Random Cull using Galapagos to form desired shadow

Replies to This Discussion

Permalink Reply by David Rutten on January 21, 2012 at 1:28am

Hi Jake,

starting at the beginning, Galapagos requires one or more sliders  to modify. So unless your model can be controlled (in a somewhat continuous fashion I might add) via sliders, there's no point in going down the Galapagos route.

What exactly are the variables involved in this truss of yours? How many are there? What do they embody?

Alternatively, would it be possible to approach this from the opposite direction? Instead of generating a truss whose shadow fits into a boundary, why not create a much larger truss and remove all those parts whose shadow is outside the boundary? Reason I ask is that this sounds like a very under-constrained problem. I can imagine there's probably a very large amount of different trusses whose shadow is inside a boundary, there is however only one minimal reduction of an existing truss that adheres to the same constraint...

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Jake Alsop on January 21, 2012 at 2:00am

Thanks for the quick response David,

Basically I am looking to design a structure for the burning man festival and want to explore the possibility of the truss revealing a symbol in its shadow projection at a certain time of the day. The truss is based on a quasicrystal lattice and is built manually so cant be controlled by sliders. 

My thinking was that if I could draw the desired shape on the ground within the current shadow projection then cull the truss which creates shadows outside the boundary > so your second suggestion sounds more appropriate.  How would be the best way to remove these elements from the structure?

Many thanks,

 

Jake

Permalink Reply by David Rutten on January 21, 2012 at 2:13am

I attached one possible approach. I'm using Mesh-Ray intersections to determine for each end-point of a single truss element whether it's inside or outside the boundary. Only if both endpoints cast a shadow inside the boundary is the element allowed to exist.

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Attachments:

• ShadowOutlineCull.gh, 93 KB

Permalink Reply by Jake Alsop on January 21, 2012 at 2:14am

that sounds brilliant, will have a play now. thank you very much

 

Jake

Permalink Reply by David Rutten on January 21, 2012 at 2:25am

Incidentally, if the boundary is highly concave, then this may result in elements that do cast shadows outside of the allowed region. If this is a problem some additional testing will need to be added.

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Karol Wawrzyniak on April 18, 2012 at 2:58am

Hi David,

I had a look on your file.

"Complete truss" is just a single line component with line colection inside.

Could you write how did you create this line colection just inside line component?

(for me it would take some canvase space to make such a truss arrangement)

best,

karol

Permalink Reply by David Rutten on April 18, 2012 at 8:14am

Hi Karol,

I honestly don't remember. It may well have been made in Rhino using the Array command, then imported into Grasshopper using a Curve parameter, then connected to a Line parameter which subsequently got 'internalised'.

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Karol Wawrzyniak on April 18, 2012 at 2:29pm

Hi David,

Thanks for fast replay.

I was not familiar with 'internalised' posibility- i learned something again:)

(Nice that you can share just one file - makes it easier for some cases)

best

karol

Permalink Reply by David Rutten on April 19, 2012 at 1:48am

Be careful using Internalise on Rhino4 btw. I've had reports that Curves and often Surfaces and Breps do not properly deserialize themselves. It seems to work consistently only in Rhino5.

--

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Karol Wawrzyniak on April 19, 2012 at 2:18am

thanks for worning i will be cearfull with that.

best

k