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Irregular Lofting on a Boat Hull
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* January 24, 2019, 08:05:23 PM
Cant work out why this profie an has irregular loft from the top to bottom side (black visible) when draft rendered in world plan.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


January 24, 2019, 08:43:49 PM
#1
In the past when I have had similar problems, I find that it is usually operator error on my part. I think when I moved the profile I positioned or snapped it to the wrong spot. If I go back and look at all the different views I can usually find something that isn't aligned correctly either it is offset to one side or the other or the angle of the profile has changed.
Paul

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* January 24, 2019, 08:55:27 PM
#2
Paul thanks I will check the alignment again.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 24, 2019, 09:05:58 PM
#3
It's likely a rendering artefact, not a geometry flaw.  Offset lights or similar.  Passing sections through the hull and mirroring them across the centreline will determine if there's a real thing happening. 

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* January 24, 2019, 10:35:08 PM
#4
Murray I think you may have hit the nail on the head. That makes sense, thanks mate.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 25, 2019, 02:19:09 AM
#5
Actually. Sorry,  in this case the geometry is flawed.  If you look in top view and front view, one can see the 'loft lines' are waving about.  This is causing stress in the loft, resulting in some sunken bits and some bulges.  Also checking the ACIS Audit report, it gives a high priority ACIS error.

Using just 3 profiles.  If you select loft tool, click the back profile, then the 6th from the back, then the largest of the front triangles. finish loft, and look the loft lines, that's the sort of thing one should aim for, nice smooth lines.  Not necessarily easy too obtain on a boat hull,  but the smoother, the better the loft.   Its made more awkward, as you have varying profiles, some just polylines, some with arcs, and some with hardly any nodes.  But playing around with the node positions may get it a bit better.




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* January 25, 2019, 01:59:41 PM
#6
Cant work out why this profie an has irregular loft from the top to bottom side (black visible) when draft rendered in world plan.

At least one of the profiles is not symmetrical. Attached screenshot shows a profile -- chosen at random -- in Right view, Edit mode. Note the asymmetry of the blue nodes.

Henry H

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* January 25, 2019, 02:57:36 PM
#7
At first looks after Murray posted it seemed to me that his answer was correct, but I dont understand what are artifacts related to tcw?

3 days back I drew the basic profiles in 2D polylines and I got close to a suitable lofted design but after editing 2 or 3 profiles for refining the design things went wrong where I was getting no lofting due to either open and closed 2D polylines or null pointers. After realising that to edit a 2D polyline in 3D I needed to use a 3D polyline and further editing made things worse to the point that Andy picked and Henry picked up on. So I will redraw using a simpler approach with less loft profiles using 2D polylines. This design was originally done in 2017PP and I opened it in 2018PP but Im having display issues with the 2018pp version. An example 2018 problem is where the screen does not display a line drawn until you finish the line length.


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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 25, 2019, 04:21:29 PM
#8
The artefacts that often result in rendering are visual aberrations resulting from optical effects like reflection, refraction, lens flare, and others.  They're illusory, not part of the geometry.  Henry's detective work shows a flaw in your geometry, Daz.  Hulls are usually lofted in halves and mirrored, BTW.  If you're interested in hull building, check out Marcus Bole's PolyCAD program at polycad.co.uk.  It's free, interoperable with TC through IGES and has brilliant curve and surface development tools, and does parametric hulls, compartments and hydrostatics.

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* January 25, 2019, 05:08:25 PM
#9
Murray thanks for the tips. I will post updated geometry if I get it right with less profiles.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 25, 2019, 05:24:25 PM
#10
Murray thanks for the tips. I will post updated geometry if I get it right with less profiles.

I'd suggest using Spline profiles, Daz, taking pains to assure the same number of nodes in each.

