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ZeroLengthCurve  
#1 Posted : Monday, June 29, 2009 6:33:54 PM(UTC)
ZeroLengthCurve

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Tim, is there a mathematically feasible way:


-- to decompose a mesh into separate parts at user-defined points, like trimming a solid?

I ask because i imported a mesh of my ship hull (562' long, 70 wide max/66' wide at waterline, and has many curvy areas) and the mesh is fairly beautiful (to me) in Punch! blue, and it is by itself only some 2.9 MB. If VC could draw surfaces at that small size -- surfaces that elevated off the mesh -- that would be ....

F A N T A B U L O U S...

(I've tried converting the mesh, but doing it to solid locked up or was taking so long i killed the process and moved on. I don't want to turn the mesh to curves(?) or other objects just yet.)

So, in a restated sentence, can in the near future VC convert meshes to a skin/surface equivalent? It would take my file size down to 3 MB vs 90MB.

(I created the model in Delftship, then exported the lines to .obj wave front. Imported into VC P v6 patch 838, then modified the axes and marveled at the small file size.)

OR OR OR...

Or, is there a way to stop the selection of the mesh from showing all the vertices and panels/etc as one unit/object? Some other ideas:

-- can it act like a uniform surface and allow snaps (on face/etc)
-- would it be possible to make cutaways into the model, divide/trim it, make transparent areas without necessarily trimming and losing the surface...)

CHEERS!
Tim Olson  
#2 Posted : Tuesday, June 30, 2009 12:48:41 AM(UTC)
Tim Olson

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>>So, in a restated sentence, can in the near future VC convert meshes to >>a skin/surface equivalent? It would take my file size down to 3 MB vs >>90MB.

Anytime we convert from a simple structure like a triangle to ACIS, the file size goes up significantly. Although they are not converted to NURBS (which are even heavier), they are converted to bounded planar analytics which still includes a bunch of topology that adds to the size. What was three vertices defining a simple triangle structure becomes a plane equation bounded by three straight edges where each edge has two vertices.

Tim
Tim Olson
IMSI Design/Encore
nabed  
#3 Posted : Tuesday, June 30, 2009 7:03:02 AM(UTC)
nabed

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I think what ZeroLengthCurve is looking for is a funktion that interpolates a triangulated mesh into one nurbs surface, not several surfaces one for each triangle.
This would be a kind of reverse engineering function (like as far as I know is offered in Rhino, either native or via plug-in I don't remember)

This would be a very handy function to have in a future version.

Ciao, Norbert
Tim Olson  
#4 Posted : Tuesday, June 30, 2009 10:43:30 AM(UTC)
Tim Olson

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Originally Posted by: nabed Go to Quoted Post
I think what ZeroLengthCurve is looking for is a funktion that interpolates a triangulated mesh into one nurbs surface, not several surfaces one for each triangle.
This would be a kind of reverse engineering function (like as far as I know is offered in Rhino, either native or via plug-in I don't remember)

This would be a very handy function to have in a future version.

Ciao, Norbert


Thanks Norbert for the clarification. We did look at that for some work we did with Immersion but found it outside our area of expertise. I believe GeoMagic is a company that specializes in that type of reverse engineering task.

Tim
Tim Olson
IMSI Design/Encore
ZeroLengthCurve  
#5 Posted : Tuesday, June 30, 2009 1:46:47 PM(UTC)
ZeroLengthCurve

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I think i could settle for the meshes facets/faces appearing the way they do when they are selected, but it would be grand (great) if one could "segment" them into arbitrary cuts, say, longitudinally, or from side view, cut them into 5, 10, 15 pieces so the mesh could be on-off layer-managed.

On the other hand, if one could "touch" the side of the mesh so that line trims could be done, it would help avoid redrawing hundreds of surfaces, and would help ensure that items hung on a geometry surface are not floating off in space near but not attached to the hull surface.

On the third (hehehe, third) hand, if external references can be realized, then ... wait, i lost my train of thought... darn...
tmay  
#6 Posted : Tuesday, June 30, 2009 2:04:05 PM(UTC)
tmay

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http://www.tsplines.com/

ttrw (and others) were talking about this last year on the forum.

The benefits of subdivision modeling with precise conversion to NURB surfaces.

