Full Version: Ship hull tutorials

Show messages:  1-3  …  44-63  64-83  84-103  104-123  124-129

Hi Gord, so I was thinking of how to explain this... One of the reasons why you're having problems with the ship hull is that you're sticking too much to the "solids and booleans" type modeling method when working on the hull.

When you're working on something like that it's better to work for a while in something like a "skinning" type mode where you want to focus on getting surfaces that touch each other accurately at their end edges. The way to ensure that is to either have 2 adjacent surfaces either constructed from common curves or have them extend through each other and cut each other with the Trim command, then the intersection will be accurate enough to join.

When you're in "skinning mode" you don't want to use booleans. Booleans are good when you're working with solids. But one of the things about booleans is that they are expecting objects to cut each other and for some material to be removed. If the pieces have freeform surfaces that come close to meeting but don't quite align precisely enough then you can end up with little slivery pieces being generated from the intersection. That's what I was trying to show in this previous message: http://moi3d.com/forum/index.php?webtag=MOI&msg=9819.90

So to avoid that when you're in "skinning mode" you don't want to use booleans, you instead use Edit > Join to glue surfaces together. Unlike the booleans the Join command does not try to do any surface/surface intersections and does not try to remove any material, it's only job is to glue edges together to make a larger skin. When you have formed all the pieces and glued all edges up then you'll have a solid and you can then switch back to boolean operations then.

Basically you want to be using a different area of the toolset when you're working on the hull, using the surface modeling tools Trim, Join and Blend and not booleans right then. It's a more advanced aspect of NURBS modeling and has a longer learning curve. Also models that are going to need a lot of this type of work can potentially be easier to do with subdivision surfaces rather than with NURBS.

- Michael

---

Wow! What can possibly go wrong there when I try it as a texture!

Thinking on though, I think just plate lines 'scribed' into the surface would be better to avoid an overscale look. Is this possible. Do I use curve to project them on? I realise I'd need to make solid lines and use boolean to cut them into the surface somehow?

G

---

Thanks. It's because I come from a modelmaking background so will be trying to do things as I would in the real world! I'll give that a go.

---

Hi Gord, yes it's possible to cut grooves, check out here for some previous discussion:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3859.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=4162.8
http://moi3d.com/forum/index.php?webtag=MOI&msg=1654.2

- Michael

---

Hi Gord,

re:
> Thanks. It's because I come from a modelmaking background so will be trying to do things
> as I would in the real world! I'll give that a go.

Yes solids and booleans for mechanical parts matches up pretty well with real world manufacturing with stuff like a cutting tool removing material from stock.

The "skinning mode" type approach doesn't match up so well to real world processes, that's part of why it has a longer learning curve.

- Michael

---

Normally for building classical hull just sections and "Loft" them must do the job!
and for drawing them just half sections! :)

I believe even the name of pro builder boat's hull in real world is named "Lofter"...

Am i right ? ;)

---

OK, pretty pleased how I got it so far with all your help! Now I try adding strakes to the outside of the hull using sweep and profiles with a rail progected onto the hull. It looks like it worked well. Except when I try to join, it won't have anything, but when I try to boolean it on, it simply disappears leaving the profiles and rails.

Image Attachments:
Screenshot 2020-06-11 at 23.15.13.png 

---

Hi Gord, re:

> Except when I try to join, it won't have anything, but when I try to boolean it on,
> it simply disappears leaving the profiles and rails

So to use Join you can't join something in the middle of another surface, you can only use Join to glue an unattached edge to another unattached edge. So you would need to cut a hole in the hull surface in order to get it set up for Join.

The sweep actually didn't go too well, it's not a solid, it's got a kind of twist in it:


Also that's not a good setup for doing a boolean, back in this previous post (http://moi3d.com/forum/index.php?webtag=MOI&msg=9819.102) I wrote:

   "Yup, that should be possible. But one thing to watch out for is when you make the sweep make the sweep push halfway through or at least a little ways through the hull. Don't make something that has a flat edge that just barely skims right along the same surface area of the hull because such things can be difficult to intersect with booleans."

Your case here is a good example of what I was trying to describe not to do - to set up something that will boolean well, don't make your sweep have a flat edge that is going to make a surface that skims along the hull surface:


That's inside flat piece is close to the hull surface, but it is not going to be exactly the same shape as the hull. It's going to kind of dip in and out of the hull by small amounts and that makes for a really complicated intersection between those surfaces. You need to make the sweep sink in a ways past the hull surface, not have a piece of it that skims right along its surface area.

