Grasshopper

algorithmic modeling for Rhino

Hi everyone,

I am a grasshopper newbie. I am trying to model ribs arrayed on an onion dome, trying to make it look like in the attached photo. I know how to achieve the surface in the shape of a dome, however i have no clue how to even tackle the ribs.

I need to be able to control the number ribs, the number of nods (or the cross-overs) and where on the surface they cross over.

Sorry for a clumsy decription (an the dreadful drawing above), as i said I don't reallyknow the grasshopper terminology.

Any tips please?

Thanks

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How about this, It will only work on a symmetrical shape mind.

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Hi Matt,

thanks for your reply!

I have created a curve from points to use as the dome profile.

The lines seem to be not attached to the top, i am not sure why?

I think its just you have draw the curve from points the other way up (Your start and end points are opposite to mine) . Click on the points component and select reverse from the drop down list. or just re-select the point starting at the bottom and working your way to the top. 

works great, thanks a lot!

I've made several small parts like that: http://www.thingiverse.com/thing:1319930 but had trouble with the top point. The ribs ended up making a small flat area so I cheated and added a tiny cone to the top. 

Hi Birk,

How did you construct these? They look great 3d printed!

Thanks gosia, I'm glad you like my designs. For parts like this the process is pretty straightforward (because I am a self-taught GH user), but the actual GH layout get somewhat complex because of the requirements for making a valid 3D printable part. The basics are these:

1. Construct the curve forming the shape of the part (I use 6 points and an interpolated curve.)

2. Use this curve to make a Sweep1 surface

3. Extrude a small square along this same curve to make a make a square-shaped ridge and cap it. (I've tried triangles too.) 

4. Make a circular Curve Array of 3 specifying the number of ribs you want. Be sure to use a rail curve that matches the sweep curve in 1.

5. Twist these ribs a specified # degrees, and then twist them the same number of degrees in the opposite direction.

6. Join 1 & 5 and you're done - almost.  As I said, the top of the part will be flat, so I add a small circular cone to make it come to a nice point.

For 3D printing I had to give the basic surface thickness so I could control the amount of light transmitted through it, and also to eliminate naked edges, so Step 2 is actually more complicated than I indicated above. 

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