Boundary surface question

I make a boundary surface, 2 curves in one dir, 3 in the other. I cut
a section through the resulting surface near one of the curves and
it's nothing like the curve, IOW the surface doesn't go through the
curve like it's supposed to. Anyone know why?

 

No, fwiw. Try projecting the curve normal to surface instead of sectioning
and see how it looks.

 

: I make a boundary surface, 2 curves in one dir, 3 in the other. I cut
: a section through the resulting surface near one of the curves and
: it's nothing like the curve, IOW the surface doesn't go through the
: curve like it's supposed to. Anyone know why?

Try changing the order in which you pick the second direction curves. Pick them in
order, one end to the other. If this is WF, when you've picked the middle one, you
should see a surface form and then continue to the third curve when you've picked
the last one. If you don't pick them in that order it will think you're done when
you get to the end curve and ignore the middle one.

David Janes

 

Thanks David. You have to pick them in order anyway or you get a weird
shape, don't you? Or do you mean 3,2,1 instead of 1,2,3? Tried that
and it makes no diff.

 

: > : I make a boundary surface, 2 curves in one dir, 3 in the other. I cut
: > : a section through the resulting surface near one of the curves and
: > : it's nothing like the curve, IOW the surface doesn't go through the
: > : curve like it's supposed to. Anyone know why?
: >
: > Try changing the order in which you pick the second direction curves. Pick
them in
: > order, one end to the other. If this is WF, when you've picked the middle one,
you
: > should see a surface form and then continue to the third curve when you've
picked
: > the last one. If you don't pick them in that order it will think you're done
when
: > you get to the end curve and ignore the middle one.
: >
: > David Janes
:
: Thanks David. You have to pick them in order anyway or you get a weird
: shape, don't you? Or do you mean 3,2,1 instead of 1,2,3? Tried that
: and it makes no diff.

 

: > : I make a boundary surface, 2 curves in one dir, 3 in the other. I cut
: > : a section through the resulting surface near one of the curves and
: > : it's nothing like the curve, IOW the surface doesn't go through the
: > : curve like it's supposed to. Anyone know why?
: >
: > Try changing the order in which you pick the second direction curves. Pick
them in
: > order, one end to the other. If this is WF, when you've picked the middle one,
you
: > should see a surface form and then continue to the third curve when you've
picked
: > the last one. If you don't pick them in that order it will think you're done
when
: > you get to the end curve and ignore the middle one.
: >
: > David Janes
:
: Thanks David. You have to pick them in order anyway or you get a weird
: shape, don't you? Or do you mean 3,2,1 instead of 1,2,3? Tried that
: and it makes no diff.

I assumed you were on WF or WF2. There they simplified the curve choice and pretty
much eliminated 'Approx' type curves which roughly guided and helped shape
surfaces but didn't exactly match them. If you are using the 3rd, middle curve as
this type of 'Approx' curve, it will never match it exactly and it is not supposed
to.

If it is just three second direction curves then they must all connect with the
first direction curves. So generally you'll have points on the first direction
curves through which your middle curve is constructed. Are we on the same page?
speaking the same language?

David Janes

 

If it is just three second direction curves then
That doesn't seem to be true. The boundary curves must form a closed
boundary but intermediate curves don't have to intersect the boundaries.
The surface will pull away from the intermediate curves to conform to the
boundaries. (This could be something new in WF2. I've never tried it
before.)

I'm sure I don't have a clue what's going on, but if you want to export the
curves and email them to me I'll see if anything rings any bells. (Actually
you might try exporting the curves and creating the blend using them.
Strange things happen.)

 

: On Mon, 12 Jul 2004 14:26:00 -0700, "David Janes"
:
: >
: >: >: >: > : I make a boundary surface, 2 curves in one dir, 3 in the other. I cut
: >: > : a section through the resulting surface near one of the curves and
: >: > : it's nothing like the curve, IOW the surface doesn't go through the
: >: > : curve like it's supposed to. Anyone know why?
: >: >
: >: > Try changing the order in which you pick the second direction curves. Pick
: >them in
: >: > order, one end to the other. If this is WF, when you've picked the middle
one,
: >you
: >: > should see a surface form and then continue to the third curve when you've
: >picked
: >: > the last one. If you don't pick them in that order it will think you're
done
: >when
: >: > you get to the end curve and ignore the middle one.
: >: >
: >: > David Janes
: >:
: >: Thanks David. You have to pick them in order anyway or you get a weird
: >: shape, don't you? Or do you mean 3,2,1 instead of 1,2,3? Tried that
: >: and it makes no diff.
: >
: >I assumed you were on WF or WF2. There they simplified the curve choice and
pretty
: >much eliminated 'Approx' type curves which roughly guided and helped shape
: >surfaces but didn't exactly match them. If you are using the 3rd, middle curve
as
: >this type of 'Approx' curve, it will never match it exactly and it is not
supposed
: >to.
: >
: >If it is just three second direction curves then they must all connect with the
: >first direction curves. So generally you'll have points on the first direction
: >curves through which your middle curve is constructed. Are we on the same page?
: >speaking the same language?
:
: Oui, oui. Yeah, the curve in the 2nd dir was a through (2) points
: curve, and the 2 points lie on the 2 curves in the 1st direction. I
: wasn't using approx surface either, just the regular old boundary
: surface. I've been doing this for years and I always seem to find the
: inexplicable...
:
And try it and wrestle with it and fight it and it just won't work right no matter
what. Then suddenly, for no reason, it does. Well, here's something else you've
probably already thought of, but, for the less experienced in the audience, here
goes: end point tangency of each of those second direction curves should to be set
the same for the curves to 'take'. It most dramatically effects ability to set
higher quality boundary condition on outside boundary curves but I've also had
curves fail just because of that small difference. There's probably a
troubleshooting check list somewhere for boundary blend surfaces because there's
an awful lot like this that can go wrong. I've even taken to building them on
other surfaces, making the curve type 'Quilt/Surface' instead of 'Free'. That
turns those outer boundary curves into COS, capable of supporting a curvature
continuous middle curve. Can't think of anything else at the moment. It'll
probably work at some point and you won't even know why. And you'll be left
thinking 'Well, all of those years of schooling sure paid off.'

 

: > >If it is just three second direction curves then
: > > they must all connect with the first direction curves.
:
: but intermediate curves don't have to intersect the boundaries.

Yes and no. That kind of depends on the version of the software. Before WF, you
had to select, before hand, approximate blend to get the middle curve that didn't
necessarily touch the first direction curves. Then there was another way, within
the curve selection, of 'First dir', Second dir' and 'Approx dir' which seemed to
behave like the approximate blend, enabling selection of non tangent internal
curves. Seems like they started to simplify this after they introduced ISDX and
its easy curve creation methods. However, WF did change the workflow. Before you
pick a couple first direction curves, a couple outet second direction and then the
internal one. WF now is two first, then the remainder second but in order,
straight across. If solvable, the surface previews as you select the second second
direction curve. But if you happened to pick the other outer second direction
curve, you can't go back to the middle one. I think I said this already.

DJ