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brandgw  
#1 Posted : Monday, August 6, 2012 4:12:24 PM(UTC)
brandgw

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I thought ViaCAD was better than this. I used to see this in TurboCAD when I lofted surfaces using with an unequal number of control points. Any suggestion? This is a skinned surface. I also noticed that the skin surface does not align through the control curves. Are there any advanced skin options that I could incorporate?

[ATTACH]4485[/ATTACH]

I will be trying a net-surface next.
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Tim Olson  
#2 Posted : Monday, August 6, 2012 4:29:36 PM(UTC)
Tim Olson

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>>when I lofted surfaces using with an unequal number of control points. Any suggestion?

The number of control points (or curve type) should not matter as the skinning algorithm is driven by the curvature. The resulting skin surface fits the profiles within a tolerance.

>>I also noticed that the skin surface does not align through the control >>curves.

You might be seeing a display resolution issue. If you post the file, I could look further.

Something I find useful when looking at a surface for smoothness is to turn on the isolines under Edit:Resolution.

Tim
Tim Olson
IMSI Design/Encore
brandgw  
#3 Posted : Tuesday, August 7, 2012 10:08:39 PM(UTC)
brandgw

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Tim,
Here is the file. I did a couple of hull skins. One using the green splines and one using the blue splines. Each exhibits roughness in different ways. I could not find your isolines.

I am also trying to work a net surface. I have not had luck with this either. I can get a partial surface using the lower 5, 6, or 7 splines and a similar amount or the forward splines. See the net surface hull layer. When I try to utilize the whole net. I get a bad net mapping curve error. Close examination of the partial skin at the bow shows some serious wrinkles there.

Hopefully you can enlighten me.
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zumer  
#4 Posted : Wednesday, August 8, 2012 6:40:20 AM(UTC)
zumer

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Some of your curves invert, where the control point frame crosses the curve itself twice. That detracts from smoothness.
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brandgw  
#5 Posted : Wednesday, August 8, 2012 11:56:57 AM(UTC)
brandgw

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Good catch. I will have to examine my splines. I developed my splines very simplistically by selecting verticies from a control mesh that defines my hull. You can see it on the hull mesh layer.
ZeroLengthCurve  
#6 Posted : Thursday, August 9, 2012 3:47:39 AM(UTC)
ZeroLengthCurve

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Brandgw,

Although the number of control points doesn't matter in ViaCAD, if you later need to export those curves as importable dxf or similar, those other programs will balk or crash or produce horrid surfaces. But, so long as your work in VC/VCP is not going into other products, It may not matter. And, since no APIs or XML/other interfaces will let nautical programs and VC/VCP/Shark interoperate/intercommunicate live, it may not matter.



In my case, however, I still follow the nautical designers rule of thumb or experence in that the control points count must equal those of fore and abaft stations. If I do that, then I expect my material weights to be closer matching.

Again, it may not matter, ultimately. Someone building your boat may manufacture it slightly deviating from your plan if they can find things needing improvement.

But, I'm now feeling an urge to revisit stations having difffering control point counts.
brandgw  
#7 Posted : Friday, August 10, 2012 4:15:13 AM(UTC)
brandgw

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ZLC,

Whats's your poison for hull creation. Skin? Net-Surface? Something with splines. What kind of curve? Control point? B-Spline? Interpolate?

Curious what works for you.
ZeroLengthCurve  
#8 Posted : Saturday, October 27, 2012 5:27:27 PM(UTC)
ZeroLengthCurve

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Sorry Brandgw, it has been too many months without replying to you.

The shortish version:

... Refine the hull as far as you can in Freship, if that is still what you are using

... Change precision to high a

... Export export the model as dxf 3d polylines

... Import to viacad

... Isolate the various layers and entities to make things easy to find and manipulate

... In viacad, turn off edges, buttocks, and waterlines layers in the imported dxf

... Convert the stations to interpolated splines

Personally, i prefer interpolated splines over regular polylines or lines. For the hull sideshell, making a skin sometimes takes a split second whereas some surfaces generated strictly from curves/lines cost me 10 to 25 seconds.

In some cases, interpolated splines will curl or change the shape of a curve, especially in the keel if you joined curves. Visually inspect each join.

I now am swinging in the direction of making a hll in freeship of one piece with no creases and abandoning any hope of using meshes or of ever expecting viacad to nativelynjust convert the. No matter what i do, my vcp surfaces never, EVER track or follow the meshes. So, still, my surfaces and solids look beat up, and if ever i tried to use them in renderings, i would be laughed out of a room. I could cheat and use the imported meshes for visuals, but i cannot cut or limit any geometry with them.

Someone sent me an email about a non-commercial utility, but i cannot find the email now....

However, other than a few crashes here and therw, lately i have been feelng more productive with vcp.

As for making shell plating involving areas of high and compound curvature, add more intermediate stations (as tight or as close together as feasible) in freeship and import them into your vcp or viacad model or file. With exranstations, you can deal with the unfortunate absence of curve continuity a transition at the stem, depending on whether you have creases, wateelines, etc. in the model.

As for internal decks or the like, in viacad, set per-compartment waterlines and project those against the sideshell inside, from midplane. Use a waterline upper and lower part to set plate thickness. Creats a skin surface between thentwo. Projectoutboard from centerline a line that goes beyond the sideshell. That line will be for the direction/vector when you use the one solids tool to create a solid that becomes the deck. Make sure the upper and lower curves fit within the compartment, and make sure the outboard line goes beyond the surface or solid the deck will terminate against.

For stringers, do similarly. You may want to explore creatine waterlines in freeship, exporting them to dxf, and experimenting in vcp/vc.

Zlc
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