Hi Kevin,

> Everytime I use the scaling rail I get a little tear in my
> nurbs surface just near the end. Is this a display error or
> likely to cause meshing problems later on ? (see attached image).

That looks like the kind of dropoff that can happen if the scaling rail did not traverse the entire length of the sweep, it basically can abruptly stop influencing the scale at that spot.

Here's an example with a one-rail sweep. Here is a one rail sweep with the scaling rail off to the side:




When the scaling rail is applied, the profiles will scale out away from their normal plane until they hit that scaling rail:




If the profile is not able to find any intersection with the scaling rail, it will just stay its normal size, which may cause an abrupt change in shaping.

Since the scaling rail is applied in this manner, it is not a bad idea to extend it a ways past the start and end of the sweep so that you know the entire zone of the sweep is totally covered with it.

If that is not what the problem was, I will probably need to look at the .3dm model file to see what is happening.

- Michael

Ok thanks, I'll double check that there is not some miniscule distance between my scaling rail and curves which is causing the problem. I've had it happen quite a bit while modelling so I need to spend more time checking those osnaps snapped to where I wanted them to.

Just an observation.
Much of this seems to have been covered in a forum thread back in January.

Has anyone been making reference to that thread?

Brian
(One of the images I posted on that thread)

Michael

Even after breaking my model down into sub components I'm still getting warping, twisting and deformation of my surfaces. To break my model down into even smaller components (to keep nurbs happy) makes it extremely difficult for the user to get all his curves right so that the shape of this aircraft is captured especially once the surfaces are trimmed there is no mechanism to adjust or tweak them. Also the more sub pieces that are created the more shading errors I get when it is converted to a mesh in 3DS Max. By shading errors I mean the joints between the surfaces are visible depending on the light direction.

Thankyou for taking the time to write such a detailed analysis of nurbs v poly and whether this project is right for nurbs. You've confirmed what I suspected, it is not.
I was really hoping that it was so that I could save time and model more accurately with nurbs. As you can see, I am already a skilled polymodeller http://www.websitetoolbox.com/mb/felixdk?forum=107238 and was hoping nurbs would be less time consuming.

At this point I head back to polymodelling unless some ground breaking piece of software eventuates in the future that makes it easier and quicker. Some might say dream on !

I should however still be able to use my investment in MoI to do some of the detailing of the aircraft. For example on the F9F it has a speed break underneath with about 100 holes in it which is almost impossible to do with polys so nurbs will do that easily. MoI will also come in handy for doing cockpit, landing gear details where it is far quicker to boolean stuff.

Thanks for the post Brian. I have seen that model and thread before. It is a very simplified model of mk22 spitfire and only vaguely resembles the real thing. It is relatively easy for me to create a similar model.

There is however a huge difference between making it look like the real thing and vaguely resemble it. Making it look like the real thing is doing stuff that nurbs doesn't like to do unfortunetly.

Hope there is something in this thread for other users on their own projects.

.

kevjon

Sorry, but I think you are missing something about Nurbs.

.You might like to have a look at this.

http://gallery.rhino3d.com/Default.asp?language=&g=7

(Michael was involved with the creation of very recent Rhino app versions you may find. MoI is his "Encore")

Brian

The underlying thing in this thread has been the need to use NURBS properly to get the result.
Trying to model polymodel style with NURBS just wont work. There has to be A change in technique and approach. If a polymodeler wants to use NURBS they have to LEARN!

It's not a NURBS problem. The REAL airplane would be modeled in NURBS by a skilled NURBS modeler and would take a sufficient amount of time. You cant just start "throwing curves around" and wonder why it doesnt work, then make statements about the problem with NURBS. It's not fair to the others who view this forum or are experienced enough to actually model an airplane with a NURBS modeler.

With some time invested one could become skilled enough to model an "AIRPLANE", but lets be realistic.

In a sense,

If you want technical data files with an ability for a machine to MAKE something accurately, you use Nerbs/Cad stuff.

