the Path Mapper will follow suit soon, but that won't be a breaking change). You always have to define the path selector rule in between curly brackets. You can supply any number of rules as long as you separate them with semi-colons.
The index rule is optional, but -when provided- it has to be encased in square brackets after the path selection rule(s).
The following rule notations are allowed:
* Any number of integers in a path
? Any single integer
6 Any specific integer
!6 Anything except a specific integer
(2,6,7) Any one of the specific integers in this group.
!(2,6,7) Anything except one of the integers in this group.
(2 to 20) Any integer in this range (including both 2 and 20).
!(2 to 20) Any integer outside this range.
(0,2,...) Any integer part of this infinite sequence. Sequences have to be at least two integers long, and every subsequent integer has to be bigger than the previous one (sorry, that may be a temporary limitation, don't know yet).
(0,2,...,48) Any integer part of this finite sequence. You can optionally provide a single sequence limit after the three dots.
!(3,5,...) Any integer not part of this infinite sequence. The sequence doesn't extend to the left, only towards the right. So this rule would select the numbers 0, 1, 2, 4, 6, 8, 10, 12 and all remaining even numbers.
!(7,10,21,...,425) Any integer not part of this finite sequence.
Furthermore, it is possible to combine two or more rules using the boolean and/or operators. If you want to select the first five items in every list of a datatree and also the items 7, 12 and 42, then the selection rule would look as follows:
{*}[(0 to 4) or (6,11,41)]
The asterisk allows you to include all branches, no matter what their paths looks like.
It is at present not possible to use the parenthesis to define rule precedence, rules are always evaluated from left to right. It is at present also not possible to use negative integers to identify items from the end of a list.
If you want to know more, join the Webinar on Wednesday!
--
David Rutten
david@mcneel.com
Seattle, WA…
Added by David Rutten at 8:57pm on November 3, 2013
ents but repeated 16 times each. As if to multiply by 16 each one of the original elements.
I am sure that the solution is easy but believe me I tried several things and not get a satisfactory solution, so I write to see if someone comes up with something moreinteresting than me.
thanks in advance.…
ou will see a list of potential matches, sorted from most relevant to least relevant:
Some components and objects support initialisation codes, which means you can assign certain values directly from the popup box. You can do this by adding an equals symbol after the name and then the value you wish to assign. For example, the [Curve Offset] component allows you to specify the offset distance via the popup box by typing =5 after the offset command:
However the popup box also supports a set of special formats that allow you to create specific objects without even typing their names. As of 0.9.0077 (which hasn't been released yet at the time of writing) you can use the following shortcuts to create special objects. In the notation below optional parts of a format will be surrounded by square brackets and hashes (#) will be used to indicate numeric values. So #,#[,#] means;
at least two numeric values separated by a comma, with an optional second comma and third number.
A complete list of special formats (not all of these are supported yet in 0.9.0076):
"∙∙∙ If the format starts with a double quote, then the entire contents (minus any other double quotes) will be placed into a Text Panel.
//∙∙∙ If the format starts with two forward slashes, then the entire contents will be placed in a Text Panel.
~∙∙∙ If the format starts with a tilde, then the entire contents will be placed in a Scribble object.
#,#[,#] If the format contains two or three numerics separated by commas, a Point parameter will be created with the specified coordinates.
+[#] If the format starts with a plus symbol followed by a numeric, then an Addition component will be created.
-[#] If the format starts with a minus symbol followed by a numeric, then a Subtraction component will be created.
*[#] If the format starts with an asterisk symbol followed by a numeric, then a Multiplication component will be created.
/[#] If the format starts with a forward slash symbol followed by a numeric, then a Division component will be created.
\[#] If the format starts with a backward slash symbol followed by a numeric, then an Integer Division component will be created.
%[#] If the format starts with a percent symbol followed by a numeric, then a Modulus component will be created.
&[∙∙∙] If the format starts with an ampersand symbol, then a Concatenation component will be created.
