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Complex shapes are still complex (#478)
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jlm  
#1 Posted : Saturday, August 11, 2007 10:44:24 PM(UTC)
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Hi from Pingyao (China),

Even with the new tools, it is still difficult to make an exact bulged surface (or solid) without bumps.
The attached wireframe is showing the shape that I EXACTLY want to get.

I tried all the surface and all the solid tools with all the options that I could think of.
Maybe I missed something easy, it is still what I hope after many hours of struggle.
Is anybody able to show me the Tao way to success ?

Thanks in advance,

JL
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jlm  
#2 Posted : Tuesday, August 14, 2007 4:58:12 PM(UTC)
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This type of shape is essential in product design.
It is an injection mold core, and I cannot accept a camel back bumpy shape, or assymetric facetted approximation.
I need a surface that fits all the splines, with continuous curvature, exactly what a net surface should be doing.
Anybody help ?
Thanks,
JL
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Tem  
#3 Posted : Wednesday, August 15, 2007 12:53:57 PM(UTC)
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Here is a technique that mike work, sorry I don't have the time to try it.

Divide the curves where they intersect.
Create 4 sided surfaces using the curves.
Join these new surfaces together along edges.
You might need use the Match Surface tool to adjust tangency.
Then stitch all together into a solid.
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giulioandrea  
#4 Posted : Wednesday, August 15, 2007 4:02:38 PM(UTC)
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JL,
I am sorry to say but your network is a little messy... in fact few end points are not quite coincident. This inevitably gives odd results.
Software is not to be blamed here.

I took the license to adjust your network and try myself. All fine here.
The only trick which may be a little unusual is to add two points to the extreme of the network as the first and last section.

Ciao,
G.


PS I suppose you can adjust the surface I enclose by changing tangency to the curves to match your original design.
[ATTACH]121[/ATTACH]...
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jol  
#5 Posted : Thursday, August 16, 2007 7:48:10 AM(UTC)
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Agree .. some shapes are really hard to achieve

I thought this would certainly work with the net surf tool (by placing points at the converging ends .. but I got the old "Us & Vs are in the same or opposite directions" .. whatever the hell that means

My only other suggestion is to try making it as a whole and splitting it !?
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jlm  
#6 Posted : Thursday, August 16, 2007 7:16:21 PM(UTC)
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Tem wrote:
Divide the curves where they intersect.
Create 4 sided surfaces using the curves.
Join these new surfaces together along edges.
You might need use the Match Surface tool to adjust tangency.
Then stitch all together into a solid.


Thanks Tem,
I like this simple method.
Unfortunately in this case I can't match tangencies and when I finally stitch, I get a bumpy assymetric solid.
JL
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jlm  
#7 Posted : Thursday, August 16, 2007 7:23:02 PM(UTC)
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jol wrote:
I thought this would certainly work with the net surf tool (by placing points at the converging ends .. but I got the old "Us & Vs are in the same or opposite directions" .. whatever the hell that means

Dear Jol,
I share your preference for the net surface and I get the same message.
Us & Vs are stupid animals lacking directions.

jol wrote:
My only other suggestion is to try making it as a whole and splitting it !?

?? can you explain a bit more ?
I tried to assemble a set of split ellipsoids, but I could never get good tangencies.

JL
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jol  
#8 Posted : Tuesday, August 21, 2007 11:39:50 AM(UTC)
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Hi JL

Here's my best shot

Tim, you should look at JL's conundrum as it typifies many CU surfacing problems
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giulioandrea  
#9 Posted : Wednesday, August 22, 2007 10:49:09 AM(UTC)
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here is mine :-)
actually I could not get a perfect curvature...
g.
[ATTACH]123[/ATTACH]
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Tem  
#10 Posted : Thursday, August 23, 2007 4:24:33 PM(UTC)
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When examining the curves, I noticed that several of them did not intersect.
I tried making the intersect. That seemed to help a little. I tried to make several smaller surfaces into the shape that I think you wanted, but never found an acceptable result. I even tried deforming a sphere and an elipsoid, then manually pushing and pulling control points on the surface, but found that to be impractical. I might try one more approach. Otherwise I hope you have found the solution and can share it with us forum slackers.
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Tem  
#11 Posted : Thursday, August 23, 2007 4:57:36 PM(UTC)
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I was a ble to get something close but not exactly what I think you intended.
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jlm  
#12 Posted : Friday, August 24, 2007 3:40:40 AM(UTC)
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jol wrote:
Hi JL
Here's my best shot