I think the twist problem with your sweep probably comes from having 2 sweep profiles that have a different number of segments in them. Can you post the curves you used for the sweep so I can check those out?

- Michael

Image Attachments:
gord_sweep.jpg  gord_sweep2.jpg 

---

1 draw lines straight ... polyline with large fillet ... curves etc ... rebuild them

project on the surface and trim ( boat + lines ) and copy paste the 3 lines

2 draw profile for the sweep ... scale it

3 rotate and adjust carefully the position of the profile ( not inside the hull ;)

save before sweep

sweep one on one

4 the third line is not trimmed it turn around the hull so the swwep produce a crap

cut the third line ... mirror it along the boat axe

when you have 2 sweep ... build a round piece with loft and boolean union

each sweeped piece is solid and can be boolean diff with cut line ( the end of the second sweep is bad ... need a cut with an arc placed on top view for example )

I can't replace the third piece on the hull ( scaling manipulation error ... doomdoom )

file joined

( il faut vraiment que j'achete un dico anglais ;) comment avoir plus de 200 mots de vocable dans le parlé de Shak'spire ;)

---

ensuite ... les chaines ... l'ancre ... et un vieux filet qui pendouille ... ;)

---

excellent script chainmaker by bemfarmer

http://moi3d.com/forum/messages.php?webtag=MOI&msg=6087.61

rigid or torsion .. size .. angle.. all is customizable

when done ... the chain has separate parts easy to group and move rotate duplicate etc ...

edit point allow to change the shape of each curve ... copy paste for more complex group of chains

and if you want more personnalized chain ... create a shape ... Array along curve does the job

---

@ Corchet Capitaine Hadock ;)
Pas besoin d'acheter des dicos!
Pour le tout venant d'un site en langage châtié : https://www.deepl.com/translator
Le plus complet comme dico : https://www.wordreference.com/fr/

Belles châines déchaînées!

---

Looks interesting!

---

That totally works! Thanks!

---

This thread reminds me of all the problems I had creating Fuselages for Aircraft with nurbs.

Gord
If you haven't already explored this option its worth trying using the loft, loose, exact method. See Andrei's video about 10 minutes in https://youtu.be/WBVUsr-eYdw
The trick with this technique is that all your hull cross section shapes must have the same number of points on them.

After you've lofted the hull shape, you can go back and tweak the points of you splines to create a nice smooth surface that matches your reference images & photos (as closely as possible).
Lofting also allows sharp changing of direction with nurbs without the artifacts and distortion that often occurs when using networks and sweeps.

---

Thanks!

Sometimes though, swept rails just won't boolean into another solid surface, whereas others had no problem. See the two rails on his one. And why, when you boolean does the object sometimes disappear?

---

the "Lofter" as i said in my previous post! ;)
https://moi3d.com/forum/index.php?webtag=MOI&msg=9819.109

---

Don't hesitate to "inflate" your object before the Booleans operations!

---

Hi Gord,

> Sometimes though, swept rails just won't boolean into another solid surface, whereas others had
> no problem. See the two rails on his one.

Similar to how it is difficult to intersect a surface that skims right along another surface area it can also be difficult to have skimming edges like you've got here:



Another problem is in this area where you're trying to boolean there are some microstructures:




It will probably be difficult to do a boolean cut that has to try and intersect through that messy area.


> And why, when you boolean does the object sometimes disappear?

Part of the sequence of doing a boolean is it intersects the 2 objects and then needs to gather well formed closed intersection curve results which it then uses to partition objects into different pieces. If it was not able to get a good closed intersection then it can get confused about how to divide pieces up. The pieces that disappear were being classified as being in the volume that is to be discarded. If there are a lot of little tiny fragments in the area that is being intersected they can get partially glommed together and that can impede getting a well formed close intersection.

So it's not good to do repeated booleans of pieces that are kind of close to being aligned but just a little bit off, that can make those little slivery pieces.

- Michael

Image Attachments:
gord_microstructures1.jpg  gord_microstructures2.jpg  gord_sweep_edge.jpg 

---

That's basically a problem area to work with since these original hull surfaces didn't align very precisely here like I was talking about earlier above:



This area at the top of that juncture now has problems with edges not meeting up with each other very closely and that kind of loose tolerances will tend to increase "glomming together" in intersections through those spots.



If you're going to be doing more stuff along those joining areas then it's good to get them aligned cleanly from earlier on, it helps to avoid problems further down the road.

- Michael

Image Attachments:
gord_surfaces_not_aligned1.jpg  gord_surfaces_not_aligned2.jpg 

---

Show messages:  1-3  …  44-63  64-83  84-103  104-123  124-129