Unfortunately, only available as plugin for Rhino or Maya, and not cheap.

tom
ZeroLengthCurve  
#7 Posted : Tuesday, June 30, 2009 3:35:04 PM(UTC)
ZeroLengthCurve

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Thanks.

I guess it's possible that even tho this is outside of Punch!'s expertise, it's possible that some company may cry patent infringement/violation. I hope Punch! can find a way to get around any such patent and make use of the fact that if VC/P can import the mesh, maybe it can eventually be found how to reduce the file size... (Wishful thinking on my part)...
ZeroLengthCurve  
#8 Posted : Tuesday, June 30, 2009 6:18:37 PM(UTC)
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Say, Tom/Tim,

I'm not on my laptop so i have to try later to find out whether or not i can change the iso u/v on the .obj wavefront mesh i imported into VC. I am pretty sure i recall not finding a way to trim and i don't think i tried to thicken the mesh, either. But someone told me:

--

"To me, there is no difference between a mesh and a surface. In a surface you will see lines inside called isolines. This is nothing more than a 2D mesh. 3D meshing is still a surface with points that can lie above or below a set plane. The mesh/surface has no real thickness but can have it assigned as a property. In Rhino a hull is one surface."

--

But, is there a way to so a Surface/Mesh Intersect? For doing the plan views of the decks and generating boundaries to the , it would be nice. I will try again to see if SSI works. That could prove quite useful to me.
zumer  
#9 Posted : Thursday, July 2, 2009 6:29:37 PM(UTC)
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If you're working with windows, Marcus Bole's PolyCAD will convert a mesh into a nurbs surface, or vice versa, using the vertices of the mesh as control points of the surface. You can define U or V rows as knuckle points for edges, and knock out U & V rows, to reduce the file overhead. IGES is the logical transfer format between the two programs for a surface, dxf for mesh. Convert a mesh into a solid (even if it's a zero-thickness faceted sheet solid) and they'll intersect/interact in VC. You can raise the order of the surface for smoothness, and subdivide at will, subdivide or decimate meshes. Marcus' code is in some of the big ship design programs, parametric single surface hulls, compartments, offsets, hydrostatics. His most recent version even does ACIS surfaces, but it's still shaky. He's a maritime guy.
ZeroLengthCurve  
#10 Posted : Saturday, July 4, 2009 1:48:03 PM(UTC)
ZeroLengthCurve

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zumer, THANKS for reminding me... i have so many things going on that i had forgotten to pursue that avenue...
Steve.M  
#11 Posted : Saturday, July 4, 2009 2:06:44 PM(UTC)
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Originally Posted by: zumer Go to Quoted Post
Marcus Bole's PolyCAD


I had forgotten about that. I did download some time(versions) ago but , well, forgot and did not take time to look. I will have a play (if I remember :D,... I used to make a note so I would not forget, unfortunately these days, I usually forget where I put the note :D)
ZeroLengthCurve  
#12 Posted : Friday, July 10, 2009 4:03:02 PM(UTC)
ZeroLengthCurve

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Zumer,

I checked out PolyCAD, but i felt intimidated. For the life of me i just simply could not figure out how to get a surface drawn. I thought Rhino 3.x was intimidating, but picked it up in a few hours.

As for my kvetching/lamenting over meshes and my inability to use a mesh as a cutting surface, i just successfully got to manipulate the mesh into faces/surfaces and join together several faces at a time. I exported from DelftShip the hull as .stl, then before mirroring the starboard side (and possibly doubling the size to some 6 or 8 MB), i decided to draw in a surface as a representative deck. I switched the view to a right side view and windowed a few surfaces/faces at a time to be joined. Then, i took the surface break/split tool and successfully trimmed the "deck" to two pieces, changed colors and visually looked it over for any jaggies i might not want. Even if i found any, they seem very small considering the scale/size of my ship. Now, i have a way to move forward.

Also, after doing this exercise, i realised that i must further smoothen my hull back in DelfShip before bringing it to ViaCAD. If i had DelftShip Pro, the automated line/point fairing would be IMMENSELY valuable in pre-export work.