Henry H

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* January 25, 2019, 05:41:25 PM
#11
Henry I gotta admit that using 2D polylines, splines, 3D polylines or other drawing objects is not defined clearly. Where I mean the pros and cons for each type when drawing for lofting etc. Its only after members post their respective problems that we do learn more. Ive stayed away from splines upto this point as I was not understanding how to use them, point is 2D polylines are easy to work with but they have led me to the errors that I got to fix now so I will try splines.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 25, 2019, 06:31:53 PM
#12
Henry I gotta admit that using 2D polylines, splines, 3D polylines or other drawing objects is not defined clearly. Where I mean the pros and cons for each type when drawing for lofting etc. Its only after members post their respective problems that we do learn more. Ive stayed away from splines upto this point as I was not understanding how to use them, point is 2D polylines are easy to work with but they have led me to the errors that I got to fix now so I will try splines.

I'll admit that Splines are more difficult to work with. I nearly always have to edit a Spline after drawing it, tweaking its shape.

Henry H

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* January 27, 2019, 09:55:59 PM
#13
Got reasonable results from lofting with 2D polylines, 3D polylines, failed to loft on splines by control points and got a clean result with splines by fit points. The loft with splines by fit points needs more editing to create a flat bottom near the transom but generally Im happy with that. I suppose that the spline loft with control points failed due to different numbers of nodes. Now see what Andy was meaning by stressed lofting when compared to the splines by fit points loft.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 27, 2019, 11:07:21 PM
#14
When using the splines for lofting is there any way to control the thickness of the loft before or after. What Id like is the ability to create a thickness like a solid so that once the main shape of the hull and deck is designed it can be shelled or a smaller copy can be subtracted from the larger so that I can then design elements to go within the hull?

Or is there an alternate drawing tool that I should use in this case?

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 28, 2019, 09:07:52 AM
#15
When using the splines for lofting is there any way to control the thickness of the loft before or after. What Id like is the ability to create a thickness like a solid so that once the main shape of the hull and deck is designed it can be shelled or a smaller copy can be subtracted from the larger so that I can then design elements to go within the hull?

Or is there an alternate drawing tool that I should use in this case?

Shelling oughta work. If it fails, try slicing the loft down the centerline and shelling the halves.

Henry H

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* January 28, 2019, 01:38:59 PM
#16
Extrude to face can be used to solidify hulls, too.  The thickness of shelling is dependent on the tightest curvature on the surface, and that's exacerbated by using polylines for profiles.   

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* January 28, 2019, 03:14:50 PM
#17
Extrude to face can be used to solidify hulls, too.  The thickness of shelling is dependent on the tightest curvature on the surface, and that's exacerbated by using polylines for profiles.   

Murray does the same above apply if you use Splines?
because...

The loft with splines by fit points needs more editing to create a flat bottom near the transom but generally Im happy with that.


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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 28, 2019, 03:32:50 PM
#18
This is just an example of profiles designed by using 2D polylines for a solid hull and while it did result in a solid hull, the shape of the loft was stressed as Andy put it and displayed some artefacts that appeared odd when rendered ( read bulges in the lofted shape ). So I did not move forward with this approach.
see like this.png

I remember reading a post by Darrell about lofting and I think he mentioned that you can control the thickness of a loft, so Ive got no idea on how that can be done but if so then my ideal profile would be 50mm thick from my spline post with pictures above. That way I could then mirror copy and join the halves after lofting and then finally work inside the hull for say like bulkheads and engineering objects etc.

http://forums.turbocad.com/index.php/topic,9176.msg53515.html#msg53515

Can you control the thickness of a loft from splines?
or is Murray approach the only way ahead?


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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 28, 2019, 05:56:01 PM
#19
Getting closer to the goal of a good loft with the splines. So what I might try next is to recreate these splines as 3D polylines and close them up like a 2D polyline and see if I can get a thickness that way. By trying to close them as 3D polylines then that gives me a solid within the hull to place objects onto and not have them exposed or protrude through the hull.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 28, 2019, 06:01:17 PM
#20
Getting closer to the goal of a good loft with the splines. So what I might try next is to recreate these splines as 3D polylines and close them up like a 2D polyline and see if I can get a thickness that way. By trying to close them as 3D polylines then that gives me a solid within the hull to place objects onto and not have them exposed or protrude through the hull.

I doubt that 3D Polylines will help.

Can you post the .tcw in which the profiles are Splines?