If you want to make an "Image" of something, for some, poly modelling may be better/easier.
It's all in the mind set.
For me, coming from the likes of Hexagon poly modelling to MoI was like the world had become a modelling joy!
But I come (Very originally) from a background of engineering/ fitting and turning and mechanical drawing

Horses for courses.

Brian

PS I can/ have taken my MoI files into the likes of ViaCAD to produce viable dimensioned drawings "blueprints" which model makers could actually use.

Hi Kevin,

> Also the more sub pieces that are created the more shading
> errors I get when it is converted to a mesh in 3DS Max. By
> shading errors I mean the joints between the surfaces are
> visible depending on the light direction.

Yeah, this is related to getting creases between pieces that are built separately from one another, that's described in some more detail here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.18

Typically 2 surfaces that are just constructed adjacent to one another will not be guaranteed to have a completely smooth shape to each other. In the future I do expect to add some more tools to edit surfaces to achieve smoothness to existing ones, but that kind of "smoothness in all directions" is really the great function that subdivision surface modeling provides much more easily and automatically. I mean that is like the primary function of subd.

Currently in MoI to make pieces smooth to one another you would generally use a fillet or blend to build a small smooth connector piece, but that does not work so easily when you want more of a totally smooth skin like thing which is more of what you have in this situation - like more where the different components are very blurred and not really very distinct as different pieces.

That kind of heavy "blurring" between everything tends to be a indicator to lean towards subd for that task.


> and was hoping nurbs would be less time consuming.

It definitely can be if you use it with the models that are most suited for it, that will be stuff that has a more mechanical design to it rather than a kind of "smooth skin" design to it.

I think you've got the right idea - things like instrumentation, cockpit interior, landing gear, parts that have a lot of holes drilled in them, those are the projects where it will become a slam dunk to use NURBS instead of polys. Those are the kinds of projects where the focus on booleans makes things come together more quickly and the "smooth blended skin" main function of subd does not really help...


> At this point I head back to polymodelling unless some
> ground breaking piece of software eventuates in the future
> that makes it easier and quicker. Some might say dream on !

Eventually you will see more of a combination of SubD tools being combined with NURBS surfaces together - that will be where you will have making a subd cage be just another option in creating a base NURBS surface which can then be trimmed or whatever same as the result of a sweep. You can see this in action currently with the TSplines plugin for Rhino. That will be coming into play more frequently in the future but it will take a while before that will get into MoI, MoI is still primarily focused on the type of "boolean oriented" models right now and probably will be still for a fair while yet.


In addition to using MoI for boolean-oriented pieces, one other workflow that may appeal to you is to use some of the surfacing tools in MoI to create a kind of rough base form quickly, then take that into your polygon package and use some of the newish style retopologizing tools to rework it into a sub-d friendly form and then continue to work on it as polygons. That can give you kind of a jump start because you can get a kind of basic rough outline of your shape pretty quickly with the NURBS tools by drawing something like 5 or 6 2D curves.

That helps to leverage one of the strengths of NURBS which is that you can kind of whip out some concept forms quickly by drawing just a few curves.

That kind of combo could be worth looking at I think.


Anyway, sorry that the NURBS toolset did not deliver on what you expected. I think it will be a lot more in line with your expectations for the more mechanical type pieces.

- Michael

Hi Brian

>You might like to have a look at this
Yep I've seen those before. None of them are accurate compared to the real thing and I can see where the user has simplified things in those models to suit what nurbs can and can't do.

>Michael was involved with the creation of very recent Rhino app versions you may find. MoI is his "Encore
Yep, I'm aware of that. I apologise if I have offended Michael or MoI users. Michael is the one who has suggested to me a couple of times that I would be better modelling this aircraft with polys than nurbs. I persisted in the hope that I could get there with Nurbs and perhaps speed up my workflow.

