Designing geodesic dome

[janeks]

Hi,

I am beginner of FreeCAD.
At the beginning I was a bit worrying will it not be too difficult, but despite some comments on internet (seems that they ar outdated) it was was easy enough by using docs and tutorials to get on the basic line.

But wee what I want to do is to design geodesic dome building.
I used some ideas from here:
https://www.youtube.com/watch?v=XdZYc55JrmA

While I could not it to do with Sketcher, but with Draft I managed to make basic 1V Icosahedron.

skreen1.png (159.43 KiB) Viewed 6180 times

Now I would like to split basic triangles

skrren2.png (302.85 KiB) Viewed 6180 times

And project the cross points on surface of sphere.
For that I would need to draw the line from the center of the sphere trough that point and find the crosspoint with surface of the sphere. Or draw the arc trough the basic triangle points and then find crosspoint of the arc.

So the questions could be:
What would be the best way to achieve this?
How it could be automated? So that I can repeat or clone and fill the sphere with the same parts, but in other sections of sphere?

brgds&
Thanks in advance!
Janeks
on
OS: Ubuntu 12.04.5 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.15.4368 (Git)
Branch: master
Hash: 845849fa91c47e849b567f499c3e99f4be845373
Python version: 2.7.3
Qt version: 4.8.1
Coin version: 3.1.3
OCC version: 6.7.1

[NormandC]

Hello Janeks,

A search of the word "geodesic" gives these results:

search.php?keywords=geodesic

[janeks]

I looked also trough this search, but I saw just the same approach for beginning used here:
viewtopic.php?f=3&t=7118&hilit=geodesic&start=20#p57624

But how to go further...?

[whirlybomber]

janeks,

I did this once in CATIA, but have not tried it in FreeCAD. You would need to use the Assembly2 macro to see if it can be done.

All you do is model the smallest basic elements (triangles) and then assemble them to make the bigger dome (working "up" from the smallest parts, rather than working "down" from the final solid as you apear to have done). Once you have your basic triangles, you just add themm together in an assembly, constraining them along the edges and at the vertexes of the triangles. As you go through adding more triangles, if you are constraining them correctly, you will end up with a dome structure. You do have to be careful to make sure each group of constraints "closes" the dome in the same direction, or you can end up with a wobly sort-of plane that isn't what you are after. But it is quite obvious when that goes wrong.

[janeks]

Thank you - now I again on the way. The kewords was "mapping sketch on surface".
So I created the wired triangle from center point and two "sphere surface points", then got surface which used to map a sketch.
In this case I based start not to draft objects, but created sketches on base paneswith two triangles, that formed golden cut rectangles.

2vDomeBasic.png (192.66 KiB) Viewed 6097 times

It gives mo some more play an skills in freeCAD regarding constraints.
They seems to be very powerful. Here also the question, that I probably will put on different topic:
How could I create constrains between sketches on different plans?

It would be nice if I could create a basic for dome, where I can change basic constraint - the radius and it will changes other elements accordingly...

[janeks]

Final work result for V2 here:
viewtopic.php?f=24&t=9202

Future plans - to script that so that by inputting center coordinates, giving radius and level of detail it would generate base for geodesic surface(s).
Also here the question:
How create mesh differs?
I can get similar results with meshing of sphere, but they ar no so "perfect"...

brgds
Janeks on:
OS: Ubuntu 12.04.5 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.15.4368 (Git)
Branch: master
Hash: 845849fa91c47e849b567f499c3e99f4be845373
Python version: 2.7.3
Qt version: 4.8.1
Coin version: 3.1.3
OCC version: 6.7.1

[ulrich1a]

So the questions could be:
What would be the best way to achieve this?
How it could be automated? So that I can repeat or clone and fill the sphere with the same parts, but in other sections of sphere?

I got inspired by this post and created a macro to generate a geodesic dome shell: http://www.freecadweb.org/wiki/index.ph ... odesicDome

attached also here:

geodesic_dome.py.zip

(2.99 KiB) Downloaded 269 times

Ulrich

[janeks]

...
I got inspired by this post and created a macro to generate a geodesic dome shell: http://www.freecadweb.org/wiki/index.ph ... odesicDome

Ulrich

Thank you Ulrich.

Uh, nice - that is the power of open source ...

What I would do for some practical reasons:
Visualize the equal triangles and borders with different colors.
Create some statistics how much each of them are equals.
Could be also on angles.
It is quite useful when building one. But when building we would need some part of whole sphere. So it would be better to get some statistics after cutting.
I guess there is already some tools for that... quick search did not give me results yet... will try latter.

brgds
Janeks

[rockn]

Ulrich, your macro is awesome !
I made a little icon for this to add a nice button on a gui toolbar.
Feel free to add this to the wiki :

GeoDom.svg

(38.99 KiB) Downloaded 374 times

[janeks]

Are there any way how could I put constraints on these geodetic?
F.ex. if I would like to set radius as a constraint?