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

Hi Kevin,

> If Moi had variable radius fillets maybe you could come closer
> but I doubt that would look right either. Same goes for
> the cockpit.

Variable radius fillets will definitely get in here at some point, it just has not quite bubbled up to the top of the list yet...

Another approach which can work for this is to trim the parts back so that there is a gap between them, and then use Blend to make a smooth juncture (G2 option in blend). That is a lot more of a "natural" and seamless type of juncture between pieces. You can kind of get a similar effect as variable radius fillet by varying the width of the gap that is trimmed between the pieces.

But that is getting into much more of the fancier and advanced part of the NURBS toolset, kind of away from the easier and quicker parts.

Probably the best result for the kind of highly controlled blend that you are describing would be trimming a gap and then doing a 2-rail sweep with some custom profiles to shape the blend, with an option to force the sweep to be smooth to the edges it is sweeping along. MoI does not currently have this option, but it is another piece that I want to add in eventually... Again it is part of a kind of advanced toolset so it just has not been a focus for the earlier part of MoI's toolset.

- Michael

Since this is a learning thread, here are some points.

The detail to the creation is "KEY". If you examine the curves of the model that didnt work you'll notice these sharp "CORNERS" that dont exist on the REAL object surface. It may appear to be a sharp spine in a picture, but if you put your hand on the surface of the F9F, you'll not feel this sharp edge.









The precise nature of NURBS calls for extremly accurately placed points and curves. If this is not done accuratly, then the results will be according.

Kinked curves produce kinked surfaces! this model has designed kinks all over it.

If we look at the software capabilities for Complete accurate depiction, yet Rhino falls short then what are we doing?

It seems there is an opposite conundrum here in that, NURBS would do the REAL object and Poly can easily replicate it to look somewhat real. Not the other way around.

BurrMan

>Kinked curves produce kinked surfaces! this model has designed kinks all over it.
Please reread Michael Gibsons post 20 and 27. It explains why my surfaces have warped and twisted all over the place and have not given me the results I wanted or expected.

> Probably the best result for the kind of highly controlled blend that you are describing would be trimming
> a gap and then doing a 2-rail sweep with some custom profiles to >shape the blend, with an option to
> force the sweep to be smooth to the edges it is sweeping along. MoI does not currently have this option,
> but it is another piece that I >want to add in eventually... Again it is part of a kind of advanced toolset
> so it just has not been a focus for the earlier part of MoI's toolset.

This is what I have done in my model except the swept surface doesn't have the ability to maintain a G1 or G2 tangency blend with its adjacent surface (limitation of MoI and last time I used Rhino it didn't have this feature either). Even if it did I'm not sure if my surface will still buckle and twist due to the cross section transitions I need the nurbs to make.

Not to worry though, I'll keep on eye on MoI's future development and like I said will still be using MoI for the detail components of my aircraft where booleans are far easier to do than polymodelling them.

Hi Burr,

> It seems there is an opposite conundrum here in that,
> NURBS would do the REAL object and Poly can easily
> replicate it to look somewhat real. Not the other way around.

It's pretty much a non starter to use polygons/subd for the "master definition" of an engineering model, because they are unable to represent conic section shapes like circles, spheres, cylinders, etc... You can get closer and closer to a precise sphere shape by using a lot of points, but it is inefficient to use a lot of points and still does not get a perfectly defined sphere. This is really bad for mechanical parts which tend to have lots of things like circular holes in them.

So that's the fundamental reason why NURBS is used for the "real" engineering tasks - it is a kind of unified object definition that can have exact circles, or also wiggly surfaces not just only one or the other.


Polygons in their simplicity though do give an easy ability to tweak and edit them, you are more free to grab a point somewhere in the middle of your shape and pull it up a little bit, or widen a piece a little bit by yanking points around.

The NURBS toolset does not tend to work like that and instead has more of a "construction" approach with building surfaces from drawn curves, booleans, cuts, fillets.

If you want to work more of in a "sculpting" type way of kind of nudging and tweaking your surface, then polygons work more for that.

If you want to work more of in a "drawing" type of way where your pieces are more defined by profile curves and you want to have things like fillets where pieces join, then NURBS works more for that kind of thing.


A lot of times organic modeling for stuff like faces and characters fits more with the "sculpting" method and mechanical and industrial type shapes fit more with the "drawing" and profile driven method.

