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#1 Mr. chris baki

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Posted 04 February 2019 - 07:40 PM

Hello to everyone and yeahp i started a month ago laying my hands on CAESES software.

 

So, I ve got some questions that i d like to pose concerning the design of a yacht hull for which i was given an AUTOCAD lines plan (i ve read some related posts but i haven't figured out what is the most suitable way to proceed).

 

To start with when i import the curves they appear on CAESES as NURBS but separated in 100+ separate entries, which are really hard to edi, am i right? 1) So how can i "connect" them in order to further edit them. i guess i can create a polyline -> imageCurve and then traslate it ? 2)if i do that, what is the base point (as we 'd say in AUTOCAD) for the traslation ? is it the starting point of the polycurve? 3)is the aforementioned way the most suitable way (i would like to create a parametric design in order to optimize it)? cause my guess is, that image curve is not really helpful (maybe just to have sth to visually compare) 4}how can i copy/paste let's say these cuvres at another project?

 

Thank you very much for your support,

Cheers to everyone,

 

Chris

 

*At the attached file the imported NURBS curves are under Chine Scope


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#2 Joerg Palluch

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Posted 05 February 2019 - 08:22 AM

Hi Chris,

 

Maybe you can attach an example project so that we better know what you are talking about. Do you have the original file (the one with the NURBS curves that you import)?

 

Currently, there is the issue that if your NURBS curves are linear they will be split up as mentioned by you. This is something we need to check on our side.

 

However, I think in order to create a parametric model for optimization it might be sufficient to import and only visualize the data. Based on this, you can start creating your parametric basic curves (i.e. the most important contour curves) as well as the cross sections that generate the surface. 

 

Can you explain again what you want to do when you said copy/paste?

 

Cheers

Joerg


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#3 Mr. chris baki

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Posted 05 February 2019 - 01:29 PM

Yes, sorry for the missing attached file (had not click attach button).

 

My original imported as .iges files are under scope OR_DATA.

 

Thank you, Chris

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#4 Mr. Heinrich von Zadow

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Posted 05 February 2019 - 03:11 PM

Hi Chris,
 
i took a look at the file and prepared a small demo for you.
 
I would not worry to much about using the imported curves if you are aiming for a fully parametric model. Rather use them to guide your eye when creating a new model from scratch.
Basically, what I would suggest is that you try to recreate the design curves of the hull such as cpc, knuckles and deck and parameterize those curves. Getting from those parametric curves towards a complete hull should be easy. You could simply use ruled surfaces between two curves and add all those surfaces into one Brep. You might even use developable surfaces here having an affordable construction of the hull in mind...
 
I just added a scope named 'exampleApproach' to your file in which I started from scratch. If you click the small icon to the right of the folder you get a nice overview of all the design variables contained and you can play around with the sliders to see how the model adjusts...
 
I hope, this helps to get you started! I would also like to recommend you to go through the provided tutorials to get more familiar with CAESES and parametric modelling.
 
Best regards,
Heinrich

 

fullyParametricYachtHullDemo.jpeg

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#5 Mr. chris baki

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Posted 05 February 2019 - 04:04 PM

Ooow Thanks a lot; i am impressed...

I ll need some time to understand completely the structure prosposed (basically i haven't understood the Generic curve part yer) but really helpful and "inspirational" design approach.

 

Allow me to dig into that a bit and i be full of questions later on.

 

Thank you,

Chris


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#6 Mr. Heinrich von Zadow

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Posted 06 February 2019 - 08:18 AM

Hi Chris,

 

sure, take your time. What I have done with the generic curve is basically two things: I combined two planar curves into one 3D curve and at the same time took care of the parametrization as I want the rulings of my ruled surface later on to represent sections at a constant x-Position.

 

Therefore I 'walk along' the cpc and get the x position for every parameter t. That's what is written in the x(t) field of the generic curve 'in3D'. Again, the reason why I choose cpc to take the x-positions from is that I already have in mid that I am going to use the 3D curve + cpc for my ruled surface so I want them to have the same x position for each parameter t. 

Now for y(t) I do NOT just walk along the parameter t of the curve that defines the y position (named 'zView'), but rather find the intersection of zView at that same x position. Hence it is zView.fv(0,x(t)):y.

For z(t) then follows yView.fv(0,x(t)):z.

