How to get the outline of overlapped shapes?

Hello all,

I'm a beginner in Grasshopper so if I'm not make sense so please bear with me.

I've generated some snowflakes in 2D with a messy grasshopper script (is this how it's called?) and I'm having a hard time to get the outline profile of each of them. I tried using Region Union and some of the bits came up missing randomly. I also tried Mesh Shadow but it's not giving me just the outline profile (it's giving me the internal lines as well).

I tried baking it and then use the Rhino command MeshOutline onto each of them individually and it works sometimes, but it's still missing some random pieces sometimes.

Is there a way to elegantly and perfectly trace out the outline profiles of each of the snowflakes? (preferably in Grasshopper so it can be automatic)

I've attached the GH file and a screenshot to explain my problem.

Thanks,

Ching

Attachments:

ghhelp06jan2012.png, 297 KB

Replies to This Discussion

Permalink Reply by kleerkoat on January 6, 2012 at 6:57am

Just posting to say that is a cool definition!

Permalink Reply by Ching on January 6, 2012 at 9:27am

Thanks for the reply Ryles.

I'm wondering if it could be just a natural limitation of Rhino or GH of processing too much information, or something like that, that could be causing the random missing bits. Could that be the case or is it just my computer? (Stealth bumping my post)

Permalink Reply by Kristjan on January 6, 2012 at 10:12am

I would do the outlines with Region Union component in GH. For doing that you need to use Pathmapper first to flatten the pieces by snowflakes...The drawback is that it also misses some flakes (see te picture or GH definition).

Attachments:

RegionUnion.png, 464 KB

Permalink Reply by Ching on January 6, 2012 at 10:56am

Thank you very much Kristjan, that solved the problem pretty much.

Actually do you mind taking the GH definition off the site please? My boss just put pressure on me to keep the definition out of circulation. I'm really grateful if you can delete that link to the gh file, many thanks. You can keep the file to yourself :)

Permalink Reply by Yoann Mescam (Systemiq) on January 6, 2012 at 3:57pm

Frustrating! I wanted to take a look, but without looking at it I would have suggested to play with Rhino tolerance (setting it to 0.1 perhaps ?).

Permalink Reply by Ching on January 6, 2012 at 5:07pm

I apologise for the teasing. I'm aware it's making me the bad guy but please understand I'm under pressure to withdraw the files, and if it's not office related stuff (sort of) I will be more than happy to share :P

I tried playing with the rolerance in Rhino but it wasn't the issue it seems. Thank you for the input tho.

The definition itself is nothing more than spikes of random sizes poking out at different points along a line, and then rotated (copypasted) 6 times to form a snowflake. I'm quite sure anyone would be able to build one because even I can do it and I'm just a beginner, it's more or less my first grasshopper project.

Permalink Reply by mohamed aly on July 30, 2012 at 6:50am

Hi Kristian,

I am trying to do something similar in grasshopper. I have 6 shapes that overlap and intersect and I need their outline shape. I think you have a way. I tried to use the pathmapper which I am not familiar with.

Can you explain more or upload a definition capable of this?

Thank you,

Permalink Reply by Kristjan on July 30, 2012 at 7:25am

Hi,

All it needs is Region Union component (see attached)- the pathmapper was used because of more complex data structure.

Attachments:

Outlines.gh, 8 KB
Outlines.png, 144 KB

Permalink Reply by mohamed aly on September 6, 2012 at 5:33am

Thank you ... appreciated

Permalink Reply by Fahimah Badrulhisham on September 5, 2012 at 9:37pm

Hi everyone,

I'm a uni student, new to GH. I've been working on a definitition for snowflakes based on Raja Isaa's fractal definition from the Rhino website. While I have had some minor success with the definition, it's quite messy and nowhere near as cool as Ching's :s

I know Ching's office is keen to keep his definition out of circulation, but would it be at all possible for someone to provide hints or steps as to how it was achieved?

Thanks!

Permalink Reply by Ching on September 6, 2012 at 5:44am

The way I made it: it was just a matter of rotation of long hexagons at different places, imagine a line and there is random dots on it, and you want hexagons to come out of those points at random lengths. Tricky part was to made a parametric hexagon of variable length while maintaining the shape of the ends (of 60 degree angles). The rest was just lots of randoms and rotations (and booleans to combine them).

But if I were to do it again I would try Hoopsnake it to achieve a more fractal result (the snowflakes in this thread were very simple actually, with just one brach of spikes coming out of just one trunk).

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