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 From:  JTB
1693.1 
Looks strange...
***Modeling Of Ideas***
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 From:  PaQ
1693.2 In reply to 1693.1 
Well the shell function seems to be a bit limited actually, as I understand it's a complex operation in fact.

I would love to have a look to a more advanced cad software that can handle complex shelling, but
I'm not sure which one I have to try. (need a demo version :))

For your example you will have a better result by sweeping the same curve with 2 circles having 2 different diameters, and then
do a subtractive boolean .

EDITED: 17 Jun 2008 by PAQ

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 From:  jbshorty
1693.3 
Actually i think it's correct! Look carefully at your surface around the top edge. As you examine the top edge, you can see the surface direction is same as what's happening in the Offset. It's just being amplified in the Offset, so you notice it then. I think the original path curve is curved back at the end a little bit. You might try moving or deleting the second to last point in that curve to reduce the bend in that spot before sweeping...

jonah
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 From:  Michael Gibson
1693.4 In reply to 1693.1 
Hi JTB, can you please post a .3dm model file with those curves in it so I can try the shell over here?

But it is not really surprising to me that you would get a strange result with a shell or offset on such a twisty object with tight curvature in it like that.

In general an offset type procedure becomes difficult when you ask for an offset distance that is greater than the curvature of the surface or curve. It creates a kind of bunching in the generated offset, here is an attempt to illustrate that:



Generally to get a nice result for offset, shelling, or fillets, the offset distance/shell thickness/fillet radius that you use should be smaller than the tightest radius of curvature in the curve or surface to avoid that kind of bunching.

Instead of using shell you may get a better result in this case by creating a smaller circle and doing a second extrusion with it. That will not create something with a totally constant thickness, but it will be difficult to create such constant thickness in your shape there due to its bendy-ness anyway.

- Michael
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 From:  Michael Gibson
1693.5 In reply to 1693.2 
Hi PaQ - probably your best bet for a kind of shelling companion program would be ViaCAD or Alibre, because those ones have geometry kernels that have good shelling in them but aren't very expensive.

You would probably get your best possible results by using SolidWorks or Pro/E for example, but you probably don't want to pay $5000 to get that function I would assume?

- Michael
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 From:  PaQ
1693.6 In reply to 1693.5 
arggg $5000 ... I can live without it for now :)

It's just that some weeks ago I tried to create some bottles design, something like the coke model, or any soft drink bottle ... so the outside of the bottle were easy
to create (with many booleans and fillets) ... but it was quite hard to have a good thickness for the inside part. So I was just asking myself what kind of software
they use for this.

I'll have a look to Viacad and Alibre, I'm really in love with nurbs now, so I want to explore and lean them a little more :)
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 From:  Frenchy Pilou (PILOU)
1693.7 In reply to 1693.4 
Can we do think that a concept of "good form" can be given by the nurbs like in the past hull boats drawing were given by flexible battens?
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 From:  jbshorty
1693.8 
Alibre Design Express is free..
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 From:  Michael Gibson
1693.9 In reply to 1693.7 
Hi Pilou,

> Can we do think that a concept of "good form" can be given by
> the nurbs like in the past hull boats drawing were given by
> flexible battens?

I'm sorry not quite sure what you are asking for here Pilou, are you looking for methods to automatically analyze a surface to see if it has a good shape or not?

You might try searching the web for terms like "Surface fairing" to try and find some more information on that.

- Michael
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 From:  DannyT (DANTAS)
1693.10 
This is pretty normal I thought ?
I usually expect this, not only in MoI, so for something like this I would usually model the form longer, shell it then trim off the ends.

