Hi Michael

To some extent when modelling anything you have use a panel by panel approach. Why am I doing that ?

The answer lies here in your own statement
>It may require you to do things like subtle edits and visualizations of how pieces intersect before you get a good result.
It is pretty darn hard (impossible) to visualise what shape the canopy needs to be so that when the windscreen is booleaned from it that shape matches the look of the real thing or plans. Where it is far more logical to create the windscreen shape, get it to look right by tweaking curves and then create the canopy shape from there. Which as we have seen doesn't work. And yes this is also how I would do it with polys except this approach does work.

The other reason is that the plan view & side view shape of the cockpit opening and windscreen are known entities from the plans so I am trying to model up to those know entities. What are not know entities are all the subtle blends that lead to those items which can only be done by eyeballing the shapes from photos. The plans are not much help when it comes to the shape of all those blends.

>I mean you can clearly see that the overall form that I created there does not suffer from bunching or warping issues.
Yes, I can see that the way you have tackled the transition of the fin from the fuselage is a good approach much like polymodelling.
But trying to get the shaped pulled to match the airfoil shape of my fin would be almost impossible to do on a first attempt. Once I've trimmed it so I can see what cross section shape I have got, I can't change it ? I would have to undo, trim again, nope still not right, undo, tweak, trim, undo, tweak trim undo etc. Bit of nightmare for someone trying to model this thing accurately. Sure if you're modelling fantasy stuff, who cares what shape it is.

As I stated in Jasons Clarks thead, nurbs almost gives you the shape you want but without the ability to tweak those surfaces to get those surfaces looking right compared to your reference photos, the user is in for a lot of trial and error and a very frustrating time. But as you've said if it were possible to do this, all your joints would start springing apart.

So this all comes back to the wrong tool for the job at hand. Best to use nurbs for what it does best which is boolean operations of more mechanical type parts rather than the complex curvatures and blends associated with trying to accurately portray a real car or aircraft.

Michael
I feel we are both going around in circles. Your telling me how nurbs works and how I should model. If you feel your not getting through to me your wrong, I fully understand exactly what your saying. For the reasons I mentioned above (please read them carefully), I'm sorry that approach is beyond the average modeller or even the above average modeller who wants to model a car or aircaft accurately which is probably the reason there are so few Nurbs cars or aircraft that are accurate looking representations of the real thing. All this work being done with polys. I honestly wish this was not the case as I like the precision and speed of working with nurbs but unfortunately for projects like this trying to get nurbs to bend to the complex curvature of this aircraft is just too difficult and time consuming for the average modeller.

Aside from solving all the modelling problems, getting your nurbs model to good clean mesh ready for uvmapping and rendering is another whole set of problems.

Hi Kevin, sorry I haven't gotten the other kind of strategy explained clear enough yet.

> To some extent when modelling anything you have
> use a panel by panel approach.

No - maybe the confusing part is that the final result of all methods will result in a side-by-side set of panels that have shared edges.

But there is a big difference between trying to build a skin of surfaces by a totally edge to edge construction (which is not a good strategy for your desired smooth skin result) or by first creating components that are extended surfaces that do not share direct edges with neighboring pieces until they are intersected with them.


> Why am I doing that ?

Because you are trying to build a surface directly following the edge of another surface, instead of as parts that punch through each other.

Here I'll try to explain it more clearly. This is a screenshot of one of your previous models that you posted:



Here are a couple of surfaces colored in:



Notice how you have constructed the green and blue surfaces so that they are following the same boundary edge as part of their initial construction - they do not push through each other instead you are trying to build them in an edge-to-edge manner, similar to the way that panels touch each other edge to edge tiling an area, hence the description of "paneling".

That is not a good strategy for trying to make a broad smooth skin with NURBS.

Instead a completely different strategic approach is needed, which is to build components that are initially completely separate objects that push through one another and are not constructed based off of a common boundary.