=[∙∙∙] If the format starts with an equals symbol, then an Equality component will be created.
<[*] If the format starts with a smaller than symbol, then a Smaller Than component will be created.
>[*] If the format starts with a larger than symbol, then a Larger Than component will be created.
[# *] Pi If the format contains the text "Pi" with an optional multiplication factor, then a Pi component will be created.
# If the format can be evaluated as a single numeric value, then a Slider will be created with the specified initial value and sensible™ lower and upper limits.
#<# If the format contains two numerics separated by a smaller than symbol, a Slider with the specified limits will be created. The initial slider value will be equal to the lower limit.
#<#<# If the format contains three numerics separated by a smaller than symbol, a Slider with the specified limits will be created. The initial slider value will be the value in the middle.
#..# If the format contains two numerics separated by two or more consecutive dots, a Slider with the specified limits will be created. The initial slider value will be equal to the lower limit.
#..#..# If the format contains three numerics separated by two or more consecutive dots, a Slider with the specified limits will be created. The initial slider value will be the value in the middle.
#/#/[#] If the format contains two or three numerics separated by forward slashes, a Calendar object will be created. The order of value is day/month/year. If year is omitted then the current year is used. Note that a second slash is required because #/# is interpreted as a number and thus results in a Slider.
#:#[:#] [am/pm] If the format contains at least two numerics separated by a colon, a Clock object is created. Seconds are optional, as are am/pm suffixes.
f([...[,...[,...]]]) [= *]If the format starts with a lower case f followed by an opening bracket, an Expression component is created. A list of comma separated arguments can be provided as inputs, and anything after the optional equals symbol becomes the expression string.
Note that decimal places will be harvested from formats that indicate sliders. I.e. the format 0..2..10 is not the same as 0..2..10.00, as the former will create an integer slider from zero to ten whereas the latter will create a floating point slider with two decimal places from zero to ten.…
Added by David Rutten at 3:24pm on February 18, 2013
rmation?" I know that this can already be accomplished using the brilliant Kangaroo plugin, but I wanted a simpler and faster (yet still accurate) single component that could replicate this unique curve using a variety of inputs: the length of the rod/wire, the width/distance between the endpoints, the height of the bend, and the tangent angle at the start. I also wanted make the unknowns (such as height if only length and width are known) easily accessible for plugging into additional components.
The resulting script, being an all-in-one solution, is somewhat unwieldy, but it could easily be broken down into smaller components (custom .gha's which I don't have the ability to code). If someone wants to tackle this, please do! I'm not an expert coder by any means, and as this was only my second time diving into Grasshopper scripting, if the script seems somewhat strange, that's probably why. I did try to comment the code pretty well though. Here's the full description:
--------------------------------------------------
DESCRIPTION: This beast creates the so-called 'elastica curve', the shape a long, thin rod or wire makes when it is bent elastically (i.e. not permanently). In this case, force is assumed to only be applied horizontally (which would be in line with the rod at rest) and both ends are assumed to be pinned or hinged meaning they are free to rotate (as opposed to clamped, when the end tangent angle is fixed, usually horizontally). An interesting finding is that it doesn't matter what the material or cross-sectional area is, as long as they're uniform along the entire length. Everything makes the same shape when bent as long as it doesn't cross the threshold from elastic to plastic (permanent) deformation (I don't bother to find that limit here, but can be found if the yield stress for a material is known).
Key to the formulas used in this script are elliptic integrals, specifically K(m), the complete elliptic integral of the first kind, and E(m), the complete elliptic integral of the second kind. There was a lot of confusion over the 'm' and 'k' parameters for these functions, as some people use them interchangeably, but they are not the same. m = k^2 (thus k = Sqrt(m)). I try to use the 'm' parameter exclusively to avoid this confusion. Note that there is a unique 'm' parameter for every configuration/shape of the elastica curve.
