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Old 15th December 2008, 02:02 PM   #1
Chuck Bodeen
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Default Subdividing and Smoothing

I'm trying to make the fuselage of a hig wing airplane. When I commit subdivisions the model gets wrinkled. The manual says it is supposed to be smoothed.

Subsequent subdivisions result in smaller wrinkles, but there is no smoothing.

What am I doing wrong?
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Old 15th December 2008, 05:48 PM   #2
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Default Re: Subdividing and Smoothing

It's probably something with your topology; I'm guessing that front face is all one poly. How you layout your surfaces and the direction they flow can radically affect how they are smoothed when subdivision is applied.

The easiest rule of thumb to make subdivisions work well is to stick to quads (four-sided polys) for all of your surfaces. It's not a requirement--other shapes can be smoothed with planning--but if you stick to quads you can be pretty brain-dead about your layout and it will still work. Remember, the way subdivision surfaces work is that the surface is split in half on each axis and averaged. Since a quad is already four-sided and will therefore split evenly, it's very hard to go wrong.

If I were going to lay out the topology for your shape, I'd do it something like this:
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Old 15th December 2008, 06:50 PM   #3
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Default Re: Subdividing and Smoothing

Thanks, Lisa.

That means I should start with a cube rather than a cylinder.
I'll try that.

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Old 15th December 2008, 07:34 PM   #4
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Default Re: Subdividing and Smoothing

OK. I now have quads and smoothing - but it is difficult to turn a cube into what is basically a cylindrical or spherical object.

Any suggestions, Lisa? -- or anybody?
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Old 15th December 2008, 11:02 PM   #5
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Default Re: Subdividing and Smoothing

One trick for handling that is to start with a cube, and then use Vertex > Smooth Shape to round the cube off until you have something roughly sphere-shaped to start.

A better way, however, is to use a cube or cylinder to build a single slice of the shape, then extrude in either direction to get the rest of the shape. If you keep your cube very low poly (maybe three or four slices, max) then it will become very smooth\round when you turn subdivisions on, especially if you crank up the subdivision level all the way.

For something like your airplane fuselage, I'd start at the thickest part and build a ring representing just that slice. Once you're happy with it, grab the surfaces and extude forward and to the rear to build each additional slice.

Here's a quick video showing what I mean:
http://www.independentdeveloper.com/files/plane.wmv
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Old 16th December 2008, 12:17 PM   #6
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Default Re: Subdividing and Smoothing

Thanks, Lisa.
The movie really helped!
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Old 22nd December 2008, 04:41 PM   #7
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Default Re: Subdividing and Smoothing

Hi Lisa. I'm back with a much nicer result.
I started with a 2x2x2 cube and smoothed it twice (so far) and then moved vertices to make the cross-sections better. It's still sharp on top because that's where the wings will attach.

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Old 22nd December 2008, 05:29 PM   #8
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Default Re: Subdividing and Smoothing

Hello again!
Now I'm working on the tail boom.
I have made it by copying the aft cross-section of the body and then scaling and smoothing the section at different points.
Can you give me a hint as to how to avoid the missing surfaces and obvious places where I located the cross-sections?

thanks

chuck
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Old 23rd December 2008, 06:40 PM   #9
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Default Re: Subdividing and Smoothing

Can you post a wireframe?

It's hard to tell from the picture, but I think you've got internal faces in your shape--that sometimes happens when you extrude depending on what checkboxes you've got clicked. If you go inside the shape and delete all the surfaces that can't be seen from the outside, the whole thing should become smooth.
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Old 23rd December 2008, 07:19 PM   #10
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Default Re: Subdividing and Smoothing

I have never made a wire frame in AC3D.
I guess now is the time to learn how.

thanks

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