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Can't create smooth 3D solid
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December 07, 2017, 05:51:42 PM
(This is not an issue with faceted surfaces.)

I'm trying to create a 3D infinity symbol.  I used a 3D spline and tried both a sweep and a rail sweep with a 2D ellipse, which works just fine (...for the most part.  See the last paragraph below).  But you can't use multiple 2D objects to define the profile (like you can with Lofting).  If I could select a number of ellipses of different sizes along the 3D spline, this would work, but you can't.

I want the symbol to have varying thicknesses; thicker in the front part and thinner in the back, to give it more perceived depth.  The only way I could figure out how to do that was to create a series of ellipses of varying size along a path and use the Lofting command.  One problem was I don't think you can close a series of profiles with Lofting to finish at the first 2D profile object (like you can close a polyline), so I had to create it in two sections (it would be nice to be able to close that sort of extrusion).  I got the two pieces to generate just fine (and they seem to match up), however, using this command results in a rather lumpy infinity symbol (see attached picture).

I can't think of another method that will accomplish what I'm after.  Any ideas on how to do this?

Another problem I noticed was after laying in the points of my 3D spline (by Fit Points), TurboCAD seems to want to relocate my points to other locations.  Looking at the attached picture, you can see the series of arcs and how the spline decided to move its control points away from where I placed them (at the centers of the arcs).

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December 07, 2017, 05:54:51 PM
#1
Here's a better view of the 3D spline with the fit points moved from where I placed them.  (They're supposed to be at the centers of the ellipses placed along the path.)

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December 07, 2017, 05:58:33 PM
#2
...and here's a perspective of everything from a different angle so you can see it all.

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* December 07, 2017, 06:20:26 PM
#3
Perhaps you could impart actual depth, by Sweeping a circular or elliptical profile along a 3D Spline which itself has the actual depth. View the finished object with Perspective enabled.

Henry H

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* December 07, 2017, 06:47:11 PM
#4
...Something like this...

Henry H

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December 07, 2017, 07:40:48 PM
#5
That LOOKS fantastic, but not what I'm after.  I'm not trying to create a 2D picture with perspective of the model.  I actually need a 3D solid that varies in size along the path of the symbol.  I actually want to look at the back side and see the skinny section in front and the fat in back as well as look at it from the front and see the fat in front and the skinny in back.

I need something that looks like your picture but has overall physical dimensions something like 2" x 1" x 0.25".

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* December 08, 2017, 09:49:52 AM
#6
Here's a better view of the 3D spline with the fit points moved from where I placed them.  (They're supposed to be at the centers of the ellipses placed along the path.)

Did you try "graphic on path"
> I used a 3d control point spline as the path
> adjust the profiles.

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December 08, 2017, 10:16:00 PM
#7
Dean, I'm not sure what you mean.  Graphic on Path just gives me a number of 2D ellipses along the spline, not a solid.

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* December 09, 2017, 08:33:51 AM
#8
Yet another way (see attachment)…

1.   Draw two 2D Polyline paths, back to back, each consisting of a circular arc and a short line segment. Draw a circular profile, rotate and move it so its axis is tangent to the arcs of the two Polylines.

2.   Sweep the profile along each of the paths and adjust the Draft of the sweeps.

3.   Move the Reference Point of each sweep to the center of the circular profile, then rotate each sweep about the axis of that profile (rotate one sweep upward and the other downward.

4.   Make a copy of each sweep; rotate the copies 180° about the World Y axis and then 180° about the X axis. Relocate the copies as shown.

5.   Explode the sweeps into ACIS Solids and use Face to Face Loft to close the gaps. 3D-Add the components.

Henry H

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* December 09, 2017, 05:33:32 PM
#9
I did it as Dean suggested.