 

Of course this is something you can use to play around with. By changing the parametrization of the generic curve (open up the general tab in the object editor after selecting the curve) you can affect the shape of the ruled surface - see the attached screenshots... You can even use a custom parametrization function to allow for maximum flexibility.

 

waterlinesDefaultParametrization.PNG  waterlinesDenseBeginParametrization.PNG  waterlinesDenseEndParametrization.PNG

 

Best regards,

Heinrich

 

 


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#7 Mr. chris baki

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Posted 06 February 2019 - 10:20 AM

Hello Heinrich,

 

Thank you very much for your help. Ok i think i got it, what you did with the generic curve and it is probably the most appropriate solution. I will try to redesign my boat with the suggested approach later today. For now, i would like to continue my current design in order to understand better Caeses and generally CAD. So, if you allow me i d like to pose some more questions and if possible tell me which are my mistakes at my design and way of thinking for the design.

 

First, i d like to ask again what would be the most suitable way to edit the imported Nurbs curves (let's say the deck curve in order to maintain the same curvature and dimensions at deck (Scope:OR_Data->Basic Curves Original) and how to interpolate them at my redesigned boat (New_Sections, New_Chines) ?

Secondly, most importantly, i have trouble creating the surfaces from the curves i ve drawn, so i d like some help creating surfaces at rhe current design.Is it possible to create the desired surfaces or i have to redesign the curves from the beginning? Of course, i admit the your proposed way is much more efficient and i ll try to apply it at the next design and also that i need to gine more details at my bow.

 

Big thanks to all of you in advance, and as you may feel you are the only source of advice within miles.

 

Best regards,

Chris

 

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#8 Mr. chris baki

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Posted 06 February 2019 - 01:26 PM

Sorry once again, i am posting my up-to-now design for my yacht. One thing is that I am having trouble to create the upper part of stem, if i dont follow the path of creating a curve engine and a metasurface i wont have any results?

 

Also, why i cannot generate waterlines up to 2m? I get the warning that sections cannot be generated, even though i cant see where is the mistake...

 

Thank you, once again,

Chris

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#9 Mr. Heinrich von Zadow

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Posted 06 February 2019 - 01:32 PM

Hi Chris,

 

I am not sure I really understand what you mean by editing the imported Nurbs curves. It might be that you are referring to partial parametric modelling techniques such as transformations and free form deformations to allow form variation. In that case image surfaces are what you are looking for, but you can apply those transformations (e.g. Lackenby shift) also further downstream to e.g. a BRep of the complete hull...

About the surfaces you should definitely go through a few tutorials (most importantly meta surfaces) - there is a simple one on a yacht hull that should really help you understand the basic concept.

However, I also created a very simple feature inside your project that allows you to create the main meta surface (from cpc, two knuckle curves and the deck contour). Additionally I used two coons patches for the bow region to close the hull and put everything inside a BRep.

 

mainMetaSurfaceAndCoonsPatches.png

 

parametricYachtHullDesign.png

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#10 Mr. Heinrich von Zadow

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Posted 06 February 2019 - 02:03 PM

Hi Cris,

 

just saw your previous post - of course you can also use ruled or developable surfaces as I proposed earlier instead of the metaSurface - for the bow I would suggest using the coons patch approach I have shown. Note that the coons patches actually take into account the derivatives of adjacent surfaces if they are fed with surface curves (e.g. edges...) - this makes it very easy to achieve a smooth hull!

 

About the waterlines: From what I can see, if you change the draft to say 3m, your waterline moves up as expected on the aft end. However, for the forward end the underlying curve does not reach an elevation of 3 and also the draft is not linked.

 

You should use a polycurve cPoly from c4 and c1 and then cPoly.fv(2,PARAMETERS|Draft) - see the attachment. However, my earlier file is probably already far more advanced so you might want to bring everything together...

 

Cheers,

Heinrich

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#11 Mr. chris baki

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Posted 06 February 2019 - 05:42 PM

Mr.Heinrich,

 

I am really grateful for your help. Allow me to study a bit these designs, run through the tutorials again and come up later on with some questions.

 

Kind regards,

Thank you,

Chris


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#12 Mr. Heinrich von Zadow

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Posted 07 February 2019 - 07:42 AM

Hi Chris,

 

sure, take your time!