Henry H

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* January 28, 2019, 08:36:21 PM
#21
Here ya go Henry

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 28, 2019, 09:28:52 PM
#22
1st attempt to create a loft from 3D polyline with a thickness of 50mm.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 29, 2019, 01:25:52 AM
#23
So heres a 3D polyline loft from multiple profiles. Had to set the local use compound profile to make the loft work. The draft result looks like its stressed and not that great a render.

Kept getting this warning msg "The object cannot be created, Section must be on different planes",. Soon as I set the loft to use the local use compound profile the error message stopped and it lofted. 

Still got some tidying up to do on the starboard aft deck line.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


January 29, 2019, 03:44:33 AM
#24
Hi Daz,

if you are drawing for looks, then TurboCAD can produce a pleasing model, with a lot of work.  However, if you are attempting to draw a real-life hull, then you
may struggle to produce an efficient hull shape, particularly with compound curves, i.e. non-developable.

Is this design specifically for a multihull?  I ask, because the beam to length ratio appears a bit large for a monohull.

If you need an accurate, fair, hull shape for production, which has high hopes of floating on her lines, then I would suggest initially using other programs to derive the hull shape, which can then easily be fitted out using TurboCAD.  For this I would recommend either Rhino 3D or DelftShip, both of which are fully functional (and free), for your needs.

I hope this helps.

Regards Tim

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You can design without engineering, but you cannot engineer without design.
Using Win 10 with Designer 2017 and TurboCAD Pro. Plat. 2016/2017/2018 + Lightworks (64-bit versions) + AnimationLab.


* January 29, 2019, 09:01:20 AM
#25
Rhino 3d offers a 90 day trial.. doing one now with 34 days left..
 Very nice to have along side Turbocad and SketchUp
« Last Edit: January 29, 2019, 09:02:54 AM by dbottesi »

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* January 29, 2019, 02:41:55 PM
#26
This hull design is based on an RAN ship that I spent many years on, I decided to draw this as a learning aid to better understand lofting in general and more specifically splines etc. Attempting to use 3D polylines was just a small exercise to see what if it could be done, to this end its almost viable in that its the solid that I needed which would be sliced along the major bulkheads thereby permitting me to work within the hull and place objects internally. Then rebuild to a model that I could further develop. So Im posting the 3D polyline file so that others may learn and or highlight my errors. Testing the hull design and trying to improve via polycad from the uk. My goal was and still is to create a solid model that has a thickness of say 50mm throughout the hull for ease of use.

Tim thanks so much for your talented insights and thoughts on this design.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 29, 2019, 05:17:34 PM
#27
3D Polylines and 3D Splines are called "3D" only because they do not have to lie in a single plane. They are not necessarily better suited for lofting than 2D Polylines or 2D Splines.  For this boat hull, I can see no advantage whatever in using the "3D" versions of Polylines and/or Splines.

Henry H

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* January 30, 2019, 12:59:46 AM
#28
Henry after your last post I had to find out for myself the reasons behind you saying that 3D Polylines would be no better. So know I understand why, it appears to be the number of nodes or the result of the nodes from a 3D polyline when I traced over a spline. For what its worth splines do give the best results by far when you see the following images. So Im now back to the same question is there a way to give a loft some thickness?



 

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


January 30, 2019, 04:07:15 AM
#29
Hi Daz,

now I see (said the blind man).  :)
RAN ships were built for speed, rather than comfort for the crew! 
Hence the long, slim hulls were fast but generally stomach-churning for the occupants. 
Yes, an interesting project.

I tend to agree with Henry, concerning the use of 3D polylines. 
I would encourage you to concentrate on surfaces, generated from 2-D entities, until you are happy with the fairness of the hull. 
Shelling, to produce a solid, of whatever thickness suits your needs, should then be a straightforward process, IMHO.

Are you in possession of a lines plan or table of offsets?
These may be available from Navy archives?

You have encouraged me to look at PolyCAD again, something I have not done for a few years. 
Murray often advocates its use. 
Your surfaces should translate well, via iges format, back-and-forth to TurboCAD.

Regards Tim
« Last Edit: January 30, 2019, 04:22:30 AM by Tim Stewart »

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You can design without engineering, but you cannot engineer without design.
Using Win 10 with Designer 2017 and TurboCAD Pro. Plat. 2016/2017/2018 + Lightworks (64-bit versions) + AnimationLab.


