Transition from oval to round?

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Transition from oval to round?

Postby willwillwillwill » Mon Feb 13, 2012 12:34 am

This might be an easy question, but I am not sure what to call this step to find a proper tutorial.

I want to transition from the oval on the top plane to the circle on the bottom plane. Is this possible in Sketchup?

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Re: Transition from oval to round?

Postby mitcorb » Mon Feb 13, 2012 3:09 am

Short answer, yes. And it can be done with no extra, or special tools. With a few basic assumptions and only the image you provided, I would suggest first simply to draw line by line from each vertex on the topmost "oval" (not really an ellipse)down to a corresponding vertex on the circle below. You may have to draw diagonals to make the faces fill. Another method is to construct a cylinder, select the top circle right click explode curve select a series of the edges as an arc do a horizontal or axial move and it will stretch in the shape you call an oval. The cylinder retains its faces. See if this helps.
EDIT: see attached.
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Re: Transition from oval to round?

Postby TIG » Mon Feb 13, 2012 12:08 pm

What was originally show isn't an 'oval', it's a 'lozenge' - a rectangle with rounded ends.
This means that the suggested method of scaling a circular top of a cylinder into an 'oval' [ellipse] won't work.

The lozenge has at least two extra segments around its perimeter compared to the simple circle [4 as drawn!], that is assuming that the two semi-circular ends have the same number of segments as half of the full-circle.

You can allow for this by making a circle with say 24 segments and adding arcs as the ends with say 11 segments so the total perimeter segment count is the same.
Then with the two loops arranged vertically above each other 'stitch' the two forms together by drawing from node to node to make triangular faces - you could do just 1/4 then copy those faces to the side scale 1- to hand and snap/relocate, then repeat with the half to complete the perimeter connections...

Another way is to draw the flat faced lozenge with a slightly smaller circular face in its center and then select that circular face and Move it vertically with Alt press to induce auto-fold - then the sides are made for you. At the end to make the top circle the same size as the width of the lozenge select the circle, scale it + Ctrl to be by center and type in a dim [with a units suffix] to match the lozenge's width - e.g. 500mm...
Capture.PNG
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Re: Transition from oval to round?

Postby willwillwillwill » Mon Feb 13, 2012 11:55 pm

I was hoping for a button to press to make it work, but this helps. Thanks.
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Re: Transition from oval to round?

Postby d12dozr » Tue Feb 14, 2012 12:18 am

the Curviloft plugin has a button to do that....search the forum for the download link
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Re: Transition from oval to round?

Postby Wo3Dan » Tue Feb 14, 2012 9:34 am

Here's a simple method:
- draw a circle, correct radius, with an even number of segments
- draw a centerline (preferably one that runs parallel to a drawing axis)
- pull up one half of the circular face to desired height
- move that extruded half circular top face to the side, perpendicular to the centerline's axis (that's way axes constraining makes it so easy)
- repeate "pulling up and shifting to the side"-process for the other half circular face. The shifting however is in opposite direction.
- fill in the two missing 'lozenge' segments, to comple the lozenge.
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Re: Transition from oval to round?

Postby Gaieus » Tue Feb 14, 2012 10:55 am

Maybe another method.
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Re: Transition from oval to round?

Postby Alan Fraser » Tue Feb 14, 2012 11:42 am

Transitioning from a true oval (not a lozenge) to a circle couldn't be easier. Simply draw a circle, extrude it, then scale to top face in one direction while holding down Ctrl.
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Re: Transition from oval to round?

Postby Gaieus » Tue Feb 14, 2012 12:02 pm

Ah yes, Alan, but according to the image in the first post, it's indeed a lozenge... (Otherwise Fredoscale could be used to "scale" it to a lozenge, too)
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Re: Transition from oval to round?

Postby Alan Fraser » Tue Feb 14, 2012 12:13 pm

Yes, I noticed that. I also noticed that it's a negative shape...unlike your's, mine or anybody else's examples. ;)
Not that that would make any difference if you were merely going to stitch the nodes together.
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Re: Transition from oval to round?

Postby Gaieus » Tue Feb 14, 2012 12:25 pm

Well, often simply stitching is the fastest and easiest way actually. ;)
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Re: Transition from oval to round?

Postby Dave R » Tue Feb 14, 2012 2:02 pm

One more way. No plugins needed.

circ toloz.png


Draw a circle. Drag radius out on axis.
Rotate circle so edges are on axis. If you use a default 24-sided circle, rotate the circle 7.5 degrees.
Use Push/Pull to create cylinder.
Select top edge, right click, choose Explode Curve.
Use a left to right selection box to select half of circle*.
Use Move tool to move the selection the required distance.
Repeat for the other side.

It's not really half of the circle. It's half minus the two edges that will be the long edges of the lozenge.
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Re: Transition from oval to round?

Postby Jean Lemire » Thu Feb 16, 2012 5:12 pm

Hi folks.

See this SU file for ideas.
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Re: Transition from oval to round?

Postby derei » Thu Feb 16, 2012 5:28 pm

TIG wrote:What was originally show isn't an 'oval', it's a 'lozenge' - a rectangle with rounded ends.
This means that the suggested method of scaling a circular top of a cylinder into an 'oval' [ellipse] won't work.

The lozenge has at least two extra segments around its perimeter compared to the simple circle [4 as drawn!], that is assuming that the two semi-circular ends have the same number of segments as half of the full-circle.

Sorry for off-topic, as I'm not a native english speaker, I'm always interested in learning.

I always thought that "lozenge" is something else, and Wikipedia says the same http://en.wikipedia.org/wiki/Lozenge

Also, there seems to be a slight difference between oval and ellipse as they show it here http://en.wikipedia.org/wiki/Oval

So, what's the name of this shape formed by two half of circle joined by segments?
Thanks
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Re: Transition from oval to round?

Postby TIG » Thu Feb 16, 2012 5:45 pm

An ellipse is a geometrical figure - a circle is a special case of an ellipse, where both axes are the same length.
An oval is a more general term meaning 'egg-shaped'; so it could refer to an ellipse OR to a non-elliptical egg form.
A lozenge can indeed be a 'diamond-shape' - this comes from 'heraldry' [many rhomboid shapes with two axes of symmetry [that are not 'oblongs'] can be thought of as 'lozenges']... but today most English speakers will hear the word 'lozenge' and think of something that is a rectangular shape with rounded [rather than pointed] ends - like a throat-lozenge candy/sweet made that shape so it is easier to suck/swallow - this kind of 'lozenge' usually has two ends that are are semi-circular, although four rounded corners can also make a 'lozenge-like' shape... See here http://www.google.co.uk/search?q=lozeng ... 40&bih=779
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Re: Transition from oval to round?

Postby derei » Thu Feb 16, 2012 6:04 pm

@ TIG
Thank you very much! I always cherished your help and explanations.
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Re: Transition from oval to round?

Postby mitcorb » Thu Feb 16, 2012 8:13 pm

I am glad that TIG was able to help you.
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Re: Transition from oval to round?

Postby Gaieus » Fri Feb 17, 2012 12:14 pm

This is what our beloved SU (pro) companion, LayOut draws as a lozenge.
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