Beginner:Forming a solid from projected curve  1-20  21-24

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 From:  Stever_uk (STEVER)
4657.1 
Hi,

I have formed these two surfaces from using curves/project with a sphere.
I now wish to make a solid out of these surfaces.

Now I know these are not solids, so I have tried using a combination of join, blend and planar but still no joy

Obviously doing something silly, can anyone point me in the right direction
cheers

EDITED: 31 Oct 2011 by STEVER

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 From:  FelixPQ (FELIX)
4657.2 In reply to 4657.1 
Hi,

I've made 2 versions of what I think you want but maybe I got it wrong.

For the blue version, I use a line to join the circle edge with the other surface and then used sweep to create a surface on one side. I did the same on the other side and join all surfaces together.

For the red version, I basically started from scratch to create a more squarish object with a hole in the middle. I then used the new command flow in projection mode the get the red object.

Personnaly, I prefer the red version but it's a question of taste I suppose. Hope this help, I'm a newbie myself and wanted to try it.

Regards,
Felix
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 From:  Stever_uk (STEVER)
4657.3 In reply to 4657.2 
thanks Felix,

Exactly what was after. However I'm confused and not understanding something here.

If get a poly curve and stick a circle inside, then a extrude, I get a cap. great, no problem.

However if I do the same thing with the two curves I created as a result of the curve/isect using a sphere, I don't get a cap if I extrude

??
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 From:  FelixPQ (FELIX)
4657.4 In reply to 4657.3 
Stever,

The cap option or planer cmd. wont work if the surface is not planer, in this case it's obvious that it's not. It's why I started from scratch for mthe red version.

As I said earlier, I'm a newbie myself and it's difficult to explain but if you could tell which approach you're trying now, red or blue? I could try to give you better explanation.

Felix
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 From:  Stever_uk (STEVER)
4657.5 In reply to 4657.4 
Thanks for your help Felix :)

Getting that shape is not the problem just the reason why and as you explained it needs to be planar

I would of thought it would be common to generate objects from curves as a result of a projection.
Thanks again

EDITED: 31 Oct 2011 by STEVER

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 From:  Stever_uk (STEVER)
4657.6 In reply to 4657.5 
for instance

I have extruded this shape from a projection of the main body (sphere). I have successfully fillet it but how would one seal this shape, (ie give it a cap)?

Steve

EDITED: 31 Oct 2011 by STEVER

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 From:  BurrMan
4657.7 In reply to 4657.6 
Hi Steve,

You should really review cutting up solids and keeping them that way first.

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 From:  Stever_uk (STEVER)
4657.8 In reply to 4657.7 
thanks for the video, much appreciated BurrMan

"You should review cutting up solids"

is there specific documentation/topic on this?

I'm currently working through the MoI command reference and posts
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 From:  SteveMacc (STEVEH)
4657.9 
Easiest way is to create your sphere. Then draw your hex shape. Use trim to cut the sphere with the hex and discard the bits you don't need. You will then have a surface that would be one of your caps. Just extrude this surface. then boolean a cylinder out of the middle.

You can extrude a non planar surface, because MoI caps it with the original surface.
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 From:  Stever_uk (STEVER)
4657.10 In reply to 4657.9 
blimey,

thanks Steve
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 From:  Michael Gibson
4657.11 In reply to 4657.1 
Hi Steve, so the big step that you're kind of missing here is that when you project a curve onto a surface, you often don't want to get rid of the surface and try to recreate it from scratch, instead you want to actually make use of the surface itself too, like for instance by trimming the surface by that curve.

Trying to recreate the surface that goes through a non-planar projected curve is going to be really difficult - but you don't need to recreate it, because you've already got it there since it was what you projected on to in the first place. You just need to cut it using the Trim command.

But also another thing is that several commands like both booleans and trim already have curve projection built into them so you don't need to do them as a separate manual step like it looks like you've done here.

It looks like the final result that you want is an extrusion with rounded ends.

A good way to create that is actually by a totally different process than projecting curves and then trying to create surfaces to fill them in, you can instead build an extrusion and then cut the extrusion to produce the rounded ends.

So in your case here, you'd start with 2 planar curves like this:



Extrude those out to make your base shape:



Now position some spheres to use for cutting it up:




Select all 3 objects, and then use the Construct > Boolean > Merge command, that will slice up all the objects and leave all the results behind, then you just delete the parts that you don't want to keep. After you delete the pieces of the sphere you'll see your extrusion was sliced up like this:



So then delete the outer pieces and only keep this inside one which has the shape you want:




Usually this kind of process of building an extended solid base shape and then cutting it up is the best way to approach things rather than trying to build individual projected curves and then trying to fill those in.


You want to kind of take a look at your object and try to think if it has some kind of central underlying element to it which is then cut off at a certain spot. In your case it's exactly that - you want to have a base shape that is an extrusion but that then has cut off rounded ends. So usually with NURBS modeling you want to actually build in that exact method, build the extrusion and then cut it as shown above.

