Create a spere

 From:  Michael Gibson
5296.3 In reply to 5296.1 
Hi jki - the best tool for creating spheres manually is the revolve command. You would create just one vertical arc and then use Revolve to generate a surface of revolution from that - that's how the actual sphere primitive object created by the regular Sphere command is created.

> I used the “Network” function. the second shape is the result, one control point is totally asymmetrically placed. Why?

It's because Network acts kind of like applying a film over the shapes, it has a sort of "tension" in the inner area and does not know about how the shape is supposed to continue on along the outside edges. Because of this it is usually better to use longer curves with using Network instead of trying to do things in little individual cut up pieces at a time.

> Sweep is OK. It creates a symmetrical control point set, and the sphere is smooth. Unfortunately, it creates
> a huge amount of control points, making the surface practically un-editable

Sweep moves a profile along the paths, and the profile tends to stay more rigid in shape with less soap-bubble-like tension on it as Network uses.

See also this previous discussion:

> Sweep is OK. It creates a symmetrical control point set, and the sphere is smooth. Unfortunately, it
> creates a huge amount of control points, making the surface practically un-editable

You mean you want to do control point editing of the resulting surface? That's actually not really the primary workflow for modeling things in general with MoI - instead of trying to manipulate the surface control points after you have created it, you should instead focus on getting the curves set up how you want them so that after you generate the sweep the surface that is generated from that is in the shape you want already and does not need any further control point editing after that.

If you want to make some kind of small local refinement to a surface using control point editing, then it basically means that you're really using the wrong tool for your particular job - that kind of thing is better suited for a polygon modeling tool rather than MoI, and you will definitely get frustrated if you try to apply polygon modeling techniques inside of MoI, MoI is not focused on that kind of workflow, MoI is focused more on a "draw curves and construction" type workflow. If that type of workflow does not fit what you need to do then it probably means that MoI as a whole does not really fit with what you need to do.

> Quite near the victory I tried to use sweep for 3 free curves. And again: this does not work, system creates a strange artefact on top.

When you're trying to sweep along one rail, the profiles are moved along the rail keeping them perpendicular to the rail. That produces a kind of effect like you are showing there - try doing an "Array along curve" of the shape along that bottom rail and you will see a similar thing - since each profile is being kept perpendicular to the rail as it moves along it that causes the end point to swing around as well instead of it staying rooted at that single location.

> Back to my previous post: How to create a smooth surface, with minimum control points controlled by
> 3 different curves, assuming that the surface touching the curve has the same perpendicular as the
> curve in that point.

If you do want to do control point manipulation, do a revolve from either just one vertical curve or a rail revolve with one vertical curve and one bottom one, and that will generate a surface with a sparser control point layout (for Rail revolve you may want to use Rebuild on the curves before generating it).

Otherwise the other main option is to use 2-rail sweep (not 1 rail) and apply your shaping onto your curve framework instead of worrying so much about the control point count in the generated surface.

Also just in general if you want to make a sphere like you are showing there is already a sphere tool that makes it easy to generate perfect spheres directly...

But if you are trying to build a sphere with the idea of then mutating it into some other shape, that's a very polygon modeling type of workflow and that's not usually how you should approach models in MoI - instead of generating a different initial shape you should instead make the curve framework have the shape you want so that when you then generate surfaces from those curves the surfaces are in the shape that you want already rather than needing to be mutated from there. If that does not work for your particular kind of shape, it probably means that you would be better off in a different type of modeling system for that particular shape, like for example a polygon modeler instead of MoI.

Hope this helps give you some general advice! I'm not 100% sure what your end result is since you are only talking about making a sphere here, and I assume that you actually want to create something other than a sphere. If by any chance you do want to build a sphere like you are showing then the most simple answer of course is to just use the sphere tool...