Grasshopper

algorithmic modeling for Rhino

Dear Users,

I've been working on data tree selection rules this weekend and when 0.9.0063 is released (hopefully tomorrow, 4th November) the [Path Compare], [Tree Split] and [Replace Path] components 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.

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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

Views: 57447

Replies to This Discussion

Is there any chance to use it this way?

Not yet.

--

David Rutten

david@mcneel.com

The problem is : how do I use these rules when I can't type either {} or [] because the AltGr key is not allowed in GH ?

Now I have hundreds of path masks that are refused by my Split Tree components in this new version because using only 0;0 instead of {0;0} is not possible anymore.

I can rewrite my path masks using Concatenate, but I still have to copy-paste the brackets from the notepad.

The AltGr key is not a shortcut in GH, why is it impossible to use it to type characters ?

AltGr is perfectly fine in editing Panels and GraphMapper.

You can't use AltGr, when you edit a value through the menu, but that isn't good practice anyway. In menus Alt and AltGr are reserved by the system and used to navigate menu items.

If you absolutely have to set Path masks as persitent data in the parameter, use "Manage Text Collection". You will not be able to use the AltGr key there.

I've always used the US keyboard layout, no need for AltGr and the keys assigned to some characters are easier to access, I think it's better for writing code.

You can always alt-shift to change to another keyboard layout to type special local characters.

thanks david,

it makes the editing of data list more efficent!

Hi David,

is the "or" and "and" not working, if I want to select a set within a tree, but only with list items or am I missing something here?

First Mask shows, what I want to achieve.

Second Mask shows my attempt using "and" within the tree.

Third Mask shows my confusion of setting brackets in this case, since "[" and "]" would also refer to item list.

Best,

Phillip

Hi Phillip,

The AND operator means both conditions need to be satisfied. For an integer to pass your rule, it must be both equal to 35 AND be between zero and one. No such integer exists. You need OR.

Doh. Sorry.. Monday morning.

Hi all,

I'm using another laptop and I got this error message, it also doesn't work through manage path collection either.

I've checked the keyboard layout and it's English(US). I rarely use the question tag for a path mask, 

I really don't have a clue for this problem. Any idea?

Thanks

ergh.. sorry, David. My bad, I didn't read your mention about the supported compoonents 

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