 

Cheers,

Heinrich


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#13 Mr. chris baki

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Posted 07 February 2019 - 10:30 AM

Good morning Mr. Heinrich,

 

Thanks again and let me start with my questions concerning file Boat_2.

1)Via feature SimpleTwoKnuckleSection we create a bspline curve that connects points p1,p2,p3,p4 with degree 1. After that via the engine we can create many bsplines from the 4 basic curves (Cpc, ChineLow,ChineUp,Deck), along xPos Curve.

2)After that via MetaSurface we create the desired surface from the Aft_end up to 31.8m (or ChineLow:end).

3)Next, we create the image surfaces just to ensure the continuity between MetaSurface and the 2 surfaces at the bow via that U-Paramter Domain [|SURFACES|main|metaSurface:edge2.ft(2, |misc|WL:start:z), 1] ?

4)Why do we use the imageCurves for the definition of BowSurfaces? to ensure, once again, continuity? If we had used the initial created curves (to define the bow region-under ScopeMisc) we would have problems, right? Also, at the definiton of image Curves we use Source and Domain in order to get the full length of  curves??

5)If i want to use BrepExtrudeEdgesToPlane i need to downlaod it, cause i cannot locate at Breps menu? it is just used to close the surfaces?

6)Finally, how have you designed waterlines, sections, buttocks and they are constantly shown, plus i cannot select them or isolate them? can i deactivate them? They are not offsets? Because

 

These are my questions for now,

Thank you again in advance,

and i know i owe you at least some pines of beer,

 

Cheers,

Chris


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#14 Mr. chris baki

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Posted 07 February 2019 - 10:50 AM

*One more thing.

 

Between Boat2 and Boat3, there are many differences at the waterlines. I mean Boat2's waterlines are much more smoother specially towards the bow region even though the basic curves are the same. Is it due to the way front surfaces are created? The resulted shape may differ that much?


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#15 Mr. Heinrich von Zadow

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Posted 07 February 2019 - 11:28 AM

Good morning Chris,

 

Let me answer your questions: with 1 and 2 you are absolutely right, so 3:

 

It is more a leftover from me playing around. You can probably delete the surfaces and use trimmed image curves for the coons patch instead (see next answer about the image curves ).The tangent information of adjacent surfaces is only taken into account when all 4 sides of the coons patch are surface curves (such as edge, iso-parameter curves, etc... identified by the red curve icon)

 

4. I used image curves because I allows me to easily trim them to the right length (by setting the domain start and end). For the lower bow surface I created an imagecurve c1 of |NEW_SECTIONS|CPC_1. This one I trimmed such that it starts at the same x where the waterline starts (31.8m). Afterwards I created another image and trimmed it at z=0.01 (to make sure it ends just where the radius of the stem starts). I did this in two steps, because the original |NEW_SECTIONS|CPC_1 has two intersections with z=0.01 and by trimming at x=31.8 first I make sure I get the right intersection...

This has nothing to do with continuity, it is just about creating the boundary curves for the coons patches.

 

5. Yes it is just a very convenient way to close the hull by extruding all the open edges to a certain plane. You can use this on any BRep with open edges. Simply create a BRep , then add sources (in our case the 3 seperate surfaces that make up the hull) and then add another operation (click the green plus button 'add new operation' in the object editor with the BRep selected) - choose extrude edges to plane, define a plane, elevation and if you want to close the extrusion and finally TOGGLE the small checkbox next to the newly created operation to activate it.

BRepEditor.png

 

6. For quick section visualization you can use the display options at the very bottom of the object editor of surfaces, Breps etc. Simply activate the different planes to draw waterlines, sections and buttocks and put in a series of the form: start,end:number

You should have this parameterized to make it work even when the hull changes.

SectionVisualization.png

 

Make sure to also play around with the section filters - together with x/y/z view this gives a nice view on the hull in section mode...

 

BrepWithSectionRendering.png BrepWithoutSectionRendering.png sectionsOnlyX.png sectionsOnlyZ.png

 

and 7 (from your newest post): I guess the main difference are the different surface types, but also like I showed to you earlier parametrization of the curves matters a LOT and can be often times used to tweak the shape of the hull.

 

Wish you further good progress!

Cheers,

Heinrich

 


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#16 Mr. chris baki

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Posted 08 February 2019 - 04:49 PM

Hello Mr. Heinrich,

 

How are you? Hope everything goes well.