This script tries to find that unique 'm' parameter based on the inputs. The algorithm starts with a test version of m, evaluates an expression, say 2*E(m)/K(m)-1, then compares the result to what it should be (in this case, a known width/length ratio). Iterate until the correct m is found. Once we have m, we can then calculate all of the other unknowns, then find points that lie on that curve, then interpolate those points for the actual curve. You can also use Wolfram|Alpha as I did to find the m parameter based on the equations in this script (example here: http://tiny.cc/t4tpbx for when say width=45.2 and length=67.1).
Other notes:
* This script works with negative values for width, which will creat a self-intersecting curve (as it should). The curvature of the elastica starts to break down around m=0.95 (~154°), but this script will continue to work until M_MAX, m=0.993 (~169°). If you wish to ignore self-intersecting curves, set ignoreSelfIntersecting to True
* When the only known values are length and height, it is actually possible for certain ratios of height to length to have two valid m values (thus 2 possible widths and angles). This script will return them both.
* Only the first two valid parameters (of the required ones) will be used, meaning if all four are connected (length, width or a PtB, height, and angle), this script will only use length and width (or a PtB).
* Depending on the magnitude of your inputs (say if they're really small, like if length < 10), you might have to increase the constant ROUNDTO at the bottom
REFERENCES: {1} "The elastic rod" by M.E. Pacheco Q. & E. Pina, http://www.scielo.org.mx/pdf/rmfe/v53n2/v53n2a8.pdf {2} "An experiment in nonlinear beam theory" by A. Valiente, http://www.deepdyve.com/lp/doc/I3lwnxdfGz {3} "Snap buckling, writhing and Loop formation In twisted rods" by V.G.A. GOSS, http://myweb.lsbu.ac.uk/~gossga/thesisFinal.pdf {4} "Theory of Elastic Stability" by Stephen Timoshenko, http://www.scribd.com/doc/50402462/Timoshenko-Theory-of-Elastic-Stability (start on p. 76)
INPUT: PtA - First anchor point (required) PtB - Second anchor point (optional, though 2 out of the 4--length, width, height, angle--need to be specified) [note that PtB can be the same as PtA (meaning width would be zero)] [also note that if a different width is additionally specified that's not equal to the distance between PtA and PtB, then the end point will not equal PtB anymore] Pln - Plane of the bent rod/wire, which bends up in the +y direction. The line between PtA and PtB (if specified) must be parallel to the x-axis of this plane
** 2 of the following 4 need to be specified ** Len - Length of the rod/wire, which needs to be > 0 Wid - Width between the endpoints of the curve [note: if PtB is specified in addition, and distance between PtA and PtB <> width, the end point will be relocated Ht - Height of the bent rod/wire (when negative, curve will bend downward, relative to the input plane, instead) Ang - Inner departure angle or tangent angle (in radians) at the ends of the bent rod/wire. Set up so as width approaches length (thus height approaches zero), angle approaches zero
* Following variables only needed for optional calculating of bending force, not for shape of curve. E - Young's modulus (modulus of elasticity) in GPa (=N/m^2) (material-specific. for example, 7075 aluminum is roughly 71.7 GPa) I - Second moment of area (or area moment of inertia) in m^4 (cross-section-specific. for example, a hollow rod would have I = pi * (outer_diameter^4 - inner_diameter^4) / 32 Note: E*I is also known as flexural rigidity or bending stiffness
OUTPUT: out - only for debugging messages Pts - the list of points that approximate the shape of the elastica Crv - the 3rd-degree curve interpolated from those points (with accurate start & end tangents) L - the length of the rod/wire W - the distance (width) between the endpoints of the rod/wire H - the height of the bent rod/wire A - the tangent angle at the (start) end of the rod/wire F - the force needed to hold the rod/wire in a specific shape (based on the material properties & cross-section) **be sure your units for 'I' match your units for the rest of your inputs (length, width, etc.). Also note that the critical buckling load (force) that makes the rod/wire start to bend can be found at height=0
THANKS TO: Mårten Nettelbladt (thegeometryofbending.blogspot.com) Daniel Piker (Kangaroo plugin) David Rutten (Grasshopper guru) Euler & Bernoulli (the O.G.'s)
--------------------------------------------------
Edit: More on the math behind this here.
