Hi Shaun,

> I'm looking for more flexible solid modeling of organic shapes in general.

Organic shape modeling is not a strong area of solid modeling - solid modeling excels more in semi-mechanical man made type shapes where the shapes are driven more by 2D profiles and have pieces cut out from them.

If you want to make organic shapes, sub-d modeling is overall much more suited for that.

At the same time sub-d modeling is poor in doing mechanical shapes with cut out parts on them.

Different kinds of 3D modeling technology have different strengths and weaknesses, and your best bet in general is to try and leverage each technology in its strong area, rather than trying to do everything in one single tool. Try to use the best tool for each particular kind of a job rather than using a tool that is not well suited for your particular job at hand.


> I would have to re draw all those curve separately and make
> new lofts (or networks or what ever) all over again.

Usually that doesn't actually take much time though - one of the good parts about NURBS modeling is that you can make a lot of stuff happen from a relatively small number of curves and it is quick to draw curves. So recreating some area of your model is usually not so labor intensive in NURBS modeling as it would be in polygon modeling where are dealing with a lot more little elements since you are dealing with individual vertices on the 3D shape directly.


> I would much rather be able to grab the common point and drag
> it so it stretched all the surfaces of the dome at once. Less planning
> ahead, more sculpting like.

Sub-d modeling works exactly like that, so if that's the kind of technique that is important to you, you probably want to be using a sub-d modeler that is based on that technique instead of MoI.


> None of this should be taken as criticism of MOI.

None taken - in fact I want to be very clear that MoI is not really intended to be a replacement for sub-d modeling techniques. If you need to use those techniques there are already a lot of sub-d modeling programs out there that you can use already to do that.

MoI is focused on different techniques than that, but that's actually why it is so useful as a companion program - because the techniques that you can use with MoI are very strong in modeling mechanical shapes, exactly where sub-d modeling is very weak.


> One question I have is, why isn't there a form of cage modeling
> for solids?

It's because of how trimmed surfaces work - after you do some booleans, the edges that you end up with do not necessarily correspond to the control points of the underlying surfaces anymore - the edges are more like markers that mark regions of the surface as holes. Because they're just markers and don't drive the shape of the surface, you can't pull an edge to deform things, the thing that you can pull are the control points of the underlying surface.

You can see those control points on a solid by using Edit > Separate - you can always turn on control points for an individual surface. But because you can't edit a surface by pulling on a trim curve where 2 trimmed surfaces are touching, if you pull the underlying surface control points you will usually open up a gap between what used to be a joined edge on the solid.

For more information, please see this FAQ:
http://moi3d.com/wiki/FAQ#Q:_Why_does_show_points_work_for_some_objects_but_not_others.3F

That has a bunch of illustrations that should help explain why a solid made up of trimmed surfaces is not easily smooshed around by point editing.

Also some previous discussion and explanation here:

http://moi3d.com/forum/index.php?webtag=MOI&msg=4052.6
http://moi3d.com/forum/index.php?webtag=MOI&msg=4050.3

 

> If you do a Show Points on a sphere in MOI something very
> similar to a control cage appears where you get the elastic type
> of modeling I'm looking for. I want to be able to grab a section
> of this cage and extrude it, or weld two points together.

Those are techniques that you'd use in a sub-d modeling program - if that's the style of modeling that you want to do, then you should use a sub-d program to do it - they work exactly like you're describing!

MoI is focused on a much different way of working that than - I kind of describe the sub-d way as more like sculpting where you're manipulating the 3D point cage, and MoI's method is more like drawing where you focus on drawing curves to use either for building shapes or for cutting away areas of your model.

Organic shapes tend to work well with the sculpting method, and mechanical man-made shapes tend to work well with MoI's "construction" type approach.


> I know it's really a trimmed surface underneath, not a mesh.
> But there must be some way get closer to sub D techniques.

Not really - the whole mechanism of how trimmed surfaces work is very different from sub-d modeling, since a trimmed edge is a marker that lives on the shape instead of being something that defines the actual surface shape.

In a polygon modeler there are no trims - every edge that you see is also a natural edge of the face and so pulling the edge around is the same thing as pulling the face around.

However, this same mechanism of trimmed edges is exactly why Boolean operations work so much better with NURBS modeling than with polygons - because with NURBS booleans when you intersect objects the underlying surfaces don't change at all and only new trim curves are calculated on the surface. This greatly helps to avoid complexity in the booleaned result. With polygon modeling booleans mean dicing things up into a bazillion little fragmented facet surfaces which is one of the reasons why it doesn't work very well.


So really the main thing is to use the right tool for the right job!

If you want something that works exactly like a sub-d modeler, then you can get that already by just using a sub-d modeler... It's more of a focus for MoI to actually work differently than a sub-d modeler so that it can have strengths in different areas and work better for the right kind of jobs.

- Michael