Hi all,

heres an image that I tried modeling in MOI but couldnt, so I ended up modeling it in Max. But subs are allways a little hit and miss compaired to the cleaness of nurbs

So...does any one know how to model this in nurbs, I be greatfull for any tips and hints

Cheers!

Actually that one looks like a good candidate for NURBS modeling.

The main idea is that you've got to think more in terms of larger sheets.

The tricky part is that those larger sheets are often going to be extended further than the final model result because you're going to trim them with other things to produce more details such as cutouts or indentations, etc...

This idea that you're going to discard portions of your shape later on in the modeling process is a really different thing than what you do with polys/sub-d, so it can take some getting used to.


You don't want to follow all the final details of your end result shape while building the initial sheets - the initial sheets should be broader and more simplified and kind of provide the basic underlying form. You get more of the final detail as you intersect and trim out various bits after some underlying pieces are in place.


Here are some steps (here I am replaying by undo/redo steps) to show the kind of general idea:



I started by drawing some curves, then did a sweep for the central body sheet. Then the side looked rather mechanical with a totally flat piece so I did another slightly curved sweep to make a side sheet. Then I moved those sheets so they were punching through each other and use Fillet to trim them and build a smooth connection piece.

There are still several other steps needed to finish the model, but I hope this might give you a good starting point for how to start to approach forms like this with NURBS.

Since it is not a very mechanical shape, you're going to end up using surfacing tools like Sweep and Network primarily and not so much extrusions unless your shape is fairly blocky.



- Michael

Hi Michael,

thanks very much for the time you have taken in putting this together for me!

I will try this and let you know how it goes

cheers

And another little demo here to plant some other ideas - here I produce a much different shape along the side, while keeping the central zone the same as before, by editing the path curve for the side sweep:



That's something that can be good with NURBS modeling - you can set things up so that you can produce some pretty broad variations just by editing one or two profile curves instead of trying to manipulate every single point of the final result.

- Michael

one other quick question

Is there a way to view the model as shaded only, ie...no wireframe/goasted parts, just smooth object?

And thanks again for the update!

You're welcome!

It is a much different mindset so I would not be surprised if it takes a bit to get used to it.

If you get stuck on something, please post your .3dm model file of your current results here so I can see where you may be getting held up on and try to give some suggestions.


This is kind of getting into a somewhat more advanced area of more surface modeling techniques, it can take some more time to develop the skill set for working on this kind of stuff as opposed to solid models where the shapes are well defined by only using extrusions and booleans.

- Michael

> Is there a way to view the model as shaded only, ie...no
> wireframe/goasted parts, just smooth object?

If you're using the v2 beta, go under the View tab on the side pane and uncheck "Display hidden edges" to turn off the dashed hidden line display.

Then if you want to temporarily get rid of the non-hidden edge display as well, you can do that with a keyboard shortcut. There are 2 different ways you can do it, you can use the script on Petr's page here:
http://kyticka.webzdarma.cz/3d/moi/#ShadedDisplayMode

which will hide all edges (it's the same as selecting them manually and using Edit/Hide to hide them), or another way which I actually use is to set up a keyboard shortcut to save to a polygon file format, and on the meshing dialog there you can choose the option for Display: Shaded there.

To do that, set up a shortcut key with this command:
SaveAs c:\test.obj


That can be a handy shortcut for checking what the meshing looks like at various times when you are modeling as well. Just hit escape or push the cancel button to bail out instead of actually writing the "test.obj" file out.


At some point I'm going to have more display options listed under that View tab.


- Michael

Just aquick, rough, play.
Not done the side bulge yet--but should be simple.
(I see better/accurate ways are explained by others.)

Brian

And heres a bit more fiddling

And, now, it's grown into a Train!
(I am having fun!)
Brian

and even MORE!

Cheers all for your help!

Iv got another question. today Im just experamenting with the software, trying to remember how I used to do this stuff with patch modeling in maya.

Anyway.. what I now want to try is getting this working.

I have made the side section, bolean out the shape and now I want ot patch the face of it. But...no matter how I try this Im not able to make it a smooth object, even though the curves are all snapped correctly (to tangent etc) and Im using the "tangent" option within "sweep" I just cant get it working :(

If any knows something I dont please let me know!

Hi...

Try this :

Hi Anis

cheers for that, but I actualy want to keep the shape inside/on the 3 curves (going down the middle) Iv drawn. So the tightness of the shape changes from top to bottom.

How about this...
Create using Network, offset curve, project curve, trim, blend then mirror.

ahhhh....thats an intresting way of doing it. Ill try it!

Cheers again!

Post your end result, good luck ;)

heres an update, thanks all for your help. In the end I did something similar to what Anis surgested...

Between red and blue I blended the shape together.






I am a little disaponted that getting the basic shape took me so long, all of my problems were getting the curve between red and blue the way it was on the real train. It would have been great if there was some controls to handle the amount of tangancy/buldge at the start and end of the blend shape. I found that because the amout of blend was tight at the top and more loose at the bottom that getting it working correctly was a real pain

Hi mushroomgod - the "tangent" mode for sweep is for a special setup where you have all cross-sections being planar slices all arranged to be on parallel planes, some details on that here:
http://moi3d.com/1.0/docs/moi_command_reference7.htm#sweep
It doesn't look like your profile curves are all on parallel planes, so that option won't do anything for your case.

Right now MoI only has some limited tools to ensure smoothness - you generally need to use the Fillet or Blend tool for that, commands such as Sweep or Network do not right now have the functions inside of them to adapt the surface to maintain smoothness to an already existing one.

So generally the method is that you don't actually try to make them smooth yourself directly when your surfaces are first created - make them intentionally creased and then put a fillet in between them to make a smooth connection automatically. If you check out those steps I was using previously in this thread here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2164.2 that i the method that I was using there.

In the example that you show, you're basically trying to do the fillet's job all built into the sweep at one time - that is not going to work in MoI currently.

In the future I do want to add some more options into sweep and network to ensure smoothness with adjacent surfaces, but those are some fairly advanced surfacing techniques, it will be a while before those are added into MoI.

- Michael

Hi mushroomgod - here is an example with the file you posted:

Using your same side surfaces, but build a sweep that is a flat piece instead of trying to make it rounded at the corners:



Then use Fillet to produce the final rounded areas:




You may want to use the Shape: G2 Blend option in fillet to put a more flexible blend in there instead of a circular arc.

- Michael

Hi Michael,

Yeah I figured as much, no problem though, the shape I have now is pretty much spot on, I think the client will be happy :)


I think MOI does boolians and fillets so well the only thing its really lacking (for my style of modeling atleast) is like you say some good tools to maintain smoothness over a number of different patches/networks.

But for everything else the software is worth its weight in gold!

for example, this (cant remember if I posted this)..very simple and super quick - 90% moi

Beautiful work, both geom and render.
David