Cheers,
Will
…
Added by Will McElwain at 4:08pm on February 26, 2014
e chosen to dive into Grasshopper. I’m about 6 months in. If some of my comments are completely off, please take that to mean that a feature is too inaccessible to a newish user rather that it’s just missing, as I may have stated.
One of my primary pain points is this. Things that can be done in other programs are invariably easier in other programs. This is a big enough issue that I doubt there’s an easy solution that an armchair qb like myself can offer up.
The interface:
I’ve used a lot of 3D programs. I’ve never encountered one as difficult as grasshopper. What in other programs is a dialog box, is 8 or 10 components strung together in grasshopper. The wisdom for this I often hear among the grasshopper community is that this allows for parametric design. Yet PTC (Parametric Technology Corp.) has been doing parametric design software since 1985 and has a far cleaner and more intuitive interface. So does SolidWorks, Inventor, CATIA, NX, and a bunch of others.
In the early 2000's, when parametric design software was all the rage, McNeel stated quite strongly the Rhino would remain a direct modeler and would not become a parametric modeler. Trends come. Trends go. And the industry has been swinging back to direct modeling. So McNeel’s decision was probably ok. But I have to wonder if part of McNeel’s reluctance to incorporate some of the tried and proven ideas of other parametric packages doesn't have roots in their earlier declaration to not incorporate parametrics.
A Visual Programming Language:
I read a lot about the awesomeness and flexibility of Grasshopper being a visual programming language. Let’s be clear, this is DOS era speak. I believe GH should continue to have the ability to be extended and massaged with code, as most design programs do. But as long as this is front and center, GH will remain out of reach to the average designer.
Context sensitivity:
There is no reason a program in 2014 should allow me to make decisions that will not work. For example, if a component input is in all cases incompatible with another component's output, I shouldn't be able to connect them.
Sliders:
I hate sliders. I understand them, but I hate ‘em. I think they should be optional. Ya, I know I can r-click on the N of a component and set the integer. It’s a pain, and it gives no feedback. The “N” should turn into the number if set. AAAnd, sliders should be context sensitive. I like that the name of a slider changes when I plug it into something. But if I plug it into something that'll only accept a 1, a 2, or a 3, that slider should self set accordingly. I shouldn't be able to plug in a “50” and have everything after turn red.
Components:
Give components a little “+” or a drawer on the bottom or something that by clicking, opens the component into something akin to a dialog box. This should give access to all of the variables in the component. I shouldn't have to r-click on each thing on a component to do all of the settings.
And this item I’m guessing on. I’m not yet good enough at GH to know if this may have adverse effects. Reverse, Flatten, Graft, etc.; could these be context sensitive? Could some of these items disappear if they are contextually inappropriate or gray out if they're unlikely?
Tighter integration with Rhino:
I'm not entirely certain what this would look like. Currently my work flow entails baking, making a few Rhino edits, and reinserting into GH. I question the whole baking thing, btw. Why isn't it just live geometry? That’s how other parametric apps work. Maybe add more Rhino functionality to GH. GH has no 3D offset. I have to bake, offsetserf, and reinsert the geometry. I’m currently looking at the “Geometry Cache” and “Geometry Pipeline” components to see if they help. But I haven't been able to figure it out. Which leads me to:
Update all of the documentation:
I'm guessing this is an in process thing and you're working toward rolling GH from 0.9.00075 to 1.0. GH was being updated nearly weekly earlier this year. Then it suddenly stopped. If we're talking weeks before a full release, so be it. But if we're looking at something longer, a documentation update would help a lot. Geometry Cache and Geometry Pipeline’s help still read “This is the autogenerated help topic for this object. Developers: override the HtmlHelp_Source() function in the base class to provide custom help.” This does not help. And the Grasshopper Primer 2nd Ed. was written for GH 0.60007.