An airplane fuselage and a car body are examples of man made objects that have a much more organic shaping to them, that can sort of put them on the "sculpting" side of the fence moreso as far as what is easiest to mess with them.

No matter which one is easiest for an individual person trying to whip out a particular model for rendering, for actual engineering "master plan" data the NURBS method is always the one used because it has that ability to have stuff like exact circles.


People build models for all kinds of different reasons though, if you're rendering the object and not constructing it, it is probably not a problem to you that your sphere is 0.05 units deviated from a true sphere because it is hard to see that in the rendering.

So the right tool for the job depends on a bunch of different stuff - what your goal with the result will be, etc...

- Michael

Hi Kevin,

> This is what I have done in my model

No, not quite - what I was talking about there would be using the kind of "larger independent component" parts like I was showing earlier. You were mentioning that a fillet would not do the right thing that you wanted where the pieces connected - you would use a sweep in there instead of the fillet, kind of like this:

The 2 larger components booleaned together:



Then since a fillet does not give you the right shape, you would trim away some parts to make a gap:



Then the sweep would fill in that gap making a kind of custom fillet - the sides of the gap would be the rails for the sweep and you would put in some cross-sections to control the shaping of the blend to get more control over it.

That would be the way to solve your problem of a standard fillet not being what you wanted in between those 2 pieces. But it will be a while before that would work with continuity in MoI.

- Michael

Thanks Michael

I understood what your meant even without the images or extra post and thankyou for you help and advice. This is pretty much how I have gone about creating the fin and cockpit in my model. I've booleaned off the areas of the aircraft where the fillets begin and used curves to define the ends but the transitions of the curves are just too tough for nurbs it seems and results in a lot of surface joints that look bad on the meshed model.

I still leave it open to Burrman, Brian or anybody who wants to have a go to show me how this aircraft should be done with nurbs. I would be most interested to see their effort and how they went about it. All the reference photos they need, blueprints and MoI setup is contained in the first post of this thread. My only requirement is that they closely capture the look of this aircraft as it easy to distort the shape of the aircraft to suit the software.

The challenge is there and there is no time requirement

Hi Kevin,

> This is pretty much how I have gone about creating the
> fin and cockpit in my model.

Is that in a version that you did not post any screenshots of?

The reason why I ask is the last one that I saw was this:




That one is definitely not done in the same way, again the difference is an edge-to-edge type construction there rather than building separate parts that intersect one another - that is that punch all the way through each other.

At any rate, the actual method that I was describing is not possible with MoI yet, I'm talking about a way that would be possible in the future with some enhancements to the sweep command to ensure continuity. It would be what would be needed to use instead of the fillet for joining the "solid" components together since you don't want a standard fillet there.

- Michael

Michael

Yes that is correct, this is the last image I posted and its current stage of construction.

I've created a series of swept surfaces to try to recreate the complex shape of this area (Unsuccessfully).

Your last post also needs the user to create a swept surface to create the subtle curvature around the cockpit.

For anybody who wants to have go modelling this aircraft and has difficulty understanding what shapes need to be created I attach a polymodel version of the fuselage. Perhaps these images make it more clear of the complex curved surfaces involved around the cockpit and fuselage/fin blend. As you can see it is not a one radius fillet but a series of complex curved surfaces that all seamlessly blend together.

Seeing this was my very first, ever, plane model I was pretty pleased with my 75 year olds new MoI skills.

Had fun anyway.

Brian

Hi Kevin, I wish I had enough time available to work on all the small details that you're really interested in. But unfortunately it is just not going to be feasible for me to spend much time on this.

But here is generally what I would probably go for with a NURBS approach:





Model is attached as PantherNURBS_3dm.zip .

I fully understand that this does not have many of the details that you need, but it may give you some ideas of what could be possible.

But I don't think though that there is really any good reason for you to switch off of your polygon modeling workflow for this task. At the level of detail that you want to achieve, I don't really think that you are going to gain any benefits by trying to do it with the NURBS toolset, there are a lot of detailed things and problem areas that you would have to sort of navigate through. If you didn't care so much about the specific details you could possibly get a speed boost for this but with the target that you have in mind I think you'll be looking at decreased speed for this particular type of task. And that would be after a ramp up period to get accustomed to a different toolset. It does not leverage the "sweet spot" of NURBS that would deliver a speed increase for things like heavy booleans.

At any rate, you can see the results here of some of the more component based structuring that I was referring to earlier, and can at least show that you can get good surface quality with the right kind of strategy.

- Michael