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