Grasshopper is fundamentally a 2D program:
I know you'll disagree completely, but I'm sticking to this. How else could an omission like offsetsurf happen? Pretty much every 3D program in existence has this. I’m sure I can probably figure out how to deconstruct the breps, join the curves, loft, trim, and so forth. But does writing an algorithm to do what all other 3D programs do with a dialog box seem reasonable? I'm sure if you go command by command you'll find a ton on such things.
If you look at the vast majority of things done in GH, you'll note that they're mostly either flat or a fundamentally 2D pattern on a warped surface.
I've been working on a part that is a 3D voronoi trimmed to a 3D model. I've been trying to turn the trimmed voronoi into legitimate geometry for over a month without success.
http://www.grasshopper3d.com/profiles/blogs/question-voronoi-3d-continued
I’ve researched it enough to have found many others have had the exact same problem and have not solved it. It’s really not that conceptually difficult. But GH lacks the tools.
Make screen organization easier:
I have a touch of OCD, and I like my GH layout to flow neatly. Allow input/output nodes to be re-ordered. This will allow a reduction in crossed wires. Make the wire positions a bit more editable. I sometimes use a geometry component as a wire anchor to clean things up. Being able to grab a wire and pull it out of the way would be kinda nice.
I think GH has some awesome abilities. I also think accessing those abilities could be significantly easier.
~p…
re are major changes and enhancements.
HONEYBEE
More Flexible Workflow - Many small modifications were made to support a more flexible workflow, such as the ability to separate a zone created with masses2Zones into editable HBSrfs that can be recombined. For the energy components, it is now possible to plug custom constructions directly into the components that set the zone constructions without writing them first into the library. For the daylighting components it is now possible to change all of the materials of specific surface types at once.
Support for Complex Geometry - Many small bugs for complex geometry have been fixed including the ability to import energy results correctly for curved NURBS surfaces as well as unconventional window configurations. Also, the intersectMasses component now almost always succeeds in splitting all of the surfaces of adjacent zones, no matter how complex the intersection is.
Automatic Download Issues Fixed - Many users who faced issues with not having “gendaymtx.exe” or who had trouble syncing with our github know that we faced an issue with automatic background downloads.
Air Walls - Honeybee EnergyPlus models now officially support air walls (or virtual partitions) in a basic implementation. Now, any time that you use the air wall construction or set a surface type to “air wall,” the air between adjacent zones will be automatically mixed. At present, this mixing is just a constant flow based on the surface area between zones connected by air walls multiplied by an adjustable “flow factor.” It is important to stress that this basic air mixing is not with the EnergyPlus Airflow Network, although the groundwork laid in this release will eventually allow for the implementation of the Airflow Network in future releases. As such, this present air mixing is only suitable for multi-zone conditions where there is not significant buoyancy-driven flow between zones.
Natural Ventilation - To go along with the new potential introduced by air walls, there has been a basic implementation of EnergyPlus’s natural ventilation objects in a new component called “Set EP Airflow”. The current setup allows for three possible types of natural ventilation: 1) natural ventilation through windows (with auto-calculated flow based on window area, outdoor wind speed/direction, and stack effects), 2) custom wind and stack objects that can be used to model things such as chimneys off of single zones, and 3) constant, fan-driven natural ventilation.
Additional Thermal Mass - The capability to add additional thermal mass to zones has been added. This is useful for factoring in the mass of indoor furniture or heavy interior objects such as chimneys.
New Utility Components - Abraham has added a couple of useful components to help calculate lighting loads based on bulb types and target lighting levels as well as a converter from ACH to the m3/s-m2 that the other HB components accept. Along this vein, there is also a component for adding in the resistance of Air Films to HB constructions.
Improved and Editable Ideal Air Loads System - The EnergyPlus Ideal Air System now goes through an automatic sizing period at the start of the simulation based on the extreme weeks of the weather file. Furthermore, the ability to adjust many of the parameters of the ideal air loads system have been added with a new “Set Ideal Air Loads Parameters” component. The component allows you to add in heat recovery, air side economizers and demand-controlled ventilation.