Hi Burrman

I totally agree with you that in order to become a skilled nurbs modeller you have to put the time and effort into it.

>The REAL airplane would be modeled in NURBS
This aircraft is from the late 40's early 50's. No nurbs then, just slide rules and very clever engineers.
Modern aircraft are indeed modelled with nurbs, but not with Rhino or MoI. The toolset of those modelling packages is much more comprehensive and have a huge price tag to go with it. A price tag that is way, way, way beyond the hobbyist, let alone the learning curve needed to learn such complicated software.

>You cant just start "throwing curves around" and wonder why it doesnt work.
I did my best but unfortunately I just wasn't getting the results I wanted which is good clean smooth mesh ready for uvmapping. Just couldn't get those surfaces to go where I wanted and couldn't tweak them to shape either. All the files and blueprints are there for someone to show me how it should be done. I'm still keen to see if it can be done and learn from it.

PS I've edited my previous post of this thread as I have no wish to upset anybody. Nurbs modelling of aircraft is however not for me but that is not to say it is not the perfect solution for someone else.

Hi Kevin,

> Even after breaking my model down into sub components
> I'm still getting warping, twisting and deformation of my
> surfaces.

Just another note looking more closely at your image there - I don't think this will really change any of the key points, but that is not really still the correct "componentization" strategy for what would be required to do this well in NURBS.

You've still got a very polygon-oriented mindset there where you want each component to end up having an "edge to edge" match with an existing piece.

That's not how you want to approach the components with NURBS, instead each component is going to be more of an extended piece that punches through the others, then you trim and fillet or blend them together to make your final connections.


So you've got this where you have stuff laid out constructed edge-to-edge:



NURBS componentization would instead be more like this (just very quick rough sketches for the pieces here):

Fuselage piece:



Canopy piece:



Tail fin piece:



All components:




Notice how each component is a fully independent individual extended piece and is not hanging directly off the edges of another piece.

Then those get booleaned or trimmed, which then creates a sharp edge curve between the components, and then you use either fillet to smooth the sharp edge, or you trim back a bit of a gap and use Blend.

That's more of the kind of componentization that I was trying to get at, sorry I did not make it clearer. Notice how the pieces are constructed separately and there is not a huge effort spent on building them to the exact same final edge - instead those edges are created when you intersect the pieces.

You seem to be avoiding intersection in your approach - the big difference with NURBS is that you want to use intersections into the approach.

Anyway, just some more information... But you seem to really want to control the edges directly - to build the surface directly by controlling all "skin" more directly instead of using intersections, that is certainly more suited to subd instead.

- Michael

Michael

Thanyou for your continued honest repsonses in this thread and taking the time to respond and offer suggestions on how I might overcome problems. All of them have been very helpful and I know it does indeed take time to type responses.

Yes there are definitely some things sub'd is better at and somethings nurbs are better at so best to use the right tool for the job at hand. Now that I have both, I'll always have the right tool for the job.

>In addition to using MoI for boolean-oriented pieces, one other workflow that may appeal to you is to use
> some of the surfacing tools in MoI to create a kind of rough base form quickly, then take that into your
> polygon package and use some of the newish style retopologizing tools to rework it into a sub-d friendly
> form and then continue to work on it as polygons.

Yes, I've seen that functionality in modo (It doesn't exist in 3DS Max as far as I know).
Your idea of knocking up the basic shapes with Nurbs quickly and refining them from there in a polymodeller is great suggestion, one that I'm sure will work well.

>Anyway, sorry that the NURBS toolset did not deliver on what you expected.
> I think it will be a lot more in line with your expectations for the more mechanical type pieces.

For sure.

I guess it seemed like you got jumped on. (seemed? :) )

Passion is a great tool.

you're not unwelcome. There are users here who HAVE worked with those "High End" tools you mention.

I dont think your offending.

Hope to read you around again. Good luck!