Thank you Jol,
Unfortunately, your attached file doesn't work on my Mac.
The message appearing twice before opening is "attempt to fit curve to zero or one point".
Then I get 2 "surface-faces", one "surface-match" and big gaps.
JL
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jlm  
#13 Posted : Friday, August 24, 2007 3:43:54 AM(UTC)
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giulioandrea wrote:
here is mine :-)
actually I could not get a perfect curvature...
g.
[ATTACH]123[/ATTACH]


Thank you Giulio,
It's interesting that you managed to get a nice net surface by redrawing new curves.
Though, as you say, curvature isn' perfect...
JL
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jlm  
#14 Posted : Friday, August 24, 2007 3:58:56 AM(UTC)
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Tem wrote:
I was a ble to get something close but not exactly what I think you intended.

Thank you Tem, it is actually very close, but still the following issues :

- it isn't completely symmetric (on another project I built the solid, cut in half, and stuck the same part both sides...) On this one it has to be perfect.

- It is impossible to close the base with a cover surface because of gaps.

- After joining the surfaces "Gap detected in curves. Fix the gaps and try again."

Tim, please tell us how to fix an invisible gap...

JL
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jlm  
#15 Posted : Friday, August 24, 2007 4:17:00 AM(UTC)
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Today, I still have no solution to make a smooth solid following exactly the curves & I must rely on my Chinese supplier's pro-Ing...

Tim, what is your feeling ?
Thanks,
JL
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jol  
#16 Posted : Friday, August 24, 2007 5:02:55 AM(UTC)
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JL

Yes .. it seems to have developed a problem. It does finally reopen for me however .. and you would need to rebuild the net surface as that has mysteriously shrunk

It's otherwise pretty good tho

Tim .. this file's stuffed up on 2 counts .. errors on opening and the net surface has shrunk to an offset of itself .. if you have a chance, can you take a look

We need to fins a solution for problems like JL's .. I can't help but think if we understood what this 'U's and V's in same or opposite direction' garbage was about .. it may be much easier to create many difficult surfaces
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Tem  
#17 Posted : Friday, August 24, 2007 10:29:57 PM(UTC)
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I think that it is a basic technology problem. NURBS surfaces are made of 4 curves (lines) that intersect or terminate on each other. This is why surfaces created from 3 curves are almost always an issue, unless they are planer. As we can see, the ends / end caps of the form that we are trying to make are the big problem. The middle section is easy to create, it is 4 curves, but has some additional influential curves inside, like the U's or V's already existing in a NURBS surface. I could try to make this in another program but it is only a Beta version that runs on the Mac.

Jol: Maybe, I should .zip my files more often before internetting them so they don't get mulched along the way. SORRY!:o
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Tem  
#18 Posted : Friday, August 24, 2007 10:35:33 PM(UTC)
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JL-

I am often frustrated by invisible gaps. I have found no way to solve this issue accept to closely examine where each end point terminates at another curves endpoint. Sometimes, they do not intersect, so one must drive the geometry numerically. I am still learning CU. I wish that I could be of more assistance.
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jol  
#19 Posted : Tuesday, June 3, 2008 2:29:23 PM(UTC)
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Symmetrical Splines .. Tim can we get them into the schedule with some kind of priority ?

All agree say 'aye'
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Steve.M  
#20 Posted : Wednesday, July 2, 2008 5:27:00 AM(UTC)
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Hello all,

I have been looking at the various versions, still trying to make my mind up which version to purchase.

I too have seen some strange popups when attempting net surfaces etc but have now started to get an idea on what is happening.

I realize this is quite an old thread, but anyway, I had a play with the network of curves originally posted, and did produce a G2 surface (after a small edit and adding points to the end of the network.

I am still looking at the surfacing, so will probably be posting question.

Regards
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