Hi Kevin, do you have an example of the kind of thing that you are talking about?

Normally the stuff that will work well with NURBS are objects that are much more completely defined by profile curves and do not require tweaks in a little localized area after they have been surfaced.

I mean other than combining components together. In NURBS modeling you can add a detail to a little spot like a knob or something by booleaning a structure into place there rather than moving points around.


There are quite a huge number of objects that are suited to this process... Probably a bunch that you are looking at right this moment like your computer monitor, keyboard, computer case, etc...

But if you are not able to define each component very completely by a set of 2D profiles, then it is likely that a subd type modeler which is very focused on that kind of 3D point cage manipulation would be a better choice for that particular kind of model.

For things that are 2D profile driven, doing those kinds of shapes with NURBS will make the model come together very much more quickly and accurately than trying to push points around in 3D though.

If you have some examples of things that you're having problems constructing with NURBS it would help to give you some more information on a better approach or whether it is indeed a case that should be done with subd instead.

- Michael

Michael

Here are two examples that I could solve if point pulling were available.

1.
Unable to get a straight line for the windshield (see my last post of this thread).
http://moi3d.com/forum/messages.php?webtag=MOI&msg=2020.1
2.
Unable to get a smooth transition at the wingtip from the leading to trailing edge, you get a bit of bump or flat spot where the curves meet at the wingtip. Point pulling could solve this. The bump is not as noticeable on this flat wingtip type but on WWII fighter or a lot of jet aircraft the wingtip is a little chunkier and rounder where the problem manifests itself.
http://moi3d.com/forum/messages.php?webtag=MOI&msg=1762.10&highlight=yes

Other places where it would be useful is wing fillets. It is far easier to define the shape with curves and the create the surface and then use point pulling to tweak it to final shape which you might have to do after trimming if it doesn't looks quite right.

There was also a thread recently where a user was trying to create a curved surface on top of a guiter. That would be easy to solve with point pulling.

Nurbs by its nature seems to create tensions in the surface when lofted or swept which often warps the nurbs surface to bumpy shapes. Your scaling rail option (congrats on this feature) address the problem to some extent but there are many instances when that option isn't available or applicable and bit of point pulling could solve it. This is the main reason I gave up on Rhino a few years ago so point pulling would set MoI apart if it were available.

BTW I think you should give priority to layering and object organisation as for me that is the most needed thing in the software.
The other was construction plane which you've now added to the latest beta (cool !).

Hi Kevin, sorry I missed part of your last message on the canopy thing (did you possibly edit in some more details after your initial post?), I'll head back to that thread to see what was happening there. But basically if you want to get a perfectly flat side view profile, that should be possible by cutting with a line in the side view. That will generate a perfectly flat side profile a lot easier than any point pulling would. Maybe I don't understand what you want there.


> There was also a thread recently where a user was trying to
> create a curved surface on top of a guiter. That would be easy
> to solve with point pulling.

I guess I should have clarified a bit more - as you saw from some of solutions to that, there was some point manipulation happening but it was applied to curves first and once the curves were set up there were plenty of curved surfaces created there...

But first I'll see if I can understand what you were looking for on that windshield.

- Michael

Hi Kevin, I posted some more details on your windshield thread here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2020.11

Maybe I don't understand what you are trying to get there, but as far as I can tell that is a very good candidate for a totally non-point-pulling type approach because if you want a completely flat side profile cutting the larger sheet with a line will give that to you very easily...

The key thing is to allow the cutting operation to generate that flat edge and to build the base shape to be a larger and more simple sheet, rather than trying to draw all the edges first and trying to surface around all of them only in a "piece by piece" type fashion.

If you try to surface around holes it is way more difficult, the natural way to approach these things with NURBS is to build larger sheets and then cut pieces instead.

- Michael

Hi Kevin, just one other note, you wrote:

> Nurbs by its nature seems to create tensions in the
> surface when lofted or swept which often warps the
> nurbs surface to bumpy shapes.

That kind of thing is going to happen to you a lot more often if you try to build directly to every single 3D edge curves of your final result (like what you were showing on your initial approach for that windshield), rather than building larger and more simple surfaces and using trimming and booleans to form the final 3D edges.

I know that it is a bit odd because other styles of modeling do work more directly on placing all edge loops more directly.... But that approach is not going to work well with NURBS, it is not the natural workflow for NURBS.

For NURBS to work well you need to generate broader surfaces that match a more 4-sided topology, then cut away the areas you don't need to form the final edges.

- Michael

Hi Michael

I better clarify a few things
>Hi Kevin, sorry I missed part of your last message on the canopy thing (did you possibly edit in some more details after your initial post?)
I did, but I didn't worry too much about it as I doubt anybody could help me with this one, (see my response below).

>But basically if you want to get a perfectly flat side view profile, but if you want to get a perfectly flat side view profile that should be possible by cutting with a line in the >side view.

Yes that is the only way to approach the problem with nurbs it seems and I fully understand that. The problem that I have is that I'm trying to model the windscreen so it looks like the real aircraft (F9F Panther). That means the flat windscreen shape has to look correct compared to the real aircraft when viewed from the front as well as the side. If I simply cut a line though my existing surface my windshield shape does not look correct. I then have to try and figure out what shape my curves (that I two rail swept) need to be in order for the windscreen shape to look correct when I cut a line in the side view with a straight line. Also trying to figure out exactly where that staight line needs to be in the Z axis would be a trial and error process. This is a geometric puzzle. I hope my explaination makes sense to you and you understand why I was approaching the modelling of this object the way that I did originally. If I was modelling a fantasy spaceship or aircraft of course none of these things would matter.