I was trying to illustrate that method with those previous steps, here is one key part:

In the steps I showed, notice how the canopy is a completely independent assembly, it was built off of "self contained" reference curves and not attempting to ride along the boundary edge of another piece:



The 2 pieces do not touch edge to edge yet, they punch all the way through each other:



They do not share an edge-to-edge common boundary until you trim them to one another. That is why they are not like the paneling method that you were using, which instead tries to build surfaces directly to a common 3D edge curve. Again that method is not the right strategy to use for making smooth skins with NURBS.


> It is pretty darn hard (impossible) to visualise what shape the
> canopy needs to be so that when the windscreen is booleaned
> from it that shape matches the look of the real thing or plans.

It is not impossible, it is a skill that may take time to develop. But it is certainly valid if you do not wish to develop that skill and find it easier to use the subd type method instead, I agree with you that your current method is an easier and faster method for the way you want to edit and tweak things.


> Where it is far more logical to create the windscreen shape, get
> it to look right by tweaking curves and then create the canopy
> shape from there.

I don't agree - to me the overall shape of the canopy is the sort of "primary" outer form that you would want to shape, and the windscreen is a cut out smaller subcomponent of that.

With NURBS I would usually work in that kind of a way, focusing on major forms first and putting in small details later which get merged into the main pieces by trimming or booleans.

It is definitely a very different approach than what you are used to with polygons, so it is not surprising to me that you would not like to work that way.

It does not however mean that it is an "impossible" way to work at all though.


> I would have to undo, trim again, nope still not right, undo,
> tweak, trim, undo, tweak trim undo etc.

That is not the only option available - you can also use Construct / Curve / Project to project a curve onto the surface, when you edit the surface you will see the projected curve update dynamically with your edits so that could be a more convenient system than what you describe here.

But really the main thing is getting used to the process so that you have more of a good anticipation for how the projection is going to look, with more experience it gets to be a more natural process.


> But as you've said if it were possible to do this, all your joints
> would start springing apart.

It would be if surface control point editing was the only way to do edits. But the more typical way from a "construction" type workflow would be to instead edit the input curves that went into the sweep or revolve, etc.. to tweak the shape. When I was talking about tweaking the canopy that was the kind of editing that I was thinking about, sorry I did not make that more clear.

Surface control point editing is also available and can be helpful to kind of make a slight adjustment in an already close surface, that is what I was using it for in that one stage in my previous illustrations, I probably would not use it though for tweaking the canopy.

I do not disagree with you that it is much more difficult to achieve a smooth skin type model using NURBS instead of polygons.

Doing it with NURBS tends to require a particular strategic approach, which is what I have been trying to describe. It is definitely more difficult to learn this approach, which is easy to see since my descriptions of how it is different than how you tried originally or what "paneling" is do not seem to be getting through.


None of these several past explanations have been intended to convince you to switch to a NURBS based workflow, they have just been an attempt to show you what kind of strategy would be required in order to use NURBS. The strategy that you were originally trying to follow in your initial posts is way different from that.


Anyway, you definitely do not seem to like the strategy that would be required for NURBS and I don't blame you - the way that subd works is definitely easier for making a totally smooth skin that has various protruding kind of bits with a kind of "melted together" type blending going on everywhere.

Since it is not something that you are going to want to switch over to, I think I'm going to stop trying to explain it over and over again.


> Aside from solving all the modelling problems, getting your
> nurbs model to good clean mesh ready for uvmapping and
> rendering is another whole set of problems.

Did you notice PaQ's previous post just earlier today that had a good clean mesh and uvmapping?

http://moi3d.com/forum/index.php?webtag=MOI&msg=2039.8

- Michael

With a little research, shows you have been makeing this same post since at least 2006.
Forum posts from you stating how making an aircraft "TRUE" has to be done with poly modeling due to the shortcommings of NURBS.

Whats the agenda here? It really is a belief you hold close and wont let go of.

Burr

Ahhhhh!!!

Still 4 years (decades in 3d time ) behind in modelling app theory/application?
(And, also, STILL!, Lightwave can not handle .obj files properly!)

What we know about Poly modelling is , even now?, left in the dark ages by what is happening in the latest Alpha/Beta version of 3D Coat--NOW, that really is a different WHACCO!

Brian

PS Complimentary to MoI!

Sort of?

