Approach to distribute objects randomly while avoiding intersection

Dear community,

I am new to grasshopper and as I learned in the introduction video one should work into grasshopper by trying to solve a specific project. My problem is, I don't know how to approach the solution and I'm hoping for hints which way to go...

The goal

...is to have grasshopper randomly distribute a certain amount of sticks in a certain angle (or range of angles) in a certain area without them colliding with each other.
In this example I did it manually, but I'd like to do it in parametrically in the future (altering amount, angle, area, diameter, length...).

My (pseudo) logic:

set counter //amount of sticks
loop counter {
   make instance of stick on random point in area   // cf. populate
   rotate stick within parameters   // tilt and rotate
   try to intersect all sticks
   if (intersection = TRUE) {
       delete current instance of stick
       exitcounter++   // don't want to get stuck in the loop
   }else{
       counter++
   }
   if exitcounter > max {
       exit
       }
}

My thoughts:

The crucial part is avoiding the intersections
As I understand, it is not possible to make loops with standard grasshopper components. I tried Hoopsnake, but it would overwrite the instance of the stick each iteration, making the intersection impossible.
Galapagos: I could set up all instances of sticks at once an define their rotation/tilt as genes, where the fitness value would be a false result for trying to intersect all instances. But galapagos doesn't allow for boolean values, and it doesn't seam very straigt forward anyways.
I'll have to script it which have to learn first...

Cheers,
d@2T

Replies to This Discussion

Permalink Reply by Brian Harms on March 20, 2017 at 2:12pm

You could also just create a bunch of sticks that are randomly placed/angled, and just cull all the ones that happen to have intersections.

Permalink Reply by Brian Harms on March 20, 2017 at 2:35pm

Here is an example of that

Attachments:

pipe intersections.gh, 11 KB

Permalink Reply by d@2T on March 21, 2017 at 6:01am

This is actually one approach I thougth of, but I wasn't able to put it into practice properly. The downside here in my opinion is the difficulty to control the resulting amount of sticks - which is crucial to me.
But this sounds like a case for galapagos, where the the gene would be the seed to randomize points and the fitness would be the resulting amount of pipes that don't intersect?

My thanks, anyway!

Permalink Reply by Joseph Oster on March 20, 2017 at 3:29pm

Anemone - This was fun. You could use 'Fast Loop' but it's fun to watch.

I see that Brian Harms has done a version without looping. Interesting approach but different model so different results.

Attachments:

sticks_2017Mar20a.gh, 25 KB

Permalink Reply by Joseph Oster on March 20, 2017 at 7:56pm

This is a better version of the Anemone loop approach to this challenge. More robust, more fun to play with and watch. The green "X' points are the ones that remain unoccupied, the blue pipe is the one being tested. The basic idea is simple. What is quite challenging in Grasshopper, compared to conventional programming languages, is the lack of "if ___ then" to avoid possible error conditions. Instead, both possibilities must be generated and then the correct one selected with 'Stream Filters'.

This is what it looks like when that loop finishes - none of the pipes collide.

Attachments:

sticks_2017Mar20b.gh, 29 KB

Permalink Reply by d@2T on March 21, 2017 at 6:09am

This is freakin amazing, just what I was looking for! Though it will take some time to comprehend this gem, I will try to implement the option to place external 'colliders' to leave out certain spaces (imagine placing a sphere somwhere in this tangle and omit sticks that intersect with it).

Thank you so much!

Permalink Reply by Joseph Oster on March 21, 2017 at 7:07am

Adding fixed obstacles is extremely easy.

Attachments:

sticks_2017Mar21a.gh, 34 KB

Permalink Reply by Viola Cambié on May 7, 2020 at 3:51am

Great work!

Starting from your example I would like to try a similar exercise: positioning circles going farther from a specific point and not shuffling the list every iteration.

Any suggestion on how to achieve this?

Thanks in advance!

Permalink Reply by d@2T on March 21, 2017 at 10:24am

Thank you Joseph Oster, this does right what I was looking for and the time will come that I also understand how it does it.
To reproduce the initial design I changed some slight details for my purposes, like mirroring the tubes, rotating them against z-axis with step-wise angles, using rhino geometry for the area and using meshes as external colliders.

Its now easy to use different shapes

Attachments:

2017-03-21_JO-solver-mirrored.gh, 29 KB

Permalink Reply by Joseph Oster on March 21, 2017 at 11:12am

Looks like you understand it well enough to use it - cool! Would love to see your work but you forgot to internalize your reference curves and meshes. Right-click those params and "Internalize data" to avoid having to send a Rhino file.