Burr

Michael
Thanks for explaination. I'm sure your modelling methodoly will prove quite useful to other users of MoI or nurbs.

>Anyway, just some more information... But you seem to really want to control the edges directly - to build the surface
>directly by controlling all "skin" more directly instead of using intersections, that is certainly more suited to subd instead.

Yes, I'm tyring to build the aircraft to resemble the real thing. To just add a fillet between the fuselage and fin just doesn't work as it in no way would be close to the real thing. If Moi had variable radius fillets maybe you could come closer but I doubt that would look right either. Same goes for the cockpit. It is not a one radius fillet but quite a complex and subtle transition from the canopy to the fuselage that varies along its perimeter. The blends on this particular aircraft are best to represent with swept surfaces or network (as I tried to do). If I was satisfied with a aircraft that vaguely resembles the real thing, yep I could do it with fillets.

The ONLY real solution!

http://store.autodesk.com/DRHM/servlet/ControllerServlet?Action=DisplayProductDetailsPage&SiteID=adsk&Locale=en_US&Env=BASE&productID=103603900

Seriously!----- NOT POLY APPS.

Brian

Hi Kevin,

> Yep, I'm aware of that. I apologise if I have offended Michael or MoI users.

You have certainly not offended me, and actually I thank you very much for putting in a lot of effort into this!

It is not really a goal of MoI to do better than every other single tool out there for every single kind of project.. Not only is that difficult to achieve anyway, but it also tends to make for a complex and difficult to use tool when it tries to combine a whole lot of different areas.

I'm a lot more interested, especially as a foundation, at making MoI do a certain category of things particularly quickly and easily. I don't see it as a weakness - it is a good feature of MoI that it can be a really outstanding tool for the right project.

So it does not really bother me to say that MoI is not the right tool for a particular task. That does not mean that MoI is not good for anything, just not good for that particular thing...

In this case you would really have to change your modeling style to more embrace intersections between extended pieces to make it work with MoI.

The way that you want to work more on the direct skin of the final result for every single constructed piece, that is not suited for MoI. It is certainly a valid way to want to work, and it is helpful for making subtle tweaks and slight adjustments like you want to do. Like I've mentioned, I'd put it in a similar general category to doing faces and organic stuff like that, that is a strong area for the subd approach.

- Michael

>I guess it seemed like you got jumped on. (seemed? :) )

>Passion is a great tool.

>you're not unwelcome. There are users here who HAVE worked with those "High End" tools you mention.

>I dont think your offending.

> Hope to read you around again. Good luck!

Burrman,

Not a problem, I don't feel jumped on or unwelcome.

All I am trying to say is that nurbs has not proven to be the appropriate tool for this particular project.

BTW. I work full time with Autocad 2d/3d (15 years) and Inventor (5 years) in the industrial design field and have also used Rhino before. I'm not a newcomer to solid/nurbs modelling.

>The ONLY real solution!

> http://store.autodesk.com/DRHM/servlet/ControllerServlet?Action=DisplayProductDetailsPage&SiteID=adsk&Locale=en_US&Env=BASE&productID=103603900

> Seriously!----- NOT POLY APPS

Hi Brian
I'm afraid not. I've worked with Autocad full time for the past 15 years. It doesn't have the surfacing tools or meshing tools to create the complex curvature of a car or aircraft accurately like you can do with good polymodeller such as 3DS Max or Modo. It is very good with creating more basic models of building, mechanical assemblies that sort of thing where you can do lots of booleans.

As far as I know one of the more high end nurbs modelling packages is Catia.

Hi Kevin,

> Yes, I've seen that functionality in modo (It doesn't
> exist in 3DS Max as far as I know).

Possibly with Polyboost? I think another option is Silo which I believe has some retopo tools in it and is really cheap and accessible as a companion program.

But yeah this adds another kind of tool into the mix with another skill needed to be learned, that part is not so good but on the other hand that kind of tool can also be useful in pure poly modeling as well.

- Michael