Stereographic projection

Hello all,

I would like to map the night sky onto a hemisphere.

I have found a website that allows you to input latitude longitude co-ordinates and it provides a map of the sky with constellations and other information as seen from the specified location. So I have a picture of the sky as curves that I traced in illustrator which is a flat circle and have imported into grasshopper.

Is it possible to map this onto a hemisphere and maintain the correct proportions. I'm sure grasshopper could provide this functionality but my attempts so far have been unsuccessful. I have mapped the curves onto the surface but cannot get the perimeter curve/circle to align with the base of the hemisphere.

Its proving to be a bit tricky!

Any ideas?

Many thanks

Chris

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sky mapping forum question.gh, 45 KB

Replies to This Discussion

Permalink Reply by Chris Ingram on November 28, 2012 at 6:55am

OK i think i found a way to do it, just explode all the curves then project them upwards and intersect with the surface then join up the curves after sorting. It seems quite obvious now i think about it. :)

Permalink Reply by Rémy Maurcot on November 28, 2012 at 6:57am

Hi Chris,

Please look the definition:

Attachments:

skymappingforumquestion.gh, 47 KB

Permalink Reply by Chris Ingram on November 28, 2012 at 7:09am

Hi Remy,

Thanks for your reply, I actually found that as my input is from a circle map of the sky - most of the work has already been done in terms of mapping from the output i already made in illustrator. I think i can extrude the curve then brep brep intersection on the hemisphere to get the curve. It may not be 100% accurate but will definitely do for now...

Many thanks

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