Any suggestions on how to model spirals onto a sphere which go from pole to pole?
Cheers
Rainer

Hi Rainer re: spiral on a sphere - if you can draw a curve that is close to what you want, you can then sweep a line along it to get a kind of ribbon like surface and then intersect that with the sphere to get your final curve.

Check out Danny's post in this previous thread for that kind of method:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3530.1

But it may be kind of difficult to get the path shaped well in the pole areas.

- Michael

Hi Rainer,

The method Michael mentions is the way to go, here's a quick run-down for you and anyone else who's interested.

Create a regular Helix, 'Draw curve > More > Helix'
Draw a line (Green) perpendicular from the start of the Helix to the centre.


Sweep the Green line along the Helix 'Construct > Sweep' and use 'Flat' in the Twist option drop down.


Create a Sphere 'Draw Solid > Sphere' from the centre of the helix and use the end point of Helix for the size.


Then use 'Construct > Curve > Isect' to create an intersection curve between the Sphere and Swept surface, and you have what I call a 'HeliSphere'


Then have fun with it!


Cheers

Hey Danny, that turned out better around the pole area than I thought it might, cool!

- Michael

Yeah Michael, I was happy with it too!
The curve is good as is, but further refining with 'rebuild' and you get a nicer curve with evenly spaced control points.

Cheers

Danny,
How did you cut the curve perpendicular to the surface in the rendered example?
Thanks,
David

Hi Danny,

Thanks for this Tip, very handy to know.

regards Colin

Hi David,

> How did you cut the curve perpendicular to the surface in the rendered example?

I actually swept an arc profile which is the same radius as the sphere (in blue) to get the result in the rendered picture.
Is this what you mean?





Cheers

Magic sweep! ;)

Thanks Danny,
I did not realize it would track the spiral perpendicularly. I assumed you were doing something more exotic.
- David

During the sweep you can fix or not the twist (free or fixed) ;)

Ah yes... Thanks Frenchy Pilou.