Hi vinced, those are some great suggestions!

But some of them do not really work with the way that NURBS objects are fundamentally constructed.

For example, the way you are talking about adding in points to an "edge", and then pulling the edge around to deform stuff. That is a polygon modeling concept, the way a NURBS solid works is much different from a polygon model.

In a NURBS solid, the edge you see can be what is called a "trim edge" - it's something that marks areas of a surface as being active or inactive (with inactive areas being holes).

But the the thing that actually has points that you would yank around is the surface that the trim edges are living on.

Only in some special cases like a box do the edges and the "underlying surfaces" actually coincide. Once you have done something like trimmed or booleaned one part with another, you end up with trim curves that are not really aligned in any way (in the sense of sharing control points I mean) to the surfaces that they are living on.

It's a much different system than a polygon modeling system - in a polygon system the edge you see is a direct part of the polygon surface and not some separate thing, so with polygons it works better to do things like yank an edge around or add points to an edge, those are the same things as manipulating the polygon surface. But that's not necessarily the case with NURBS.


I've got some illustrations in This FAQ answer, which may help to better describe some of this stuff like an "underlying surface" and a "trim curve".


But basically, if you want to work on things in a polygon modeling type of way, that's something that just does not fit very well with the way that MoI's object system is set up.

So you may ask "why is MoI's object system set up in this completely different way" - well these same things are the reason why other things like boolean operations work so much better with NURBS objects than they do in a polygon modeling system.

In a NURBS modeling system when you trim a surface or do a boolean, the "underlying surfaces" actually stay all the same and only new trim curves are created on the surfaces to create different cuts and holes in them. You can even erase those trim curves later to recover the original underlying surface. It helps things a lot when pieces are cut that the underlying surfaces themselves don't get more complex like they do in a polygon modeler where the booleans have to create a lot more little tiny surface fragments because there isn't the concept of a "trim curve" in a poly modeler.

- Michael

Hi vinced, here's a bit more description on "trim curves" and "underlying surface".

Here I've drawn a plane, using the Draw solid > Plane command:



If you then turn on control points for that plane, you'll see it has 4 points, one point at each corner:



Now I draw in some curves in the middle of that plane:



Now if I trim that plane with those curves, I get something that looks like this:



However, if you turn on the surface control points, you will see that the surface itself still just has 4 points in it at the corners, same as it did at the start. The hole is defined by a set of "trim curves" that are on the surface, but as you can see they can be going in some totally different direction than the surface's own control points.

The thing that controls the actual shape of the surface are the surface control points, the trim edges that you see there are just marking portions of the plane as being a hole. So there isn't a connection from being able to yank on one of those edges and have the surface shape itself be manipulated, you would only be yanking around the thing that marks which parts of the surface are active or inactive.

This is a way different structure than how polygon modeling works.

- Michael

Hi Michael,

thanks for the fast answer. Yeah i think that i don`t really know how nurbs work. Mostly i do not need that knowledge to do great things with them, but sometimes i think it could get faster another way and that seems to collide with the nurbs character.

2.)Ok then it`s better to do it with displacement or modify the object in a PolygonModeler.

1.)What about
a)The box ? That should work , shouldn`t it?
b.)the cylinder? Why doesn`t it have control points? Wouldn`t it be possible to scale the upper part to get something like a cone even with nurbs? I mean i know we have a cone object, but i think it wouldn`t harm to have several ways to achieve things, if it is possible with nurbs?

3.) freeform curves:
Is it possible to edit them and have the points on the curve and not control points?

Another thing. Are there some great tutorials for MOI, not necessarily for beginners. Tutorials that show the workflow of a pro CAD-user with MOI. I have no problems to create complex objects in MOI myself, but as i don`t have a professional background i have the feeling that i maybe miss something.

vinced

Hi vinced,

> 1.)What about
> a)The box ? That should work , shouldn`t it?

Yeah, but most of the time you would want to create models more complex than a box. If I only add features that work on a box it doesn't do a whole lot of good overall.

But actually I do want to add some stuff in the future to enable you to move faces and edges around, but it is not something that is easily set up with NURBS because it requires stuff like extending surfaces and modifying trimming boundaries. It's not like polygons where you can just jiggle the points of the polygons around and have things stay connected automatically.

There is another CAD program called SpaceClaim (http://spaceclaim.com/) which has done a lot of work to edit NURBS models in that way of pushing and pulling faces around. You might check that out if you want to work with that kind of method right now with NURBS models.


> b.)the cylinder? Why doesn`t it have control points?

That's because the top cap is a trimmed plane and not a "naturally trimmed" surface.

