Where to start : too much Info?

Next
 From:  ftgil2
3814.1 
Hi
Just purchased MOI v2 this week and I'm really impressed with it so far. However ... I have to model a ships hull and I am struggling to get started.
I have looked at the Rhino rapid modelling demo and they use about 10 curves lofted. I downloaded the demo 3dm file and it worked super in moi.
For my project I have assembled the "outline gridwork" of my vessel in autocad mechanical then exported as iges format then imported to moi. (worked pretty good)
The definition of the shape looks great in wireframe but I would appreciate some suggestions about how best to use this info in moi to create a "sleek" hull surface.
If anything I have so much info that I don't know where to begin.

Thanks in advance for any suggestions for a moi newbie. 3dm file attached

  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  coi (MARCO)
3814.2 In reply to 3814.1 

EDITED: 15 Oct 2010 by MARCO

  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  ftgil2
3814.3 In reply to 3814.2 
Marco,

Thanks for pointers - some nice info.
JPBWEB seems to be the maestro of ship hulls.
However nothing I can see about my particular vessel with a bulbous bow.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  JPBWEB
3814.4 
Hello ftgil2,

Thanks for the kind words. I am still struggling with ship hulls as they can be beasts to shape correctly.

Your model looks a lot like the one in the Rapid Hull Modelling tutorial, that does work very well in MoI as it does in Rhino3D. I have never been able to replicate that approach with any other 'real life' shape though. But for your purpose, you might want to follow the approach prescribed in the tutorial.

I still stick to the advice I gave in one of the threads that Marco indicated. For a hull shape with a very pronounced bulbous bow (or a modern sonar on a warship), I'd consider building it separately as a solid and blending it into the hull using the excellent toolset that MoI features.

One thing is certain: in ship hull modelling, less means more, in the sense that you really need to use the absolute minimum number of curves.

I hope this helps. I am away from my trusty Mac at the moment and thus unable to give your hull a try.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  ftgil2
3814.5 In reply to 3814.4 
JPBWEB thanks for taking the time to reply.
I guess I will need to start with something more basic and try again using using the lofting method and then the network method.
If anyone has any ship hull example files (especially using the network method) I would really appreciate that. - I have got the rhino "loft" one already.

thanks
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Kurt (KURTF)
3814.6 
Are these threads (for ship hull techniques) posted in the Wiki?

Good information there.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Michael Gibson
3814.7 In reply to 3814.6 
Hi Kurt,

> Are these threads (for ship hull techniques) posted in the Wiki?

I've added a link to this thread in to the wiki now, it's on http://moi3d.com/wiki/Resources , under the Tutorials section: "Discussions on ship hull techniques".

- Michael
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Michael Gibson
3814.8 In reply to 3814.1 
Hi ftgil2, just a few general tips and some additional explanation -

Like JPBWEB mentions above, it can be helpful to use as small a number of sections as possible.

That's because each section you add kind of adds some more "pressure" in a certain sense to force the surface to run exactly through it. Additional pressure like that will tend to cause undulations to happen.

You can see an example of undulations just in curve drawing as well, for example if you have 4 points like this and put a curve through them:





You can see the kind of bulging that happens there - that's similar to the undulations that can happen in surface construction as well. It is technically possible to avoid bulging with many sections if each section is very exactly positioned at a kind of incremental smooth step from each other, but in practice this becomes difficult to do with drawn curves because it's hard to visualize exactly how each sub-section of each curve is connected to each other.

One way to avoid bulging with curve drawing is instead of forcing the curve through those points, just make it guided by those points by using Draw curve > Freeform > Control points, which makes a result like this:




The equivalent for lofting is to use the "Loft Style: Loose" option for the Loft command, which does a similar kind of thing for surfaces, the surface is generally guided by the curves but not forced to go exactly through them other than the first and last one. It reduces undulations at a cost of control over exactly where the surface goes through.


So then the other tip that JPBWEB gives above about building a bulbous section as a separate piece is also very good advice. It kind of fits in with what I was trying to describe above with undulations - if you try to model a sudden change in the shape of a surface all within one single loft or network command, it will then be a source of undulations. So try to only make a single loft or single network that has a kind of smooth continuing form to it.

If things change shape in one area, try to create that as an independent separate surface instead of trying to do it all in one go. Then you can use some other tools like Fillets or Blend to make a connection between those pieces.

- Michael

  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  ftgil2
3814.9 In reply to 3814.8 
Thanks everyone for all this good info.
Any example hull scenes for me to dissect?
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
 From:  BurrMan
3814.10 In reply to 3814.9 
""""""""""""Thanks everyone for all this good info. Any example hull scenes for me to dissect?"""""""""""

This thread has some curves from a model to look at...


http://moi3d.com/forum/index.php?webtag=MOI&msg=3002.1
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged
 

Reply to All Reply to All