January 30, 2019, 10:12:35 AM
#30
Hi Dazzy

Had a play with one of your drawings to see if i could get it to loft well.
I tweaked the splines slightly, especially the small one at the front and used Guides (created from snapping to the vertical ones) to help to stop the loft inside faces piercing through the outside when it gets thickened by 50mm..

Hope this helps...

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Daz...
V2018 64-Bit & 32 Bit Platinum Edition
RedSDK Only in 64 bit & 32 bit = RedSDK & Lightworks
TurboCAD user since V3 and Turbocad 3D V1.
OS Windows10 Pro 64bit Lenovo W701 Laptop, 24GB Ram, 2 x 128 SSD harddrives, NVIDIA Quadro FX 2800M Graphics, Intel i7 CPU...


* January 30, 2019, 01:37:15 PM
#31
Just on my mobile phone atm so I will give a proper reply soon. The idea behind this was to teach myself how to use splines and 3D polylines etc to create good curved surfaces. Learned so much more along the way about tc so thanks to Henry, Tim, Darrel for your contributions.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 30, 2019, 02:50:03 PM
#32
Just on my mobile phone atm so I will give a proper reply soon. The idea behind this was to teach myself how to use splines and 3D polylines etc to create good curved surfaces. Learned so much more along the way about tc so thanks to Henry, Tim, Darrel for your contributions.

You're welcome, Darryl -- but IMO 3D Polylines are rarely useful in creating curved surfaces, mainly because it's difficult to incorporate curves into the Polylines themselves. 3D Splines, however are sometimes appropriate.

Henry H

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* January 30, 2019, 02:56:51 PM
#33
Darrel. Thank you, this has made my day. Gotta fess up that Ive been using tcw2017 up till now, why because its been the most stable and reliable, After downloading the 2018 update this version is working just as good, so I will now concentrated the remainder of the design in 2018. Wow 2018 and your work here has demonstrated that these splines have surpassed and surprised me as to the simpleness and elegance of the features here, not to mention the sheet thicken tool. There is no appreciable difference when toggling the ACIS Degenerative Faceting on or off and this is now a game changer for me anyway. AWESOME. That feature on the bow is for the ships anchor chain guide, its somewhat unique in the way its designed but I havent drawn it yet.

Tim. Agree that 3D polylines are unsuitable for generating lofts as they have so many nodes after I traced over a spline in an attempt to create a close copy on the shape of the original spline. So in that regard Henry was right all along. I have no plans other than 1 reasonable pdf image of the ships hull. So a lot of the work is just compromising along the way. I do have 1 very high quality picture ( memento ) that hangs on my wall at home taken from above by a helicopter.   

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 30, 2019, 06:44:17 PM
#34
For those that are learning like me, this picture details the substantial differences in the structure of a Spline v 3D Polyline for lofting. So the spline has about 8 nodes, whereas the 3D polyline has more than 60 ( I gave up counting ) nodes and this is why the original lofting from a 3D Polyline became stressed and the render was poor and it had many facet edges on the side of the hull.
« Last Edit: January 31, 2019, 04:16:06 PM by Darryl W »

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


January 31, 2019, 02:19:48 AM
#35
Darrel. Thank you, this has made my day. Gotta fess up that Ive been using tcw2017 up till now, why because its been the most stable and reliable, After downloading the 2018 update this version is working just as good, so I will now concentrated the remainder of the design in 2018. Wow 2018 and your work here has demonstrated that these splines have surpassed and surprised me as to the simpleness and elegance of the features here, not to mention the sheet thicken tool. There is no appreciable difference when toggling the ACIS Degenerative Faceting on or off and this is now a game changer for me anyway. AWESOME. That feature on the bow is for the ships anchor chain guide, its somewhat unique in the way its designed but I havent drawn it yet.

Tim. Agree that 3D polylines are unsuitable for generating lofts as they have so many nodes after I traced over a spline in an attempt to create a close copy on the shape of the original spline. So in that regard Henry was right all along. I have no plans other than 1 reasonable pdf image of the ships hull. So a lot of the work is just compromising along the way. I do have 1 very high quality picture ( memento ) that hangs on my wall at home taken from above by a helicopter.