> First created a 3D Spline that was half of the Infinity symbol (the Coral colored spline, in the pic below)
> Then created a circle on one endpoint of that spline.  Used Graphic on Path, Nearest on Graphic snapping in Plan View, to-- bye eyeballing it*-- evenly distribute the circles on that spline.  (The green circles, in the pic)  (I liked the way the circles stayed "normal" to the spline, using the Graphic on Path command)
> Individually selected and resized each of the circles, using some math to determine what size each one should be so that when I went to Loft, the eventual Loft would pretty much uniformly taper down.
> Copied the Spline and Circles to the corresponding other side (the half that is on the left-- blue Spline, black Circles)
> Used the Loft Tool to loft, selecting all the Circles for the loft, starting and ending  with the one at the top-left in the pic (where there is a bit of a sharp point)

Thanks for the exercise.

____________
* "...Nearest on Graphic snapping in Plan View, to-- bye eyeballing it...":  I should have used a Divide Snap, first setting the Divide Snap to about 10--  I think.
« Last Edit: December 09, 2017, 05:44:05 PM by Alvin Gregorio »

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Alvin Gregorio
(mostly Residential Architectural 2D; no formal CAD Training; intermittent TurboCAD user since yr. 2000 [ver6.5])
---TurboCAD: V20.2PP(57.0)[as of 3/12/15]; V19DL(54.2); V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


December 09, 2017, 09:24:37 PM
#10
Finally got it!

To me the Lofting command doesn't draw a very smooth solid like I think it should, otherwise I wouldn't have had all these problems.  Seems to somewhat abruptly curve at the ends, unlike splines do which remain smooth through out.

I had never used the Graphic on Path command before (or any of the 3D Assemble commands).  You tend to get used to the set you commonly use, so this was a good exercise to force me to "try somehthing new."  Sometimes I think I need to just go explore once in awhile but never get around to it.

I do like how the Graphic on Path command places the 2D profiles perpendicular to the spline with ease.

Alvin - Thanks for the explanation.  I thought Dean was trying to say a solid could be drawn by his method (which it can't) - you still need to use Lofting.  However, I still see some lumpiness in your example. 

Since you used 20 total profiles, I ended up using 80 divisions.  On the straighter sections, I didn't use quite so many divisions as they weren't that necessary.  Scaling all those profiles took quite awhile, however.

I also decided to stay with a 3D Spline as I decided to shift it a bit to give it more of an italic look.  Now, there's nothing isometric about it at all, which made it harder to draw, but I think makes it that much more beautiful, in my opinion.  But it took an awful lot of work!

Thank you all for your suggestions!

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* December 10, 2017, 03:29:28 AM
#11
Might be easier to bend a straight one.....

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* December 10, 2017, 06:50:20 AM
#12
Might be easier to bend a straight one.....

That's what I was thinking.  Using the Bend to Path Tool (released V-2016?) seems like it would be especially useful.
Now, when they come out with a Bend to Path capability of the path being a 3D Polyline or Spline, then they really have something.
-Alvin

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Alvin Gregorio
(mostly Residential Architectural 2D; no formal CAD Training; intermittent TurboCAD user since yr. 2000 [ver6.5])
---TurboCAD: V20.2PP(57.0)[as of 3/12/15]; V19DL(54.2); V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


* December 10, 2017, 09:43:40 AM
#13
Might be easier to bend a straight one.....

That's what I was thinking.  Using the Bend to Path Tool (released V-2016?) seems like it would be especially useful.
Now, when they come out with a Bend to Path capability of the path being a 3D Polyline or Spline, then they really have something.
-Alvin

V17 can bend along a 3D Spline path.

Henry H

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* December 10, 2017, 10:50:42 AM
#14
...
V17 can bend along a 3D Spline path.

Henry H

Then this infinity symbol otta be a slam-dunk in V17, using the Bend to Path tool along a 3D Spline.  Right?
Is that really V17?, or V2017?

-Alvin

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Alvin Gregorio
(mostly Residential Architectural 2D; no formal CAD Training; intermittent TurboCAD user since yr. 2000 [ver6.5])
---TurboCAD: V20.2PP(57.0)[as of 3/12/15]; V19DL(54.2); V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)


* December 10, 2017, 12:33:15 PM
#15
...
V17 can bend along a 3D Spline path.

Henry H

Then this infinity symbol otta be a slam-dunk in V17, using the Bend to Path tool along a 3D Spline.  Right?
Is that really V17?, or V2017?

-Alvin

2017. Sorry about that.

Henry H

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