I'll try and post up a better wingtip example for you as it will clarify better what I was talking about.

Hi Kevin, it would probably help quite a lot if you could post some pictures over in that thread (especially close-ups of the canopy) of the real shape.

Otherwise it is just hard for me to understand exactly what you mean by "flatness" or make it look right from the front, etc...

It sounds a bit like you may want to focus more on adjusting the shape of that centerline scaling rail curve to fine tune the shape that is generated.

Definitely though just drawing contours of irregular topology and trying to surface directly to all of them as exact edges of sweeps or networks usually does not tend to give the best results.

- Michael

Michael

I've posted the wingtip problem here http://moi3d.com/forum/messages.php?webtag=MOI&msg=1762.1

Like I said, I almost get what I want with Nurbs and if I could point tweak I could probably fix it.

However, I might have modelled the wing in a bad way so am open to suggestions on how it would be best to tackle this part ?

Hi Michael

This was the other issue I was talking about with nurbs where tensions get created in the nurbs surfaces warping it from the shape you want. Having the ability to tweak points would allow the user to fix this.

Today, aircraft are designed with NURBS. Fantasy aircraft and unrealistic objects are modeled by Poly and SubD.

If this aircraft were being modeled TODAY, it would be done with NURBS.

I'm sure it would but I still can't get the shapes I want as you can see from my last post.

Hi Kevin,

> This was the other issue I was talking about with nurbs where
> tensions get created in the nurbs surfaces warping it from the
> shape you want.

Yeah this kind of thing will tend to happen if you try to build a single surface that goes through significant changes.

One thing that could help in this situation is to separate this out into smaller pieces - one piece for the main fuselage that goes more evenly towards the back and then have the tail fin as a totally separate part that then gets booleaned or trimmed to mate with the main fuselage and then a fillet or blend put in between them to make a smooth juncture.

Trying to make a large protrusion as a single surface construction will be much harder to control than building in smaller pieces.

The kind of tensions that you are showing here are basically the result of one profile transforming into another one, probably you don't like the default mapping or connections that are being used between each profile. You can get some more control over how the profiles connect to one another by using Network and putting in some more section curves, that can let you kind of control the connections some more.

But really I would think building in more simple pieces, one for the main body and the tail fin as a separate piece would be more of how I would go.


> Having the ability to tweak points would allow the user to fix this.

The ability is actually there - you can select the surface in your example there and use Edit/Show pts to turn on control points. Then you can select a point and move it around to deform the surface. But in MoI this does not tend to be a very big focus of the toolset. If you want to model by tweaking the surface mesh points more directly probably you should be using a subd modeling tool instead.

- Michael

>But really I would think building in more simple pieces, one for the main body and the tail fin as a separate piece would be more of how I would go.

Yep, it seems it is the only way (pretty much like the real aircraft in fact). I try to avoid doing this though because it is much harder to sent up geometry wise and you tend to end up with meshing flaws once exported to a polymodeller. Even though meshing in MoI is far better than Rhino it still has its problems at joints and I really want a nice smooth clean mesh.

Hi Kevin - re: nice smooth mesh - if the problems you are seeing is a lack of smoothness when importing into Max 9 in particular, that may be greatly helped out by getting the updated FBX import plug-in.

If all goes well, that should enable you to get the accurate surface normals transferred over and have those used for shading the mesh in Max.

When you get the accurate vertex normals it really makes for a much smoother shading and it can pretty much eliminate the worrying about how the mesh is specifically arranged.

This has been a big problem specifically with Max because unlike other programs it does not seem to like to read this information out of other formats such as OBJ format.

The main reason why I wanted to do the FBX export was to hopefully get rid of this exact problem.

- Michael

>if the problems you are seeing is a lack of smoothness when importing into Max 9 in particular,
> that may be greatly helped out by >getting the updated FBX import plug-in.

That is fantastic news as that is the main reason I gave up on Rhino in the past was inability to create a decent mesh from all the surfaces.

I've downloaded the latest FBX plugin for Max 9 so, I'll give it a go and let you know if it gives better results.

PS Max seems to import OBJ format just fine. The messy mesh joints occur in MoI and Rhino. Both programs have trouble stitching the mesh together at the nurb surface joints. The problem is much less in MoI compared to Rhino.

Hi Kevin, well if the joints do not look right in MoI then the FBX export is not going to help with that particular problem.

If you have an example of that it could help if I could see it.

But my guess would be that you had an export where you had 2 surfaces that were separate objects that were sitting next to each other, rather than having them joined together to be a single connected object.

You need to join surfaces together to have shared edges before you export - if you don't they get meshed individually without any awareness of each other and they can get slightly different vertex structures along their adjacent edges, creating small gaps or cracks.

When they are joined together to be part of one larger object that has shared edges, the edges will be treated with special attention to have a fully compatible vertex structure along the shared edges, so no cracks or gaps will happen there.

So be sure to use Edit/Join to glue surfaces together to have shared edges before you export and that will solve that problem, if that is what you were seeing. That applies to Rhino and MoI both actually.


> PS Max seems to import OBJ format just fine.

Sort of - I mean it brings the polygons over but did not seem to bring the vertex normals over, so it calculated shading by averaging polygon normals together instead of using the true normals that come from the original NURBS surfaces. When shading is done with the true normals it eliminates a lot of shading artifacts and gives a much smoother appearance.

- Michael