This is described in that FAQ answer I linked to above:
   Why does show points work for some objects but not others?


> Wouldn`t it be possible to scale the upper part to get something
> like a cone even with nurbs?

Yeah, that is possibly currently by using Edit > Separate to break the cylinder into individual surfaces, then you would probably want to delete the top cap, and now with the surfaces as individual objects instead of joined together you can use Edit > Show Pts to turn on the cylinder surface's points and select the top ring of points and scale them down.

Let me know if you would like some illustrated steps on how to do that.


> 3.) freeform curves:
> Is it possible to edit them and have the points on the
> curve and not control points?

There is not any way to do this currently, but it is something that I want to add in the future. It may not come until there is some kind of general history editing mechanism in place where you would be able to edit the original points you picked when drawing any object. But we'll see, if that takes too long I may make a special case just for "curve through points".


> Another thing. Are there some great tutorials for MOI,
> not necessarily for beginners. Tutorials that show the workflow
> of a pro CAD-user with MOI.

There are several links on the "Resources" page which has a link on the main web site:
http://moi3d.com/wiki/Resources#Tutorials

Check out Steph's videos, Daniele's lamp video, lyes Ferrari video, etc...

You also might try searching over the web for Rhino tutorials as well.

- Michael

Michael, that`s what i like about you, that you don`t simply say it`s not possible, but that you really think about it .

“But actually I do want to add some stuff in the future to enable you to move faces and edges around”
That is what I want to hear ;). I don`t care if it comes in MOI 5 or 6 as long as you try to implement it.
I am sure that Nurbs are the future of modeling. The only thing they lack at the moment are the advantages of Polymodeling like fast tweaking of faces and edges ect.

By the way the videos they show on spaceclaim are really magnificent. This is the way to go.
Even if we get only some of these features in MOI at some point in the future.

vinced

Hi vinced,

> I am sure that Nurbs are the future of modeling.

Well definitely NURBS are great for mechanical and man-made type shapes. Those kinds of things tend to have lots of holes and cut out portions, and the way that NURBS booleans work is very nice for any kind of cutting or slicing.

Poly modeling is better for more organic shapes like creatures, faces, characters, stuff like that, where tweaking and sculpting things is more important than cutting or slicing.


There is a lot of variety between different kinds of 3D models. Some kinds of models are easiest with one kind of an approach, and other kinds of models work better with a different kind of technology or modeling method.


- Michael

> 3.) freeform curves:
> Is it possible to edit them and have the points on the
> curve and not control points?
>
>>There is not any way to do this currently, but it is something
>>that I want to add in the future. It may not come until there
>>is some kind of general history editing mechanism in >>place
>>where you would be able to edit the original points you picked
>>when drawing any object. But we'll see, if that takes too long
>>I may make a special case just for "curve >>through points".

I would find "curve >>through points" very useful. Any chance for V3 Michael?

Mark

Hi Mark,

> I would find "curve >>through points" very useful. Any
> chance for V3 Michael?

Yeah, there's certainly a chance! It's too early yet for me to be able to make any promises about what will be or won't be in v3 though.

- Michael

"Poly modeling is better for more organic shapes like creatures, faces, characters, stuff like that, where tweaking and sculpting things is more important than cutting or slicing."

For now i agree, but nothing is impossible, isn`t it? You could do the base shape in a nurbsmodeller and then maybe do your detailing on some kind of second layer which is afterwards transformed into a displacement and normalmap.
The great advantage of nurbs is that you don`t have to mess around with a polygonmesh. You can create it after modelling. But in the end to replace polygon-modellers it`s all about tweaking faces, edges and vertices not necessarily on a polygon-basis.
Spaceclaim shows what is possible, but i think it`s only the first of several steps into this direction.

Only my two cents. Don`t really have the knowledge to give an accurat judgement, but my feelings say ->this is the way.... ;-)

Hi vinced,

> For now i agree, but nothing is impossible, isn`t it?

Well, I'm not so sure about that - it may be actually impossible to combine every single conceivable modeling technique and tool into one single interface and still keep it as something that is simple and easy to use.

When you refer to putting stuff on a displacement map on a second layer, do you mean that is something that you'd expect to do all within MoI?

Unfortunately it is very difficult to jam in a zillion features into one program without making the program complex and hard to learn...

In a lot of ways it can help a tool like MoI to be easier to use when it is more focused on solving some particular kinds of modeling problems really well instead of trying to do everything.

Of course I do want to add stuff to MoI to make it do more stuff in the future as well, but that's a pretty tall order to focus on doing every single possible kind of model all in one tool...

- Michael

No that was meant in general not a feature request for MOI ;-)