Brian

Hi Michael


I know this functionality does not exist in MoI and last time I used Rhino it doesn't exist either.
Once a surface is created, say a swept surface and then trimmed.

Is it technically possible to in some way let the user define how many points make up the surface. If there were less points it would be more artist friendly because there are two many at the moment to manipulate the surface unless you wanted to add a small detail to it. Or could something like 3DS Max's FFD modifiers be programmed into the software. That would then allow the user to manipulate the surface and kind of mould the shape they want. Just a thought anyway. I'm thinking if it had that functionality I could probably mould up the upper surface of the aircraft.

>That is not the only option available - you can also use Construct / Curve / Project to project a curve onto the surface,
>when you edit the surface you will see the projected curve update dynamically with your edits so that could be a
>more convenient system than what you describe here.

That is the answer I've been looking for. That will give me a kind of cross section tool that will allow me to see what shape I will get before I boolean. Hopefully this will also work on the point pulling exercise you showed for the tail section. If it does then I can now have another crack at this project.

Hi Burrman

Thanks for your post.

The reason I started this thread was at Michaels request. See post 20 of this thread http://moi3d.com/forum/index.php?webtag=MOI
He asked if I would show him some examples of the kind of things I was referring to. I decided it might be best to put all those examples in the one thread rather than scattered around the forum.

My agenda with this thread is as follows
1. Create an accurate looking F9F with nurbs and export a mesh out to 3DS Max for texturing and final artwork.
2. Learn more about MoI and Nurbs surfaces.
3. To show Michael some of the problems users face when modelling up difficult subjects which may help him (it may not) further develop the software.

Hi Kevin,

>>My background is Autocad and Inventor which I use all day, everyday at work for past 15 and 5yrs. Both those programs would be totally unsuitable for a project like this or to model up a car. Both are great for architectural and mechanical type work though.

Aircraft/cars are mechanical, so dont quite follow your statement. I cannot comment on "inventor" as I have not used the program, but Autocad, I have used many versions over the years for aircraft and F1/touring car work.

>>At first I tried Rhino V2 and V3 but found getting a a good clean mesh from that program problematical. The problems are mostly bad mesh at the joints between the surfaces which creates shading errors when rendering the model

That is final output and not related to internal construction, and it is mainly construction problems you have posted about.

>>I will be most interested to see your attempt at the model and I appreciate you taking the time to have a go.

Unfortunately I have had no spare time to look at this, but I am unsure of your exact problem. Is it with construction (which should not really be a problem with your use of autocad), or is it just the poly output after construction (in which case whatever method of construction is used, there could still be the poly problem).


- Steve

Some interesting stuff I found if of interest to anyone.
Brian

http://pubs.drdc.gc.ca/PDFS/unc48/p521647.pdf

http://www.google.com/search?hl=en&rls=com.microsoft:en-au&q=Modeling+an+Aircraft+in+Nurbs&start=10&sa=N

http://www.icon.fi/~jtki/3dimens.html

http://ogigi.polsl.pl/biuletyny/zeszyt_14/z14cz3_6.pdf

Hi Steve, thanks for your post.

>Aircraft/cars are mechanical, so dont quite follow your statement.
> I cannot comment on "inventor" as I have not used the program, but Autocad, I have used many versions over the years for aircraft and F1/touring car work.

I'm not talking about using Autocad (or Inventor) to draw up the components of the car as I know both are used for the that purpose all day every day right around the world. I was referring to using Autocad's 3d modelling tools to create the aerodynamic shape of this aircraft and all the subtle blends around the upper part of the fuselage and fin and then converting that model to a nice mesh from Autocad. Autocad's surfacing tools are a little on the primitive side compared to MoI and Rhino.

>That is final output and not related to internal construction
Yes the mesh is a seperate issue and nothing to do with constructing the model in the first place. I suspect Michaels work on the FBX plugin will largely resolve a lot of my past meshing issues especially since I use 3DS Max.

