Flow along surface - sphere

Hi - I’m trying to wrap a floor plan around part of a sphere but I can only get it to distort in one direction.
Attached a 3dm showing the original plan, then base surface, target surface, and flowed result for each one.

The first target surface is made from 2 isocurves of a sphere which are then joined with lines that are ‘straight’ in the z dimension. Second target surface is from 4 isocurves of a sphere (i.e. symmetrical in two dimensions not just one).

The base surface for each is then made by doing a CreateUVCurves / PlanarSrf on the part of each sphere. I use Dir to check base and target surfaces are in alignment.

The first one is closer to what I want (i.e. partial distortion, not flowing it around the whole sphere.) I’m not sure why in the second version it flows the original geometry around a whole sphere instead of just part of that sphere. But the general problem is that it distorts in one dimension - i.e. if you look at it in Top view, 2 sides of the square are still parallel.


150308_alex_forum.3dm (2.1 MB)

150308_alex_forum.pdf (79.2 KB)

Hi Alex - use ShrinkTrimmedSrf on the trimmed sphere to get what I think you want from FlowAlongSrf.


Thanks Pascal
The ShrinkTrimmedSrf works great on the trimmed sphere - it no longer flows around the whole sphere, just that surface.
My problem of it distorting in only one dimension is still happening though…any idea what I can do about this?

I just tried FlowAlongSrf using a target surface that was actually a Sweep2 - along the boundary curves of the original trimmed sphere. This seems to work - i.e. it distorts in both directions. I think it’s something to do with the UV directionality of a sphere vs. a swept surface? This isn’t ideal though because the swept surface isn’t totally coincident with the original sphere - which is going to give me a headache later down the line for what I want to do.

Is there any way of altering the UV makeup of the trimmed sphere so that it distorts in both directions?

I guess I am being dense about what the goal is - it is not this, I guess? You wand the lines to puff out top and bottom as well, correct?

Is this more like it?

150308_alex_forum_PG.3dm (2.0 MB)


Yes - that’s exactly what I want!

How did you do that?!

Hi Alex- the trick is to distort the base surface ‘oppositely’, to borrow from Calvin and Hobbes, to the way you want the eventual distortion on the target. The problem is the UV is parallel (think of latitudes on a globe) in the across, or East-West direction on your sphere and on the base surface as well so there is no distortion in the North-South direction. So, distorting the base surface (note History is on in my example file so you can monkey with the points on the base surface to edit the result) in that direction forces the distortion on the target. I changed the degree of the base surface to 2 by 2 so that I could get that middle point to mess with.


Gotcha, thanks!
I guess this is basically by eye and there is no real way to do it ‘accurately’ ? … i.e. get something that would give you a symmetrically distorted result?

Hi Alex- there might be a way to reproduce the structure of the sphere more exactly in a flat version, but I am not sure it is worth the effort- the attached may be a little closer - I used InsertKnot and InsertKink and adjusted point weights to match the UV of the surfaces up.

150308_alex_forum_PG2.3dm (2.1 MB)

Dunno if I did any good…