[geeks] ahem

[Kurt Huhn]

> Would you care do describe the actual workflow in RealSoft3d, and your
> ideal workflow?
> 

See below...

> See, my ideal work flow for NURBS would be (depending on object being
> modeled) to either start with a primitive shape (like a sphere), then
> add more curves to the areas I want to drag out into more complex
> shapes.  I suspect this is a "bad" way to try to deal with NURBS
> though (most programs make it fairly hard to do it this way).
> 
> My other method for dealing with it was to outline the figure to be
> created, then try to loft surfaces out of the outlines.

That's somewhat similar to what I do.  I prefer to start with primitives
and add curves and surfaces, and subtract other solids using boolean
operations, until I get the shape I like.  I also like to extrude and
loft NURBS outlines into surfaces and solid objects.  I dislike patch
modeling, but that may just because I never really learned how to
properly do it.  I like to "add and subtract" to create objects -
simulating what might happend in a metal or wood fabrication shop.

Rhino, since it was developed for CAD/CAE/CAM environments is extremely
well suited to this type of work.


> 
> I seem to remeber that taking splines and creating surfaces from them
> via lofts, blends, trims, etc, was the Rhino prefered way of doing things.
> But really, the complexity issues always got to me (to add localized
> complexity, like to a facial feature, you must raise complexity of the
> entire model, etc,etc,etc).  Of course, theoretically, you are
> supposed to deal with by splitting your figure into multiple models,
> but then, making it look like one model again is non-trivial.

Rhino isnt' very good at subdivision modeling - well, I suppose it could
be, but that's really not it's intended purpose.  It is possible to add
points and vertices to existing NURBS surfaces, but that type of
modeling is, IMO, better suited to subdivision surfaces anyway.

> 
> NURBS were always really good to me for objects that were simple lofts
> though.
> 
> On a note related to not just using them in a cad/modelling program,
> of all the manners for curved surfaces I've looked at mathematically,
> from implicit surfaces, CSG, subdivision, bezier patches, and more
> that are uncommon, NURBS are the hardest and most complicated to
> grok.  Heck, in my experience in 2D curves, B-Splines (rational or
> not, uniform or not) are just about the hardest to deal with (though
> that may be a matter of bad presentation from professors).

Lack of proper instruction is one reason why I can't work with patch or
subdivision modeling.  Some practice, however, may solve that if I ever
hae the patience to stick with it.

> 
> Subdivision surfaces are also pretty tricky, but thankfully, the tools
> for working on them are virtually the same as for working on polygons.
> I'm still trying to find an easy explaination of the math behind
> subdividing.  So far, it seems one key point is to store models in
> winged edge trees instead of vertex lists.

<homer>
...
</homer>

-- 
Kurt
kurt at k-huhn.com