>Unfortunately I have had no spare time to look at this, but I am unsure of your exact problem.
Where I am having problems is creating the blends that are around the cockpit and upper part of the fuselage as shown in the photo of post 63 of this thread.
The rest of the aircraft I should not have any problems with.
What I was hoping you might be able to help with is the best way to tackle this area and keep the blends that are created tangent to one another so that I get nice smooth highlights on my aircraft when rendered.

Hi Kevin,

I'm following this thread, and I understand your filling, I'm coming from more of 10 years of poly/sub-d modeling and I discoverd nurbs this year with MoI.
So far I never had to build something 100% real, so I always find some workaround or 'design' change because I can't exactly get the base shape I want.
In the other hand, as you probably know allready, when the base shape is done, adding all the details is really fun with nurbs, and much more productive than poly modeling.

Maybe you should give a try to T-Spline for rhino and maya. I didn't bought (is that the right spelling ? :P) it yet, just did some easy test with the demo edition. I suppose if I have to build something more advanced with a really organic base shape, I will certainly use this tool. T-spline provide a lot of tool, the best one (for me), is to be able to translate a sub-d cage object into a nurbs version. I don't know if the output quality will be enough for what you are looking for, but maybe it's a solution to help the transition.

http://www.tsplines.com/

Here's for example the modo old guy head in MoI
http://moi3d.com/forum/get_attachment.php?webtag=MOI&hash=b952bf93a30a94269695bbcd2f01caae&filename=wow4.jpg

I don't know howcomplex the technology is, but if one way or an other we can have this kind of feature natively in MoI, (importing a obj cage and get the sub-d version in nurbs) ... that would be realllllly amazing !!!!!!

*edit: Just discovered that Maya allow natively to convert suv-d in nurbs too (I'm only learning it since yesteday :) ... now have to inverstage what are the export format available to get the model in MoI :P

for the old guy is that the process?
Modo OBJ -->Tspline -->Nurbs --> MOI

Hi Paq

Thanks for you comment and interest in the thread. I know there has been a lot of discussion in this thread but I hope there are solutions presented here by Michael that will help people solve some of their more advanced nurb modelling tasks. Unfortunately for me so far on this particular project I haven't been able to achieve what I want.

I had a good look at tsplines yesterday and believe that it would be the best way to tackle the upper part of the fuselage of this aircraft and also give me a nice mesh. It would allow me to kind of sculpt up the shape I need as I am unable to get nurbs to conform to the shapes I need via converntional sweeps and networks especially since surface tangency options are somewhat limited.
Unfortunately the cost of buying tsplines and Rhino for my hobby is a little prohibitive but like you I hope that one day this tool will be standard in nurbs packages as I believe it would be of tremendous benefit in instances like this and many others that I can think of.

>So far I never had to build something 100% real, so I always find some workaround or 'design' change because I can't exactly get the base shape I want.
Yes, I am having similar issues except I don't want to change the design. I want to capture the look as closely as I can.

>In the other hand, as you probably know allready, when the base shape is done, adding all the details is really fun with nurbs,
>and much more productive than poly modeling.
Absolutely, totally agree 100%. It is not much fun cutting out holes, vents and openings in meshes, very tedious work.

Yes Pilou,

I used t-spline for rhino,

So in rhino you import the obj as an sds cage with the tspline plugin (not with the rhino obj import of course), t-spline create a t-spline version of the cage ... then convert it in nurbs, and save it in .3dm.

There was also an tool in the t-spline toolbox you have to use to smooth the blending between every patches. (I don't remember the name)


Now again, until one hour ago, I was thinking that the sds->nurbs was only possible with this t-spline plugin ... but if maya can do it natively, we maybe don't need an alien technology to get the same thing in MoI ... crossing fingers :o)

If of interest
My second go at an aeroplane--all imagined!

Hugely faster than my first effort in MoI but still did some things in silly ways which I would not repeat in a third effort.

Pretty rough I guess--but very, very quick!
Saved to both FBX and ObjN-gons from MoI to use in Carrara.

Brian

Here's a sub-d sphere (aka a box :P), exported in .igs and timmed/filleted in MoI. Need to do some advanced test too :P
Happy me I have to lean and use Maya in my new job :o)

Here's a other try using maya, still thinking it might be a cool way of working ... however there as some areas that are quite
complex (red lines) and need probably to be rebuild/simplify too.