Glad to be of help Darryl
A youtube video showing in Rhino it's analytical Curve tool to look for problems in curves is why often we also have problems in TC as our curves are over what the ACIS engine can cope with when further transforms are required.
Making sure we keep node count down to a minimum and check handles using the node editor - The video does help get an insight and something we can all learn from when setting up our curves - http://www.youtube.com/watch?v=OV8SRcYpI2U


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Daz...
V2018 64-Bit & 32 Bit Platinum Edition
RedSDK Only in 64 bit & 32 bit = RedSDK & Lightworks
TurboCAD user since V3 and Turbocad 3D V1.
OS Windows10 Pro 64bit Lenovo W701 Laptop, 24GB Ram, 2 x 128 SSD harddrives, NVIDIA Quadro FX 2800M Graphics, Intel i7 CPU...


* January 31, 2019, 12:04:16 PM
#36
One of the reasons that I evangelise PolyCAD is its smoothness indicators, available for curves and polylines.   The less exaggerated the comb, the smoother the curve, which makes your lofting and shelling more reliable and predictable.  You see the difference between polylines and curves?  If you're lofting with polylines, unequal vertex counts make a mess of lofts, TC is more relaxed about node count differences with curves.

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* January 31, 2019, 04:25:15 PM
#37
Darrel downloading now and thanks for the tip.
Murray great tips, it would be awesome if we had these tools in tcw.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 31, 2019, 07:06:05 PM
#38
Want to bend the acis object to the spline can someone explain why it fails for me?

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* January 31, 2019, 08:02:49 PM
#39
Want to bend the acis object to the spline can someone explain why it fails for me?

There's something wrong with the Spline. Not sure what the problem is exactly, but I traced it with a new 3D Spline by Fit Points and this new path works OK. Modified drawing is attached. You'll want to fiddle with the "Initial angle" in the Selection Info palette.

Henry H

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* January 31, 2019, 08:45:08 PM
#40
Thanks Henry I resolved it my end as I picked the wrong axis.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* February 01, 2019, 08:59:30 AM
#41
Thanks Henry I resolved it my end as I picked the wrong axis.

Now that's interesting, Darryl, because I can't make it work with your Spline no matter how I designate an axis.

Henry H

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* February 01, 2019, 02:21:33 PM
#42
After playing with your drawing some more, I was able to use your Spline as a path after deleting three of the nodes at the forward end.

Henry H

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* February 01, 2019, 02:31:05 PM
#43
Thanks Henry I resolved it my end as I picked the wrong axis.

Now that's interesting, Darryl, because I can't make it work with your Spline no matter how I designate an axis.

Henry H

Neither could I because the spline that I wanted to bend from was a 3D spline ( the help file says by a 2D path etc), so I got this wrong as I had two different splines that modeled the shape of the deck and I picked the 3D one by mistake. The 2D spline was created days ago, when I was just experimenting with the hull splines before further design editing.

I was trying to achieve a bend ( up ) on a flat acis solid with a 3D spline which was always gunna fail ( read the help file! ). I did get it right in the end by using the flat 2D spline and made a copy, moved it up by 50mm in the Z plane and then traced over all lines. Then just extruded it to created a curved deck for the hull which came out ok. see post #40.

see the example bend to path.png
 

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* February 01, 2019, 02:33:06 PM
#44
After playing with your drawing some more, I was able to use your Spline as a path after deleting three of the nodes at the forward end.

Henry H

Is that spline a 2D or 3D?
If thats a 3D spline then what gives cos the help file says a 2D path etc.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* February 01, 2019, 03:17:52 PM
#45
After playing with your drawing some more, I was able to use your Spline as a path after deleting three of the nodes at the forward end.

Henry H

Is that spline a 2D or 3D?
If thats a 3D spline then what gives cos the help file says a 2D path etc.

It's a 3D Spline and the Help file is wrong.

Henry H
« Last Edit: February 01, 2019, 03:41:49 PM by Henry Hubich »

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* February 01, 2019, 06:38:39 PM
#46
After playing with your drawing some more, I was able to use your Spline as a path after deleting three of the nodes at the forward end.

