I was wondering if there was a better / faster way to skin these curves (layer geometry) than the way I did it. I tried several times to use the skin with guide option but, every time a non acceptable surface was made. Thanks for any advice......
Patrick

Hi Patrick,

I'll be honest, so far the surface tools in VC have confused me, I think this is more down to me lack of using them. I see your method works ok but rather a lengthy process. In Rhino this is called a Network surface and I used your 5 curves to create the surface attached (brought into VC) the surface took 10secs to make ;)

Im about to download Shark and start testing so I would be most interested to see if you can build it in the same way & speed as Rhino....someone kindly put up an avi?? :D

Below is a quicktime movie showing the dome surface created using a couple of surface types.


Net Surface (ViaCAD 2D/3D +)
--Add a point entity to the top and duplicate one of the arc cross sections to close.

Skin with Guide (ViaCAD Pro +)
--Add a point entity to the the top

Cover with Guide (Shark +)
Note isolines, not a degenerative surface as other types.


http://www.csi-concepts.com/Demo/videos/dome.mov



Tim

Tim,
Thank you so much for the video - it really explains alot !!!
Patrick

>>it looks to me that it means that a number of u or v control points are >>coincident in space. Is it that simple?

Yup that's it!


Tim

I also at first thought it was my lack of knowledge in the correct use of the surfacing tools, but the mov posted by Tim as shown I was using the tools correctly and it is just the output surfaces that are quite unexpected.

Looking at the examples:

Net surface. That produced a surface that was pinched at the join of the added curve pic 01 shows the surface in shark using zebra, the loss of tangency clearly shows.

Skin with guides: I currently have the shark demo version 5.5 build 823 for checking the surface tools, but cannot build the surface as shown. I am given an "Acis error" of "Net curves Intersections are not monotonic" (see pic 02)

Cover with Guide. The results where rather strange. Although the surface had continuity it was in ripples over the surface. I have attached a screen grab pic 03, but it does not really show how rippled the surface actually is.


I do use Rhino a lot for producing surfaces so ran a "surface from network of curves" and produced an acceptable result on first attempt, which I imported into shark for comparison. (pic 04)

Hi Tim.

Nice one.

By default Rhino will attempt to sort the curve order, it does work well most of the time, but sometimes Rhino will not be able to sort and will ask for manual input for the UxV curves.

No, I joined the 2 open curves and split the closed curve into 4 for the network (see pic).

The splitting of the closed curve was what I was originally doing in VC/Shark when I first started using the surfacing tools for that kind of surface, but always got the error "Surface U and V are in the same or opposite direction"


Regards,

- Steve

Hi Patrick,



There is no "skin with guide" option in VC, so I am not sure as to what tool you where attempting to use. The surface you posted, did you produce that in VC? If so by which method. I have looked at this but have not been able to produce a single surface that I find acceptable. I can split the surface construction up into a quad and skin, which surprisingly, does give good results (certainly not a method I would attempt in Rhino), so I am interested in your comstruction method.

Regards,

- Steve

There is no "skin with guide" option in VC, so I am not sure as to what tool you where attempting to use. The surface you posted, did you produce that in VC? If so by which method. I have looked at this but have not been able to produce a single surface that I find acceptable. I can split the surface construction up into a quad and skin, which surprisingly, does give good results (certainly not a method I would attempt in Rhino), so I am interested in your comstruction method.

Regards,

- Steve


Steve,
sorry I took so long to respond to your question about how I constructed the skinned surface I posted. Yes I used ViaCad Pro to make it. I experimented first by drawing a 2 inch diameter circle and making a 1 inch arc to the top. Instead of using a rotational surface (which is easy) I knew I needed to use a skin to a point because of the dome shape. I needed to know how many cross sectional profiles I needed to make an accurate skin and then it dawned on me: change the 1 inch arc to an interpolated spine then turn on control points and put a circle at each control point level. It works perfectly but, in order to describe a half circle you need ten descending profiles - alot of work!! On the dome I took the largest arc and converted it into an interpolated spine and used its control point "levels" on all the other arcs. I scaled ellipses to fit the points and then skinned them. If you look at my original drawing on here and turn on all the layers you will see what I mean.....
Patrick