Length goal vs equal length goal - Kangaroo

Hi,

Could anyone tell me what the difference is between specifying these two goals:

(1) equal length goal

(2) length goal with the target length as the average length of all lines

The reason I'm asking is that I want to equalise a number of different sets of lines and obviously turned to using the equal length goal, however I couldn't get it to work with a datatree of lines (each list should be equalised individually hence use of datatree). Why doesn't this work and is average target length a good workaround?

Cheers,

Sam

Replies to This Discussion

Permalink Reply by Daniel Piker on November 26, 2015 at 3:26am

Hi Sam,

The equal length goal tries to make the length of each line in the list equal to the average of their current lengths. This updates itself constantly during simulation. If you make a triangle and apply an equal length goal to its 3 edges then drag its points using Grab, you will see it remains equilateral, but can change in size.

If instead you take the average yourself upstream of Kangaroo and use a Length goal, the same triangle would become equilateral with a fixed edge length, which would not change unless you change the input.

Not sure about your datatree issue without seeing it, but remember that EqualLength takes a list for the Line input. If you want to apply it to multiple sets of lines, they should be in a tree with each set as a list on a separate branch.

Permalink Reply by Sam Gregson on November 27, 2015 at 7:41am

Hi Daniel,

Thanks very much for your response. What you have said makes sense and therefore it seems that Equal Length goal is what I want in my case.

It turns out that Equal Length goal does work when I use in conjunction with Length goal, so that is what I have opted for with Length goal set at a very low strength.

However, the results I get are not great, my average and maximum length deviations are worse for the kangaroo output compared with the original input. What can I do to get this to work properly?

I am aware that I have added some additional restraints and therefore don't expect any miracles but I wasn't expecting the solution to be worse!

Any tips much appreciated. I have attached my file.

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