However, i think i need to revisit my steps to find out if it mattered what kind of mesh i made. The one i thought that i could not trim/successfully break down may have been because i started it out from the .iges model. Or, maybe because it was both sides of the hull as one selectable mesh and maybe geometrically compounded the CPU/RAM problems that made me give up after 5 or so minutes (to where VCP and VC just "not respond") and kill the VCP process. Being able to turn on points in the mesh/subsequent surface geometry could be useful in that for local issues of outward bulging i can move the point to an acceptable coordinate.
zumer  
#13 Posted : Saturday, July 11, 2009 10:44:51 AM(UTC)
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IGES has provision for meshes, but I've never found transfer to be as good as .dxf. However, dxf has a limitation on points in mesh entities, I think around 35 thousand points. IGES does smooth surfaces, though, which .dxf doesn't. Smoothing/fairing would be nice. Here's something I've been having to smoothe iteratively, which was easiest in PolyCAD. The segment being edited LH top has been copied and radially arrayed, the yellow side is mesh, the other has been converted to NURBS surfaces that're displaying zebra, Gaussian curvature and mean curvature. Time to learn and practise is all it takes. I've been using PolyCAD for five or so years. I'm much more competent with it than VC.
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ZeroLengthCurve  
#14 Posted : Sunday, July 12, 2009 1:37:41 AM(UTC)
ZeroLengthCurve

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Zumer,

Thanks! Saturday i spent some time paying closer attention to my model in the mesh form. I noticed that lots of circular patterns in the mesh could be cleaned up so they are more grid like. Tho VC & Delftship are not interactive between each other (unless the products' companies mutually wrote scripts to enbable things like Rhino and another app maker do...), it is easy enough to periodically dump updated .obj files and look at them in VCP. This is actually a good exercise for me as it even more forces me to pay more attention to detail and not just presume that DelftShip (with or without automated fairing, but particularly the free version i'm using, since it lacks automated line and point fairing) will have nicely faired lines.

So, due to selecting the mesh in VCP and inspecting the curves in the mesh, i decided to remove virtually every single point that has no lines attached to it and another point. This alone significantly reduced the number of facets and all frm an original 40,000 something. This should ease the strain on my CPU, i imagine.
Mark  
#15 Posted : Sunday, July 12, 2009 9:11:00 PM(UTC)
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Originally Posted by: zumer Go to Quoted Post
IGES has provision for meshes, but I've never found transfer to be as good as .dxf. However, dxf has a limitation on points in mesh entities, I think around 35 thousand points. IGES does smooth surfaces, though, which .dxf doesn't. Smoothing/fairing would be nice. Here's something I've been having to smoothe iteratively, which was easiest in PolyCAD. The segment being edited LH top has been copied and radially arrayed, the yellow side is mesh, the other has been converted to NURBS surfaces that're displaying zebra, Gaussian curvature and mean curvature. Time to learn and practise is all it takes. I've been using PolyCAD for five or so years. I'm much more competent with it than VC.


Zumer,

Would you post quick tutorial on how to smooth meshes and convert them to NURBS in PolyCAD?
Intel iMac-20,2 | macOS Ventura 13.3.1 | SharkCAD 14 |
ZeroLengthCurve  
#16 Posted : Monday, July 13, 2009 4:41:44 PM(UTC)
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Last night i on a lark decided to revisit dumping a .dxf file out of Delftship. I exported DXF 3D Mesh, and realized right away that i'd forgotten about that option, and spent too much time lamenting the "non-selectability of 3D meshes" imported into ViaCAD (apologies, Tim).

But, it took about 50 meshes-to-(sur)faces just for one side of the model, and i joined enough of them to get it down to around 35 surfaces. Still, the model weighs in at some 35 MB, where a plain mesh from the .obj wavefront file type exported from Delftship is some is under some 6 mb. I suspect it's due to the sheer number of vertices and so on.

So, my plan is to temporarily import the meshes-converted-to-surfaces and use them to trim my decks' surfaces/solids where necessary, then expunge them from the model. (One person told me a drafter modeled an LNG ship over some 800' long, drew details of pipes, ladders, the "No Smoking" billboard, deck/ground tackle, rudders and all, and it was under a few megs. But, it long as heck to actually plot...)

However, as i stated before, this need to break down the meshes taught me a little bit more about ATD (Attention To Detail) and it helped me wipe out an immensely large number of vertices and cut down the file size.

Now, as i told one of my co-workers, "I feel psychologically ready to begin detailing the innards of my model" and stop spending so much time refining the hull.
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