 

So, I studied a bit and tried a few things around and i am about to start enjoying designing with Caeses. Still, though, i think i need some more help.

I changed a bit the length of the vessel (no prob) and i tried to recreate the bow surfaces using metasurfaces. I wanted to give some more flair at the bow region (which i could not achieve if coon patches were used/or at least was not the desired flair, you can see if you click at existing offset_group "sections"), therefore i used 2 fsplines (as you can read at the scopes (New_Bow_down,New_Bow_Up). But the results are not 100% correct.

 

i cannot achieve to close the surface at the ForEnd, which curves i should use???

Also, there is an ovelap of the surfaces behing 31.8, eventhough both of them should start at 31.8m ??

Finally, there is a problem at the transom area because the section created there goes up to around 2m instead of 4m, can you tell why?

 

If you have time plz guide me a bit more around.

 

Thank you very much for everything,

Chris

 

 

 

 

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#17 Ms. priyanka Gusain

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Posted 10 February 2019 - 05:35 AM

hi all !

 

i was trying to follow modelling of fast monohull but whatever input Im giving nothing is being displayed in the 3D view which earlier was being displayed.

 

How can I see whatever I'm creating in 3D window.


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#18 Mr. Heinrich von Zadow

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Posted 11 February 2019 - 07:41 AM

Hi Chris,

 

I will take a look and try to answer your questions.

@ Mrs. Gusain: Please try to work through a few tutorials first as most basic questions should be answered there pretty well. Take a closer look especially at the new CAESES Help in the Documentation Browser under category Graphical User Interface / Object Visibility.


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#19 Mr. Heinrich von Zadow

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Posted 11 February 2019 - 09:50 AM

Hi Chris,

 

If you really want to use a metasurface in this case, I would recommend you to create the sections for the curve engine at constant z so that they rather represent waterlines than actual sections. This way you can easily extract the tangent from the adjacent surface, set an entry angle at the bow and match your given waterline and deck shape. You will probably get nice results with an FSpline or alternatively a BSpline/NURBS curve based on 4 control points.

 

However, if you just want to have a bit more control over the flare in the bow region, why don't you just parameterize the waterline and deck curves? This should give you plenty of control... If you go back to my first post you will find a good starting point for parameterizing the curves - I recommend you combine those projects into one to have a robust parametrization of the design curves along with the meta surface for the main hull portion and the coons patches (or alternatively another metasurface) for the bow.

 

BTW: You seem to use the FSpline as a straight line in many places throughout the project - you might want to check out the corresponding tutorial as it is a far more powerful curve than that and especially valuable in hull design!

 

Regarding the section at the transom: The hull surface simply does not reach all the way back to -1.7. If you create your first section a -1.6999 the section is cut correctly...

 

One more question: what are all those sections in 'NEW_SECTIONS' for and why do you create them manually?

 

 

Best regards,

Heinrich


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#20 Mr. chris baki

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Posted 11 February 2019 - 11:31 AM

Good morning Mr.Heinrich,

 

Thank you for your tips, and i ll start now trying to design them. So, some questions cause i really have not understood some things.

 

Up to now i have 2(A&B) versions of bow surface but none of them is satisying, therefore i am trying to design versions 1&2.

 

A) SURFACES->BowLow&BowUp : The sections (under Nomeis&Isaloi scope) have an angle at the bow region at wareline's Z.

B) I created a metasurface up to 40.4m (SURFACES->NewBowUP - which btw has an overlap behind 31.8m for which i dont understand the reason) and then i closed the bow surface with a fillet surface(SURFACES->BowWithFillet): In that case sections seem ok and they have the desired flare but the waterlines have a breaking point towards the bow region which i dont like.

 

1) I am trying to create the bow surface as the exemple in fast_monohull but i am having a hard time. My secondFwdSurface is my SURFACES->NewBowUP but after that i get confused on how to create the correct lines(stem angle,xPos etc) in order to design my stem surface. Could you give me some help on that ?

2) I m trying to applicate another way that i read about at the Supply_Vessel_Exemple uploaded at the forum. In this case i m trying to follow the exemple for its StemRadius feature but again the results are discouraging. Could u advice me on that as well please ?

 

*i drew the sections under NewSectionScope just for my help in order to undestand visually the differences resulted from some parameters i tried to change. They are not actually used for the design.

 

Thank you very much.

 

Best regards,

Chris

 

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