SHELL REBUILD - USING NETWORK CURVES  1-20  21-24

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 From:  AlexPolo
8643.1 
Hi All,
Trying to rebuild this shell surface as a continuous non trimmed surface. I have created a network cage but keep getting failures if someone could point out the issue would be great. I get close to result in Rhino using NETWORK SURF command.

You can download 3dm file from following link its 14meg file.




https://drive.google.com/folderview?id=0BwzK5muLiElSZWtUbXJULTN5blk&usp=sharing

thanks
Alex.
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 From:  Michael Gibson
8643.2 In reply to 8643.1 
Hi Alex, a single untrimmed NURBS surface is defined by a rectangular grid of control points, so it's inherently a 4 sided thing. You can have some of the sides compressed down to a single point but you can't have more than 4 sides, and you have 8 sides here so that's the problem. So it's just not possible to make that shape out of one single untrimmed surface, to have it as a single surface you would need to have some trims on it.

For doing it with Network you'd need to break it up into multiple 4 sided areas.

- Michael
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 From:  AlexPolo
8643.3 
Hi Michael,

Have split into 4 sided sections still cant get it work - worked in RHINO by picking the curves in direction sequence.

Here is split cage only.

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 From:  Michael Gibson
8643.4 In reply to 8643.3 
Hi Alex, there are some little tiny pieces in a few areas:





There are also a few areas where ends don't meet up quite exactly. I've tuned this up in the attached 3DM file by moving the ending control points so the pieces are all trued up. With the attached file you should be able to make a network on each 4 sided area.

This will not make a very smooth result though, particularly at the internal points where 6 edges are coming out from a single point.

Your best bet may be something like make one surface out of something like this:




Then trim off the corners of that and do blends down to the "foot" areas.

- Michael

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 From:  AlexPolo
8643.5 
Hi Michael,

Thanks for the advice - what I am using the shell for is to run a RHINO plugin called ARMADILLO which maps tiles onto the UVs surface and requires a seamless continuous untrimmed surface. Here is the surface I generated in RHINO and the plugin effect over the surface so you can see why the continuity is important.

Also I thought with Network Curves and loose option if points dont exactly meet it does a loose skin.




info on plugin.

http://www.dig.gallery/armadillo
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 From:  Michael Gibson
8643.6 In reply to 8643.5 
Hi Alex, can you post the Rhino surface so I can see how it's configured? Like does it have an internal crease?

re:
> Also I thought with Network Curves and loose option if points dont exactly meet it does a loose skin.

Yes that's true but its also possible for it to interfere with the automatic sorting and distinguishing U and V directions.

- Michael
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 From:  Michael Gibson
8643.7 In reply to 8643.5 
Hi Alex, here's another configuration you might try - here I've sacrificed 4 of the sharp corners and made those areas smooth with little blend curves put in.

You can make a single surface out of it but there will be some stress apparent in the surface in those corner areas.

- Michael

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 From:  AlexPolo
8643.8 
Hi Michael,

Thanks for that the corners did the trick - here is the rhino surface with the sharp corner but the UVs that where generated where good which was the desired final result.

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 From:  Michael Gibson
8643.9 In reply to 8643.8 
Hi Alex, the Rhino Network command has a bug where it just silently ignores internal corners in the input curves and makes an out of tolerance squiggly result in those spots, if you zoom in on this area you can see it:





Although that bug happens to be good for your particular use case right here, it can cause problems if you were intending to join that surface to other pieces like extrusions from those same curves.

- Michael

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 From:  AlexPolo
8643.10 
Hi Michael,

Many thanks for your input - understanding the deeper realms of MOI and curve handling. Again your knowledge is most appreciated.

Look forward to next release.
regards
Alex.
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 From:  Barry-H
8643.11 
Hi Alexpolo,
I have manage to produce a good surface from the curves using the uniform 10 point network.
I started by extending the 4 outer curves to allow for the blend to be trimmed.
To get a smoother fit I added 4 new curves these where produced by projecting onto the surface
produced from original curves ( could have used iso tool ). A small scale adjustment was made to the one curve. Ran network again trimmed off blended feet and also ends.
Would be interested to know how this compares to Rhino surface.
Curve file is attached.
Cheers
Barry



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 From:  AlexPolo
8643.12 
Hi Barry,

Thanks for file - I couldnt Network Surface from geometry supplied maybe if you could just send me the surface only - to give you an idea of the final aim - I am working with another Studio - Studio Kite which have just finished building a large scale 3d delta printer. We are looking at printing textured shells that would form a concrete mould to do spray concrete with. Just as an exercise and a demo of what the technology is capable of.

