General considerations - Rebuild -Rail revolve - 3D navigation - Deformation tools

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 From:  Artaud (PIETRO)
2285.1 
Hi everybody,

I am just finishing my first MoI model. It is a Fender Stratocaster guitar.
I have chosen this subject to test the different commands and features of MoI. In general, I am very satisfied. Construction lines are precious, the workflow is very simple and fast, working with antialiased lines is very comfortable.
Anyway, respect to other modeling softwares, I found some difficulties in these areas/commands:

- I did not found a "curve/surface" rebuilding tool. Sometimes, it is necessary to simplify a curve or a surface, reducing the number of control points;
- Rail revolve seem to work only with 2D rails;
- with complex shaded models, directx is not so fast. 3D navigation is slow.
- Some deformation tools would be useful.

What do you think about? Did you found any workaround to supply to the lack of some useful tools?

Thanks,
Artaud
















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 From:  BurrMan
2285.2 In reply to 2285.1 
Artaud,

On a side note, Regarding construction lines, There is a script that allows you to "keep" them around for longer than the current operation. If you havnt seen this, you should check it out. "Petr's Moi Page" from the "Resources" tab on The MoI home page:

http://kyticka.webzdarma.cz/3d/moi/

Its an inline script. Look at "CLine" link.

Nice work!
Burr
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 From:  Artaud (PIETRO)
2285.3 In reply to 2285.2 
Thank you very much for this script! My thought is that Clines are really useful!

Artaud
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 From:  Michael Gibson
2285.4 In reply to 2285.1 
Hi Artaud, wow that is a fantastic result for your first MoI model, it looks really great!

I'm glad that the workflow is good for you!

Your questions:

> - I did not found a "curve/surface" rebuilding tool. Sometimes,
> it is necessary to simplify a curve or a surface, reducing the
> number of control points;

Yeah this is definitely on the list to be added, I just have not quite had enough time to get to it yet.


> - Rail revolve seem to work only with 2D rails;

The way that rail revolve works is by a kind of scaling out from the center axis, I'm no so sure that it is really well defined on a non-planar rail.

If you could please post some example models that are using a non-planar rail from other software that would help me to see what you are looking for more specifically and what might be possible here.

I do want to add another option for rail revolve in the future to make it work with multiple profiles which will use a somewhat different mechanism which is more like sweeping rather than the "exact" combination of 2 curves that the standard rail revolve (sometimes called "swung surface") uses. That method will probably work more easily on non-planar rails rather than the exact method.


> - with complex shaded models, directx is not so fast. 3D navigation is slow.

This doesn't really have a lot to do with directx, but rather the meshing settings.

By default MoI is set to produce a dense display mesh which makes for a very smooth look in the viewport but which will generate a really large number of polygons if you have many small curved parts, especially stuff like long twisted skinny tubes like you've got in your model here will generate a really really large number of polygons with the default settings.

You can switch the settings to be better for a heavier scene by going to Options / View / Meshing parameters, and change "Mesh angle" to be 20 degrees, and uncheck "Add detail to inflections".

That will make the meshing be coarser which will look slightly more jagged in the viewport but there will be many many fewer polygons generated which should help out quite a bit.

I'm going to try to do some work in version 2 to manage this a little more automatically and try to avoid making such high density meshes on things like really small fillets.

But currently you have to alter that setting manually.


> - Some deformation tools would be useful.

Yes, definitely! Unfortunately NURBS solids that are made up of many pieces that touch at trimmed edges rather than natural surface edges do not tend to lend themselves very easily to being deformed.

It's probably going to be a while before deformations like bending or twisting objects will be in MoI. Currently the best way to do this is to use Rhino in combination with MoI - in Rhino version 4.0 there are several new deformation tools added and you can use Copy and Paste between MoI and Rhino to move objects back and forth between them.

- Michael
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 From:  Artaud (PIETRO)
2285.5 In reply to 2285.4 
Hi Michael,

Thank for your answer. I played a little with mesh angles, and yes, it works. Also, I found a script that allows to quickly change the mesh density, that definitely solve the problem of 3D navigation on detailed models.

Regarding rail revolve, I encountered the problem working on a violin.
The first picture is an example of a rectangle revolving on a spiral in MoI, while the second is the same operation made in Rhino.