OpenStudio Export Update - The OpenStudio workflow is still largely under development but this release includes a version with a working VAV and PTHP system template for those curious with experimenting. Note that not all of the new features available for the basic “Run Energy Simulation” component are available for the OpenStudio component (such as air walls, natural ventilation, or additional thermal mass).
Microclimate/Indoor Comfort Maps - Blossoming from initial experiments with the radiant temperature map, a workflow for looking into sub-zone microclimate and indoor comfort has been initiated. All components for this are presently under the Honeybee WIP tab but, over the next month, they will be completing their development phase and moving into the rest of the tabs. If you are interested in testing when they are ready, please let Chris know. For a teaser video of the intended capabilities, see this video: (https://www.youtube.com/watch?v=fNylb42FPIc&list=UUc6HWbF4UtdKdjbZ2tvwiCQ)
LADYBUG
Monthly Bar Chart - After much demand from multiple parties, a new component to create monthly bar and line charts has been added. The component is particularly useful for plotting the outputs of the “Average Data” component like monthly EPW data or averaged monthly-per hour data. It also supports daily data and any type of Energy simulation results.
Wind Profile - To go along with the new capabilities of natural ventilation in Honeybee, Ladybug now has a fully fleshed-out Wind Profile component that allows you to visualize how wind speed changes with height in relation to your building geometry. The component is geared to understanding the conditions of prevailing wind and will be useful in the future for setting up CFD models. Credit goes to Djordje Spasic for adding in all of the new capabilities. In a similar vein, the appearance of the wind rose has also been improved thanks to suggestions from Alejandra Menchaca.
Faster Solar Adjusted Temperature - Thanks to the SolarCal method from the Center for the Built Environment at UC Berkeley (http://escholarship.org/uc/item/89m1h2dg), the solar adjusted temperature component now includes an option for a much faster calculation that produces results that are very close to those originally obtained with the genCumSky component. Instead of using the cumulative sky, the component can now accept the direct and diffuse radiation from the ImportEPW component. Over a whole year, this essentially takes a calculation that used to be a half-hour and shrinks it down to 10 seconds. Thanks again to those at UC Berkeley for keeping their work open source!
Instructions - Last but not the least, [It took me almost two years to understand this but finally] we have a text file that describes the installation step by step and is way easier to modify than a video. You can find it in the zip file. Credit goes to Chris!
We also want to welcome Anton, Patrick and Sandeep to the team. Anton has kicked off his development by working on a component to import and visualize epw ground temperature data and he will be continuing to develop components to bring in reliable precipitation data to Ladybug. With this basis, he will continue to implement Honeybee components for ground heat storage, earth tubes, rain collection and hot water systems. Patrick and Sandeep are working on integration of Honeybee to Energy Performance Calculator.
As always let us know your comments and suggestions.
Enjoy!…
ng is deciding how and where to store your data. If you're writing textual code using any one of a huge number of programming languages there are a lot of different options, each with its own benefits and drawbacks. Sometimes you just need to store a single data point. At other times you may need a list of exactly one hundred data points. At other times still circumstances may demand a list of a variable number of data points.
In programming jargon, lists and arrays are typically used to store an ordered collection of data points, where each item is directly accessible. Bags and hash sets are examples of unordered data storage. These storage mechanisms do not have a concept of which data comes first and which next, but they are much better at searching the data set for specific values. Stacks and queues are ordered data structures where only the youngest or oldest data points are accessible respectively. These are popular structures for code designed to create and execute schedules. Linked lists are chains of consecutive data points, where each point knows only about its direct neighbours. As a result, it's a lot of work to find the one-millionth point in a linked list, but it's incredibly efficient to insert or remove points from the middle of the chain. Dictionaries store data in the form of key-value pairs, allowing one to index complicated data points using simple lookup codes.