Maybe a little polymodeler in Moi ? :D

Hi all,

Testing some neat stuff there guys.

- Pilou -> Nah Moi is a nurbs and for myself i would love that he stay like that (Michael decide anyway). I have enough modeller with Carrara, Hexagon, Cinema 4D that i added Moi because of the NURBS.

Hi Kevin,

You wrote:
> I know this functionality does not exist in MoI and last time
> I used Rhino it doesn't exist either.
> Once a surface is created, say a swept surface and then trimmed.

MoI does not currently have anything to insert new points into an already existing surface directly, but Rhino has had that function (InsertKnotSrf command) since the Rhino v1.0 release. So that is probably something that you just did not know was in Rhino. That is understandable since there are so many functions in Rhino it can be difficult to learn them all.

I do expect to put this into MoI as well, just the surface control point manipulation toolset has not been a major focus for the earlier versions of MoI since I generally expect that someone who is very interested in pulling surface points around would want to use a subd modeler for that type of thing instead since those programs are totally dedicated to that kind of workflow and are handling that type of thing very well already.


> Or could something like 3DS Max's FFD modifiers be
> programmed into the software.

Yeah, I think that this will be able to happen eventually. But it is not an easy task to make this happen on solids that have joined edges at trimmed surface edges, instead of the natural surface edge of the underlying surface. The latest Rhino version 4.0 has added some various functions to do this kind of thing, so if you want to deform NURBS models with cage editing, you could look into using Rhino for doing that.


Please understand that I only have so many hours in the day to work on MoI. It is just not possible for every single conceivable feature across every single conceivable style of modeling to be added into MoI all at the same time. Many things will take some time to add.


> My agenda with this thread is as follows
> <....>
> 3. To show Michael some of the problems users face when
> modelling up difficult subjects which may help him (it may not)
> further develop the software.

Definitely not a bad plan, and I appreciate the effort!

However, just to be clear, I am already completely aware that MoI's current toolset is not as good for making "point squishing" type editing directly on surface/solid models as you would do in a subd modeler.

It has actually been an intentional design decision to focus priorities in MoI on areas that are not exactly the same as other programs. That can help people get a more well rounded toolset so that they can get more of an expanded toolset when using MoI along side of another program, rather than trying to do a kind of half-effort on duplicating things that are already handled well in your other software.

Over time I do expect to fill in more of the kind of toolset that you are asking about with point squishing, but since it is working well for you in your other modeler, that is all pretty much going as intended currently for the early versions of MoI.

It is the general intention that you would use your other software to do the tasks that suit it better, instead of trying to do those in MoI.

- Michael

Hi PaQ,

Yeah that ability of Maya to transform subd to NURBS does not seem to be very frequently mentioned or used for some reason. But it could definitely be a useful transfer method.


> Here's a other try using maya, still thinking it might be a cool way of
> working ... however there as some areas that are quite
> complex (red lines) and need probably to be rebuild/simplify too.

That kind of smaller patch refinement will generally happen in areas where you have a vertex with a valence of other than 4, meaning more than 4 edges radiating out from it.

Like in this case you seem to have a kind of edge loop that terminates here:



So that created a vertex there that has a valence of 3, and the one right above it has a valence of 5 with 5 edges coming out of it - if you can avoid those where possible then it will probably eliminate that kind of patch refinement.

Like in your case here if you continue that edge loop to the end instead of terminating it, that will probably get fixed up.


There is a common relationship between some of the mechanics of how NURBS surfaces work and how subd surfaces work.

The way that Catmull-Clark subd works, it is actually completely equivalent to a NURBS surface in areas of the subd that have quad polygons with all vertices of valence 4.

Those areas of the subd surface have an exact and natural translation to a NURBS surface.

Areas where that is not the case like at your valence 5 spot, do not have a natural equivalence to NURBS so those areas get processed with a kind of fitting or refinement type scheme to get some NURBS surfaces in there that are close enough to the subd surface. But the refinement will generate additional surfaces, that is what you are seeing there.

- Michael