About deformations: yes, I know how is problematic to deform polysurfaces with a different distribution of control points. I personally do not think that these tools are so useful, since they normally produces very complicated and not so "ideal" surfaces. I was speaking simply about deformation tools for single curves (bend, twist).

BTW, working with MoI is so pleasant, that even if Rhino has many useful commands, and I know well how to use them, after spending few days modeling in MoI, switching back to Rhino interface is hard!
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 From:  Michael Gibson
2285.6 In reply to 2285.5 
Hi Artaud,

> I played a little with mesh angles, and yes, it works.

Great! Hopefully this should get handled better more automatically a bit later on in v2.


> Regarding rail revolve, I encountered the problem working on
> a violin.
> The first picture is an example of a rectangle revolving on a spiral
> in MoI, while the second is the same operation made in Rhino.

I see, that is an interesting way to think of Rail Revolve for that!

Normally the rail revolve type function is more intended to produce something more similar to a simple revolve but kind of stretching it out to match the path curve.

Here are some examples:








The kind of thing you are showing where the profile kind of drags out along a path is normally something that is more the job of the Sweep command rather than Rail revolve.

You should be able to get what you need there in MoI currently by using the Sweep command, but you have to orient it along the z axis direction and use the "Twist:Flat" option, like this:



It is slightly different though, one side effect of the rail revolve is that the profile shrinks in size as it approaches the revolve axis, that is due to the way that Rail Revolve generates its result by applying a kind of scale factor to the shape.


I'll take a look and see if rail revolve can be tuned up in moi v2 to do the same as Rhino though.


> I was speaking simply about deformation tools for single curves (bend, twist).

I see - that is definitely easier than for polysurfaces, but it still might take a while before I'm able to get to this area even for curves. For a while you'll need to move things into Rhino for doing these deformation tasks.


I'm glad that you're enjoying using MoI!

Have you had a chance to try version 2.0 yet? There is quite a lot of new stuff there as well... Some notes here:
http://kyticka.webzdarma.cz/3d/moi/doc/V2releasenotes.html
and for the most recent release here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2170.1


- Michael
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 From:  Brian (BWTR)
2285.7 In reply to 2285.6 
Probably way off beam---does this "in principle" look anything like what is wanted to be obtained in MoI?

Brian

PS/edit
But then I had no need to go scale array either--did I!

EDITED: 2 Jan 2009 by BWTR

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 From:  Artaud (PIETRO)
2285.8 In reply to 2285.6 
Hi Michael,

Yes, in many cases it is possible to obtain the same result of a Rail Revolve operation using the Sweep command. But I think there are some exceptions.

The following example uses a 3D path, and the results produced by MoI and Rhino are different:





Rotating the curve 1 by 90° (2), then scaling it by 1 direction twice (3-4), you get the curve for a sweep.



Unfortunately, the surfaces have some artifacts, but in principle this works.



Anyway, as people often says, "Rome has not been done in a day....". And I think that MoI, as a joung product, is much more than expected!

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 From:  Michael Gibson
2285.9 In reply to 2285.8 
Hi Artaud, yeah the sweep alternative is more for things that follow a longer path instead of being like a dome, more like the scroll shape that you were asking about originally.

MoI's sweep will not work for a dome-like shape currently but I do want to add a kind of pivoting sweep mechanism in later on.


Can you please post the .3dm files of the curves and the results from Rhino so I can use them for testing?

Thanks,
- Michael
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 From:  Artaud (PIETRO)
2285.10 In reply to 2285.9 
Hi Michael,

... I just abandoned the file, without saving it. But it is fast to recreate. You will find it attached.

Notice that the curves (the ellipse and the curve) have been done in Moi then pasted in Rhino.
Then I used RailRevolve command, with ScaleHeight option = On.

BTW, I just published a small article on modeling the Fender guitar on my website. Below is the link:

http://www.robotale.net/joomla/component/content/article/130-test-drive-moi-hendrix-reflections.html

Sorry, the article is in Italian. But maybe someone can use the pictures.

Actually I am playing modeling a violin. It is an interesting challenge... and I have a lot of fun modeling with MoI.

BTW, did you publish Italian U.I.? I used Italian screen dumps for the article, and it would be better that people that will download the software find consistency between images and the version.
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