The above is a just a small sampling of popular data storage mechanisms, there are many, many others. From multidimensional arrays to SQL databases. From readonly collections to concurrent k-dTrees. It takes a fair amount of knowledge and practice to be able to navigate this bewildering sea of options and pick the best suited storage mechanism for any particular problem. We did not wish to confront our users with this plethora of programmatic principles, and instead decided to offer only a single data storage mechanism.*
Data storage in Grasshopper
In order to see what mechanism would be optimal for Grasshopper, it is necessary to first list the different possible ways in which components may wish to access and store data, and also how families of data points flow through a Grasshopper network, often acquiring more complexity over time.
A lot of components operate on individual values and also output individual values as results. This is the simplest category, let's call it 1:1 (pronounced as "one to one", indicating a mapping from single inputs to single outputs). Two examples of 1:1 components are Subtraction and Construct Point. Subtraction takes two arguments on the left (A and B), and outputs the difference (A-B) to the right. Even when the component is called upon to calculate the difference between two collections of 12 million values each, at any one time it only cares about three values; A, B and the difference between the two. Similarly, Construct Point takes three separate numbers as input arguments and combines them to form a single xyz point.
Another common category of components create lists of data from single input values. We'll refer to these components as 1:N. Range and Divide Curve are oft used examples in this category. Range takes a single numeric domain and a single integer, but it outputs a list of numbers that divide the domain into the specified number of steps. Similarly, Divide Curve requires a single curve and a division count, but it outputs several lists of data, where the length of each list is a function of the division count.
The opposite behaviour also occurs. Common N:1 components are Polyline and Loft, both of which consume a list of points and curves respectively, yet output only a single curve or surface.
Lastly (in the list category), N:N components are also available. A fair number of components operate on lists of data and also output lists of data. Sort and Reverse List are examples of N:N components you will almost certainly encounter when using Grasshopper. It is true that N:N components mostly fall into the data management category, in the sense that they are mostly employed to change the way data is stored, rather than to create entirely new data, but they are common and important nonetheless.
A rare few components are even more complex than 1:N, N:1, or N:N, in that they are not content to operate on or output single lists of data points. The Divide Surface and Square Grid components want to output not just lists of points, but several lists of points, each of which represents a single row or column in a grid. We can refer to these components as 1:N' or N':1 or N:N' or ... depending on how the inputs and outputs are defined.
The above listing of data mapping categories encapsulate all components that ship with Grasshopper, though they do not necessarily minister to all imaginable mappings. However in the spirit of getting on with the software it was decided that a data structure that could handle individual values, lists of values, and lists of lists of values would solve at least 99% of the then existing problems and was thus considered to be a 'good thing'.
Data storage as the outcome of a process
If the problems of 1:N' mappings only occurred in those few components to do with grids, it would probably not warrant support for lists-of-lists in the core data structure. However, 1:N' or N:N' mappings can be the result of the concatenation of two or more 1:N components. Consider the following case: A collection of three polysurfaces (a box, a capped cylinder, and a triangular prism) is imported from Rhino into Grasshopper. The shapes are all exploded into their separate faces, resulting in 6 faces for the box, 3 for the cylinder, and 5 for the prism. Across each face, a collection of isocurves is drawn, resembling a hatching. Ultimately, each isocurve is divided into equally spaced points.
This is not an unreasonably elaborate case, but it already shows how shockingly quickly layers of complexity are introduced into the data as it flows from the left to the right side of the network.
It's no good ending up with a single huge list containing all the points. The data structure we use must be detailed enough to allow us to select from it any logical subset. This means that the ultimate data structure must contain a record of all the mappings that were applied from start to finish. It must be possible to select all the points that are associated with the second polysurface, but not the first or third. It must also be possible to select all points that are associated with the first face of each polysurface, but not any subsequent faces. Or a selection which includes only the fourth point of each division and no others.