Here is info on machine

http://www.studiokite.com/3d-printing/#/cooper/

and some concept renders of the proposed structure.











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 From:  Barry-H
8643.13 In reply to 8643.12 
Hi AlexPolo,
when selecting curves for network select in order in one direction then in order the other direction .
So with curves In my file you should have 7 curves in the X and 5 in the Y.(highlighted in previous post photo)
I will post the surface if this doesn’t work for you.
Cheers
Barry
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 From:  AlexPolo
8643.14 
Hi Barry,

Many thanks that actually worked great - thanks for your input.

Will keep posts as project progresses.

all the best

Alex.
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 From:  Michael Gibson
8643.15 In reply to 8643.14 
Hi Alex,

> Will keep posts as project progresses.

Please do - looks like an interesting project!

- Michael
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 From:  XNurbs
8643.16 In reply to 8643.14 
Hi Alexpolo,

The surface generated by RHINO plugin ARMADILLO is quite poor (RHINO.png). It uses a low-end lofting method.



The following image (XNurbs.png) shows the good surface and the video (http://www.xnurbs.com/download/XNurbs.mp4) demonstrates how it can be done. (No need any tricks you know – just select the curves and it will produce Class-A surface for you).



Could you send me the network cage (i.e., the original curves) in the STEP, IGES and SAT formats? Just keep the little tiny gaps as they are. (I cannot find any curves when opening your 3dm file in SolidWorks). I will then send the generated surface back to you during the weekend.

Kevin

EDITED: 25 Oct by XNURBS

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 From:  AlexPolo
8643.17 
Hi Kevin,

Had a look at the Xnurbs site product looks good. Please find shell wireframe geometry.

Thanks for your input.
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 From:  XNurbs
8643.18 In reply to 8643.17 
Hi AlexPolo,

The attachments are the generated surface (XNurbsSurf.IGS and XNurbsSurf.stp), and XNurbsZebra.png show the zebra image of the generated surface.



Need to point out that the curve file you sent contains some bizarre curves as showing in the following image. They are obviously overlapped; I don’t understand why these weird curves are there? A mistake? So I delete them. The remaining curves also have small overlaps – they have a negative impact to the final surface quality (I did not make any correction to those overlaps). If you cannot make the curves connected with each other, then you should keep them open (i.e., leave a big gap). This way you will get a much better surface.



Kevin

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 From:  AlexPolo
8643.19 
Hi Kevin,

Thanks for the model - the continuity is very good but unfortunately it produces a trimmed surface from which the UVs are very messy to try and get regular UV network going for panelling work. Have a look at the point surface difference between the models. I am also a SOLIDWORKS user how much does the plug in cost - no mention on website.






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 From:  XNurbs
8643.20 In reply to 8643.19 
Hi AlexPolo,

Of course, it is a trimmed surface. The following is a screenshot inside SolidWorks – simply select the curves and it takes a couple of minutes to complete the design.



I am confused why you need to manipulate the control points – the “regular UV network” you mentioned is actually the control points, and manipulating these control points is time-consuming and boring work. You may never get the good positions for those control points. You should NOT waste your time on them. Instead, you should focus on designing the curves or constraints, i.e., modifying or adding curves or constraints, and let the software generate the smoothest surface from your constraints.

As Michael Gibson already said “it's just not possible to make that shape out of one single untrimmed surface”. Using one single untrimmed surface is a low-end method, and the surface quality will definitely be poor. The UV network generated by XNurbs is much better than yours – there is no sharp turning and they moves smoothly.

I need to remind you again that your curves used for generating XNurbs surf are not good, and have a very negative impact to the surface quality (I did not make any correction to your curves). You need focus on designing the “good” curves or constraints, and let the software generate the smoothest surface from your constraints.

Next week, you should be able to find the complete info, e.g., pricing, from our website.

Could you tell me which software you use to show the control points?

Kevin
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