Loft Control....

I have always wanted, as an option when lofting, to be able to go
"normal to profile" to any of the profiles that I select. Doing it at
the start and end of, is nice, but more times than not when I need it
to look the way I want I have to set up the GC to get what "normal to
profile" could easily do.

Not that I am opposed to GC, but some of the most complex works around
I have come across is getting GC when turning and making complex
geometry.

Am I crazy for wanting this option or does this make sense? Yes I could
loft in sections to get the start and end tangencies as I go, but that
would create a segmented surface body. And you could knit them together
as one surface, but that just doesn't seem as if it is the same as if
it were just one Loft.

 

Having that control would be nice, but your guide curves would still
need to be in order, or else your surface would be subject to
less-than-desirable corrections if it worked at all.

Another option is to use a sweep with lots of guide curves (section
constrained to guide curves w/ pierce constraints). The instantaneous
section of the sweep is always normal to the main guide curve (a.k.a.
"spine" in some programs).

Personally, I prefer to try sweep before loft as the results work
better and are more stable with what I model. It usually only takes
one or two extra guide curves. Learn to use ellipses in simple
sections.

 

If it matters we can use generatrix and directrix for sweep curve and
path or spine respectively.

Another choice would be B spline and C spline lofts where one is "best
fit" and the other must pass through each sweep section exactly.

 

It makes sense to me. But there's a pretty good chance that I am crazy.

This is the work-around that I often use. It's more work, but the part looks
better and seems to be more robust.


Jerry Steiger
Tripod Data Systems
"take the garbage out, dear"