Hope this helps
Cheers
~Danny~
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 From:  Frenchy Pilou (PILOU)
1693.11 In reply to 1693.9 
< are you looking for methods to automatically analyze
No no :)
Just in the artistic meaning!
If the fillet or sweep or ...don't work it's "a bad natural form", if yes it's a "good natural form" ;) as Golden Number etc ;)
(out case of impossibilities of course)

EDITED: 17 Jun 2008 by PILOU

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 From:  karter
1693.12 In reply to 1693.6 
Hi PaQ,

I would agree with Michael and suggest you try ViaCAD as your companion with MoI for shelling puposes. This program
uses ACIS kernel as opposed to Solidworks Parasolid....but it seems very good in the test I did. Alternatively, if you are
like me and also use Rhino we should have Shelling in V5...maybe an early beta will do the trick for you.

Good Luck !!

Rgds,
--Paul--

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 From:  Fredrik (FREDRIKW)
1693.13 In reply to 1693.5 
Hi Michael

I've been trying Spaceclaim LTX for Rhino, and find that to work well with shelling and filleting.
Think SC LTX not so expensive, and it takes the 3dm format in directly.

Do you know how SpaceClaim shelling compares to the shelling in programs like SolidWorks?

-Fredrik
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 From:  manz
1693.14 In reply to 1693.12 
Hi Paul,

>>>I would agree with Michael and suggest you try ViaCAD

There is currently an open beta for version 6 ( http://punchcad.com/products/viacad2d3dv6.htm)

>>>Alternatively, if you are like me and also use Rhino we should have Shelling in V5

Have you ever looked at the "power solids/booleans for Rhino" from Npower? http://www.npowersoftware.com/rhino/proverview.htm just curious as that includes shelling



- manz
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 From:  jbshorty
1693.15 
NPower stopped support of their plugin after Rhino 3, so honestly that plugin is probably dead as doornails. As i mentioned earlier, i believe your rail curve has a little bend near the end. But you could also cap that object and then shell it in MoI, removing both end caps during the shell process. I think that would give you a decent shell...

jonah
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 From:  karter
1693.16 In reply to 1693.14 
Hello Steve,

>> Have you ever looked at the "power solids/booleans for Rhino" from Npower?
>> http://www.npowersoftware.com/rhino/proverview.htm just curious as that includes shelling

Yes I did try their plugin in V3 and then their shelling was hopeless !!! but that was before I actually had the need
for offsetting a complex polysurface for our water cooling design....there are so many apps available now with more
control on shelling such as different applying a different thickness to an area but not all...

ViaCAD looks interesting so far ;-)

Rgds,
--Paul--

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 From:  manz
1693.17 In reply to 1693.15 
>>NPower stopped support of their plugin after Rhino 3, so honestly that plugin is probably dead as doornails.

I was just curious. I use Rhino mainly for surfacing and have no need for booleans/shelling. I use other products for that.

>>i believe your rail curve has a little bend near the end.

Well, it is not my rail curve, but as you mention, having the "cap ends" enabled on extrude, then selecting the end caps for shelling would produce better results.


- manz
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 From:  manz
1693.18 In reply to 1693.16 
Hi Paul,

>>ViaCAD looks interesting so far

I have looked at earlier version, but that was quite a while ago, I am currently downloading, but with slow feed from their site, so will take a look later.

I will also have a look at the latest release from Alibre when I have time (I have never used that before).



- manz
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 From:  karter
1693.19 In reply to 1693.18 
Hi Steve,

>> I have looked at earlier version, but that was quite a while ago, I am currently
>> downloading, but with slow feed from their site, so will take a look later.

First impressions are good and I think it would be another good partner for MoI. Nothing
beats MoI for its slick interface and speed of use and it's ability to swap data rapidly with
Rhino is critical for us.....were sold on these two but as far as shelling without spending
££££, ViaCAD looks really cool for that purpose.

Rgds,
--Paul--

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 From:  PaQ
1693.20 In reply to 1693.19 
Hello there,

Well I have done a quick jump into viacad pro demo (15 days trial) ...
I get some trouble to import some 'simple' moi model, but I have to lean it a little bit more I guess.

For the moment it looks like I have to stitch every surface from the object because everything is separate ... and the stitch command return me
error messages ... so I can't really test the shell.
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