Henry H

Ok, so the help file is wrong. That view from your reply shows a somewhat SE view, so from a front view was the bend to path noticeable. Point being if thats its just a case of deleting some nodes then I want to test for myself.

Was there anything wrong with the spline that you modified?
Why did you just delete 3 nodes?
Why did you delete those 3 nodes near the front?
Or was it just educated assumptions?

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* February 01, 2019, 10:51:29 PM
#47
Getting some great results with bend to path and splines now, this is an image from the port side aft within the steering gear compartment.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* February 02, 2019, 09:03:53 AM
#48


Ok, so the help file is wrong. That view from your reply shows a somewhat SE view, so from a front view was the bend to path noticeable. Point being if thats its just a case of deleting some nodes then I want to test for myself.

Was there anything wrong with the spline that you modified?
Why did you just delete 3 nodes?
Why did you delete those 3 nodes near the front?
Or was it just educated assumptions?

I thought that the nodes in that area might be too closely spaced.

Henry H

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* February 17, 2019, 09:32:27 AM
#49
Here is what I do and it works well. You have to draw a outside outline top(with centerline) and side view of your boat. Then you draw vertical  lines through both top and side view at intervals where your frames will go and how many you want. Now draw lines through you side view usually 2 to 4 at equal intervals or where your curves will  meet approx. Now in the top view you draw inner lines where the straights are and your curves(arcs) at the bow etc. On the right side of these views draw a vertical centerline. Now project your side view lines to the centerline to the right. Then measure in the top view where your frame lines intersect the outside outline from the centerline top view do it for top outline and inner top view  lines. Offset your distance you measured with a parallel line from the centerline to the right now look where it intersects the same top line in the side view. That will be one of your frame points keep doing it for all the lines from the side to measured top view you will get your frame out line pretty accurately. Now only do half a frame and mirror when you have it right it eliminates 50% of errors. I only use curves and lines  and the turn them into polylines as they loft better splines will not. Lay out distances of frames  and draw a line for each also I put each frame on a different layer in case I have to alter it less confusing. Now when your first frame is done take the work plane and move it to the corresponding frame line  then do a " place on work plane" and your half frame will be placed on the  work plane. You will need a centerline here as you have half frames you line the straight center edge to the centerline This will align all your frames. Make sure the height and alignment to the centerline is right before you move on. Try this it sounds like a lot of work but it works and once you achieve this it makes it so much easier and much more accurate. Also use lines and curves and turn into polylines. Now shelling does not work very well for these depending on the shape and contour I found I had to create the lofts in sections to get them to hollow until I got to the area where it would not hollow and in some cases had to create a frame with the wall thickness. Hope this helps.

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* February 17, 2019, 09:03:18 PM
#50
I don't agree with you about deriving the loft from frame stations.   "As built" frames are spaced to attach physical skin to the framework in the most practical manner, using them as profiles to loft often creates surfaces that don't follow intended flows.  It's almost inevitable that more profiles (which don't fit the station spacing anyway) are added to subdivide the loft, more profiles often make the loft less smooth.  Better to loft through as few profiles as actually needed, and to vary the distance between them to modify local curvature or bulge rather than thinking that the loft will obligingly flow as intended through equidistant profiles, an experience like sighting unicorns in my experience.  Hulls and fuselages taper.  THEN derive the rib frame or bulkhead profiles from the hull's profile at their stations.   TC's section and intersection tools, and the drafting palette, give you a lot of ways to derive those contours from a minimal loft more likely to be fair and smooth than a hull that fits equidistant profiles exactly at those stations and evokes Bibendum the Michelin man between them.

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* February 18, 2019, 01:50:30 AM
#51
I also agree with Murray's post but from a practical viewpoint. Like Murray says that using too many profiles can lead to distortion of the loft and thats exactly what Andy H picked up on with one of my earlier posts. Point is Andy noticed that the loft was stressed, which meant that the loft had irregular lines going in many different directions and I had trouble controlling the general loft shape. At the time in that post I had used too many profile splines to try and get a nice loft. After taking Andys advice I achieved a good loft shape when I reduced the total number of profiles.