The only way such selection sets can be defined, is if the data structure contains a record of the "history" of each data point. I.e. for every point we must be able to figure out which original shape it came from (the cube, the cylinder or the prism), which of the exploded faces it is associated with, which isocurve on that face was involved and the index of the point within the curve division family.
A flexible mechanism for variable history records.
The storage constraints mentioned so far (to wit, the requirement of storing individual values, lists of values, and lists of lists of values), combined with the relational constraints (to wit, the ability to measure the relatedness of various lists within the entire collection) lead us to Data Trees. The data structure we chose is certainly not the only imaginable solution to this problem, and due to its terse notation can appear fairly obtuse to the untrained eye. However since data trees only employ non-negative integers to identify both lists and items within lists, the structure is very amenable to simple arithmetic operations, which makes the structure very pliable from an algorithmic point of view.
A data tree is an ordered collection of lists. Each list is associated with a path, which serves as the identifier of that list. This means that two lists in the same tree cannot have the same path. A path is a collection of one or more non-negative integers. Path notation employs curly brackets and semi-colons as separators. The simplest path contains only the number zero and is written as: {0}. More complicated paths containing more elements are written as: {2;4;6}. Just as a path identifies a list within the tree, an index identifies a data point within a list. An index is always a single, non-negative integer. Indices are written inside square brackets and appended to path notation, in order to fully identify a single piece of data within an entire data tree: {2,4,6}[10].
Since both path elements and indices are zero-based (we start counting at zero, not one), there is a slight disconnect between the ordinality and the cardinality of numbers within data trees. The first element equals index 0, the second element can be found at index 1, the third element maps to index 2, and so on and so forth. This means that the "Eleventh point of the seventh isocurve of the fifth face of the third polysurface" will be written as {2;4;6}[10]. The first path element corresponds with the oldest mapping that occurred within the file, and each subsequent element represents a more recent operation. In this sense the path elements can be likened to taxonomic identifiers. The species {Animalia;Mammalia;Hominidea;Homo} and {Animalia;Mammalia;Hominidea;Pan} are more closely related to each other than to {Animalia;Mammalia; Cervidea;Rangifer}** because they share more codes at the start of their classification. Similarly, the paths {2;4;4} and {2;4;6} are more closely related to each other than they are to {2;3;5}.
The messy reality of data trees.
Although you may agree with me that in theory the data tree approach is solid, you may still get frustrated at the rate at which data trees grow more complex. Often Grasshopper will choose to add additional elements to the paths in a tree where none in fact is needed, resulting in paths that all share a lot of zeroes in certain places. For example a data tree might contain the paths:
{0;0;0;0;0}
{0;0;0;0;1}
{0;0;0;0;2}
{0;0;0;0;3}
{0;0;1;0;0}
{0;0;1;0;1}
{0;0;1;0;2}
{0;0;1;0;3}
instead of the far more economical:
{0;0}
{0;1}
{0;2}
{0;3}
{1;0}
{1;1}
{1;2}
{1;3}
The reason all these zeroes are added is because we value consistency over economics. It doesn't matter whether a component actually outputs more than one list, if the component belongs to the 1:N, 1:N', or N:N' groups, it will always add an extra integer to all the paths, because some day in the future, when the inputs change, it may need that extra integer to keep its lists untangled. We feel it's bad behaviour for the topology of a data tree to be subject to the topical values in that tree. Any component which relies on a specific topology will no longer work when that topology changes, and that should happen as seldom as possible.
Conclusion
Although data trees can be difficult to work with and probably cause more confusion than any other part of Grasshopper, they seem to work well in the majority of cases and we haven't been able to come up with a better solution. That's not to say we never will, but data trees are here to stay for the foreseeable future.
* This is not something we hit on immediately. The very first versions of Grasshopper only allowed for the storage of a single data point per parameter, making operations like [Loft] or [Divide Curve] impossible. Later versions allowed for a single list per parameter, which was still insufficient for all but the most simple algorithms.
** I'm skipping a lot of taxonometric classifications here to keep it simple.…
Added by David Rutten at 2:22pm on January 20, 2015