- Michael

EDITED: 31 Oct 2011 by MICHAEL GIBSON


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 From:  Michael Gibson
4657.12 In reply to 4657.11 
So like you guys are mentioning above you can also build this shape by building just a starting surface and then extruding it - if you extrude a surface you will always get caps on it since it can be capped just by copying the potentially non-planar surface to the other side.

But I would encourage you to think more along the lines of slicing a base solid like I showed above, because it's a lot more general purpose and you will generally use that same process to take other kinds of cuts out of the object as well like slicing it by side profiles.

If you did want to do it by extruding a surface you don't need to use curve projection as a separate step because Trim already has projection built into it, so just trim the sphere directly with your 2D profiles, then extrude the trimmed sphere surface piece.

- Michael
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 From:  Michael Gibson
4657.13 In reply to 4657.1 
Hi Stever - also see some of these previous threads for some other discussion about modeling with solids and cutting up extended shapes.

This is basically a key difference between the NURBS modeling process and the polygon modeling process - with NURBS modeling booleans and cutting operations are a primary way of doing things and often times that will mean making an initial simple extended piece and then cutting it up rather than trying to sort of draw a net of 3D curves and then trying to fill them in, which is also possible but better reserved for more special situations.

Anyway, some other discussion on this here:

http://moi3d.com/forum/index.php?webtag=MOI&msg=4640.4
http://moi3d.com/forum/index.php?webtag=MOI&msg=3795.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=4298.4
http://moi3d.com/forum/index.php?webtag=MOI&msg=4163.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=2282.2

Some of those threads may help to give you more of the idea of the different modeling mindset (as compared to polygon modeling) that you generally want to approach things with in MoI.

- Michael
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 From:  Stever_uk (STEVER)
4657.14 In reply to 4657.12 
Hi michael,

Much appreciate the explanation, learning a lot.

Can give me a scenario when you would best use curves/isect

EDITED: 31 Oct 2011 by STEVER

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 From:  Michael Gibson
4657.15 In reply to 4657.14 
Hi Steve, since Trim and booleans actually have curve projection or extrusion built in, you usually would use curve projection only for intermediate construction steps, like for instance see here for an example where curves are projected on to a sphere and then used as the paths for building sweeps:
http://moi3d.com/forum/index.php?webtag=MOI&msg=817.8

Working with individual surfaces where you would trim individual surfaces instead of solids tends to be a somewhat more advanced kind of toolset, it can sometimes be helpful to work at a surface level if you want to kind of disassemble and rework some particular area of an existing solid though. There is an object repair tutorial here that shows that kind of use in a lot more detail:
http://moi3d.com/forum/index.php?webtag=MOI&msg=446.17

But as far as building basic models goes, I would encourage you to focus more on using solids for doing basic shapes since for general stuff it tends to be more convenient and quick to use the solid toolset.

- Michael
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 From:  Michael Gibson
4657.16 In reply to 4657.14 
Hi Steve, also one other note:

> Can give me a scenario when you would best use curves/isect

You still do use curves when working with solids as well, like for example in the solids workflow that I showed above there are still curves involved as the first step in creating the base extrusion shape.

The difference though is that you can make stuff happen working more with 2D curves only rather than trying to work with curves that are warping around all over the place in 3D.

Of course, it also all depends on what kind of work you're doing and what particular kinds of models you're creating - if your models are made up of more stylized swoopy surfaces that don't resemble extrusions or revolutions very much then you'll proably be working more with 3D swoopy curves to construct such stuff.

If your models look more like they incorporate some more 2D profile elements in them like they have the base shape of an extrusion, then those are the kinds of things that tend to happen more quickly and easily by working with 2D curves and solids rather than working with 3D swoopy curves.

This is all just kind of general advice though - which particular tools will work best can depend on what particular kind of shape you're trying to build.

The kinds of shapes that are well suited for using 2D curves though tend to be the ones that you can really get built very quickly using more solids + booleans methods though.

- Michael
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 From:  Stever_uk (STEVER)
4657.17 In reply to 4657.16 
Great stuff, thanks Michael
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 From:  Rich_Art
4657.18 In reply to 4657.17 
Yeah cool solution indeed yhanks for that Michael.
I need to change the way how I think something must/can be modeled. I still think to much in a polygon way. :-)

Peace,
Rich_Art. ;-)

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 From:  Stever_uk (STEVER)
4657.19 In reply to 4657.18 
"...I still think to much in a polygon way. :-)"

I think that's half my problem as well :-)

Steve
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 From:  Rich_Art
4657.20 In reply to 4657.19 
LoL.. Nice to hear I'm not the only die hard polygon modeler. :-)

Peace,
Rich_Art. ;-)

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