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


February 18, 2019, 02:48:16 AM
#52
If you have an accurate table of offsets, for a known fair hull, or for that matter an aircraft's fuselage, wing et cetera, then it is reasonable to use these to derive the loft.

However, if you are designing from scratch or simply guessing, then it is easier to use fewer profiles to get fair curves and thus a good loft. 
These curves and surfaces can be checked in suitable software. 
Unfortunately, TurboCAD is lagging a bit behind the competition, in this respect.

Regards Tim

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You can design without engineering, but you cannot engineer without design.
Using Win 10 with Designer 2017 and TurboCAD Pro. Plat. 2016/2017/2018 + Lightworks (64-bit versions) + AnimationLab.


* February 18, 2019, 03:42:35 AM
#53
Tim, I disagree that it's reasonable to use a table of offsets at station points to loft through, especially at the bow and stem of vessels where they taper, for the reasons that I outlined above.  In most use cases, TC won't deliver a satisfactory result by doing that.  It's certainly possible for very sophisticated surface development programs like Rhino, which can define degree 32 spline surfaces, or Maya, or Alias Studio as used by car corporations, or for DelftShip or its predecessor Freeship, but those last two create subdivision surface hulls, not NURB, which don't interact well with associative or Boolean functions in TC or CAD generally.   Most of us aren't using exotics, we're using generic CAD lofting functions like those provided by ACIS, Parasolid or OpenCascade, which will generally extrapolate degree 3 (maybe 4, if I haven't remembered the relationship between degree and order, one is greater by one than the other) spline surfaces through the V direction of a loft, which doesn't give that sort of control between stations.  You could work around to some extent by changing the direction of the loft: if you dig into TC's spline functions, you'll find that you can draw curves of up to degree 9, which have a higher tension, resistance to kinking than curves of lower degree/order.  Taking that into account, you could draw your hull using longitudinal profiles that could be smoother in the bow-to-stern direction.  It might be easier to control a loft in the keel-to-gunwhales direction using longitudinal profiles.  Tables of offsets are somewhat like NACA/NASA airfoil profiles in that they do give you definite points that the surface OUGHT to interpolate, but they don't take any account of the capacity of the tool that you're using to actually do that.  That's why I recommend PolyCAD for hull development: it has functions dedicated to that.         

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February 27, 2019, 09:34:11 AM
#54
I also like playing with boat hull models but I do it slightly differently.  I have attached spline dividers which I add to the model at right angles to the cross sections on the centre line with the flat top part level with the highest point on the cross section that is "highest".  I then shift it up to a level abut twice that of the tallest cross section.

In each turn I move a cross section by exactly the same as I moved the dividers.  I then replot each cross section using the SEKE I where that cross section crosses a divider line.  I use either spline by control points or beziers (my preference) but I do the deck and the hull separately for only from the centreline outwards.  Ultimately when each cross section will be moved back down to original position, the deck and hull beziers are mirrored about the centreline to ensure symmetry.  Note to check after moving each back to its original height that the position along the hull is correct as replotting sometimes mean the new beziers is at PosX but that is simple to copy the PosX or the original cross section into the new bezier to get it in the right place..  When the hull sections are lofted because there is the same node in each section at contiguous positions. the lofts are "smooth".  A fag, yes, but worth it in the end.

I note the bow and stern sections are done separately which is wise as lofting of those can be troublesome.  I see also that the sections are not uniformly spaced and this can add to the uncertainty.  I think also the variations between the cross sections is to severe for good lofting.

As a demonstration of my methods,  I have attached a screenshot of my current work in progress of the Yorkshire coble "Eliza" before mirroring and lots of detail of masts, sails, transom and rudders.

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regards
Colin Reid
TC2018 Pro Platinum 64 bit  + LW plugin on Win10 desktop and  Quad Intel i7 with 32GB RAM + 128GB  SSD and 2TB partitioned hard disk, NVidia 2GB video


* February 27, 2019, 12:59:43 PM
#55
Thank you Colin for your helpful insights ;D

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* February 27, 2019, 08:37:15 PM
#56
Colin I presume that you use your spline dividers in left or right view as an aid to designing the spline profiles. Is that correct?

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.