Projection questions, exact placement on hemisphere

I need to project the curves for the sections to be extruded on the white top hemisphere of this design.
I have been experimenting, but keep getting tapering.
Can anyone offer some advice to get a uniform projection on a surface this shape.
Thank you all.

Hi @Simon_Jackson,

If you are starting with a defined outer surface of a panel and you want to end up with a solid panel, put a point on the surface roughly where you judge the centre to be. Then use ExtrudeSrf (the straight extrusion) with the solid option to create a solid from your surface, using your surface point and the centre of the sphere for the direction. Use BooleanDifference to subtract the sphere from it.

If you just want a curve marking the intersection between the sphere and the panel sides, use ExtrudeSrf with solid=no and direction as before, then use Intersect to get the curve.

If you only have an planar outline and you want a spherical outer surface to your panel, make a second sphere centred on the same point as the first, with the radius increased by the panel depth. Place the outline on the sphere where you want it. Then use ExtrudeCrv with Solid=Yes and BothSides=Yes, setting the direction as before to create a solid that penetrates both spheres. Next select your new solid and use BooleanSplit with the two spheres as cutting objects to slice it into three pieces and delete the inner and outer ones, leaving the middle as the panel.


Thanks, but its mapping my curves to this surface which is the problem, I can trim/fin/loft to my hearts conten then.
Unless I misinterperated your post.

Is unrolling and then re rolling the surface the answer? Then I can project straight down onto the former.

It’s more likely I misinterpreted yours :roll_eyes: - If you can post some geometry that shows what you’ve got so far then that would make it easier to help.

No, a sphere isn’t a developable surface so unrolling and rerolling will cause problems.

maybe you can start from a _testQuadSphere
then _Explode, Squish, _FlowAlongSrf:

edit: Alternative: _Cplane _Surface and then draw your geometry as much as possible from the center and then _Pull it towards the sphere:


Thank you for the input all the same :slight_smile:

This is interesting, thank you!

cool, when did this become a testcommand? i still have the original sphere stored from the initial topic where this was initialised, interesting that its now there directly in rhino when you look for it.

Would this be the same for me making a curve network/sweep out of curves extracted from the tuncated hemisphere of the sphere?

please clarify what this refers to.

I have no idea tbh

Another fun one: _testBaseball