Circle Tangent on a sphere ?
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 From:  bemfarmer
5435.13 
So I've learned that the "On Surface" snap just works in the 3D screen. (?)

I was thinking the center of the circle would be submerged, inside the sphere, and the circle would be on the surface.
(Which construct-curve-project already does.)
A script, if possible, would be able to find that center point. Do not know if it is worth the effort though.
I see that UI PropertiesPanel has a read-only radius...
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 From:  Frenchy Pilou (PILOU)
5435.14 In reply to 5435.12 
@ Michael
<<To do that start the construction line's first point on the sphere...
I don't succeded your last tip, i must miss something !

but I have found another one! ;) Maybe the more easy for the moment :)

I draw my circle on the top of the sphere in view Top

So in view Front I can easily move the Edit Frame circle vertically to the intersection of the "curve's generator" of the sphere!

So I have my tangent circle!

So now with the Orient / Copy I can draw anywhere my circle tangent on the sphere in one click! :) (+ a right click ;)

@Bemfarmer
Courage!

EDITED: 29 Sep 2012 by PILOU

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 From:  Michael Gibson
5435.15 In reply to 5435.14 
Hi Pilou, see here for a demo of doing a construction line along surface normal:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4720.3

- Michael
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 From:  Michael Gibson
5435.16 In reply to 5435.13 
Hi Brian,

> So I've learned that the "On Surface" snap just works in the 3D screen. (?)

Yup, that's correct - in a 2D view it's pretty hard to see whether the point you placed is on a surface or whether it's on the construction plane so some of these kinds of snaps only apply to picks in the 3D view where you can more easily spin around and see the objects that you are drawing on.


> I was thinking the center of the circle would be submerged, inside the sphere, and
> the circle would be on the surface.

If you wanted to do it that way possibly drawing a plane and then using Construct > Curve > Isect to intersect the plane with the sphere would work.

- Michael
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 From:  Frenchy Pilou (PILOU)
5435.17 In reply to 5435.15 
<< a demo of doing a construction line along surface normal:
Yes this gives the helper line on somewhere must be the center's circle inside the sphere
but not the deepth... ;)
Not yet found for example the use of the Orient only for place the circle on this line...and more helper lines for find the good point ...I must explore more :)

EDITED: 29 Sep 2012 by PILOU

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 From:  Michael Gibson
5435.18 In reply to 5435.17 
Hi Pilou,

> Yes this gives the helper line on somewhere must be the center's circle inside the sphere
> but not the deepth... ;)

Well you could use it for example to help draw a cylinder that had a central axis perpendicular to the surface of the sphere but partially submerged inside of it rather than sitting exactly on the tangent plane. Then with the cylinder intersecting the sphere you can intersect them.


> Not yet found for example the use of the Orient only for place the circle on this line..

It will be difficult to find the exact location to position the circle doing it that way - I'd recommend instead using a projection method so that you don't need to worry about the positioning in a manual way like that.

- Michael
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 From:  Frenchy Pilou (PILOU)
5435.19 In reply to 5435.18 
<< Well you could use it for example to help draw a cylinder that had a central axis perpendicular to the surface of the sphere but partially submerged inside of it rather than sitting exactly on the tangent plane. Then with the cylinder intersecting the sphere you can intersect them.

it's that a sort of this I made some post above ;)
<< I can also draw a cylinder from the center of the sphere passing by the point I want then Curve / Intersect and killl the cylinder ! ;)

I don't deseperate to find something easy with the helper lines but for the moment
my above method of the move the Edit frame in Front view + Orient copy everywhere is very satifying and seems the more easy to do (for me) :)

EDITED: 29 Sep 2012 by PILOU

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 From:  bemfarmer
5435.20 
So to generalize, how would it be possible to copy a clothing button, and place it tangent to a surface, such as a sphere, or catenary of revolution, with the "center" at an on-surface point of the surface?

Using the ArrayGem script with a tiny line segment, instead of a point object does such a copy.

Is it possible to modify the ArrayGem factory, to use a PointObject, instead of a Curve?
Changing objectpicker.allowCurves() to objectpicker.allowPointObjects() in the script, does not work, so the change would have to be in the ArrayGem factory, (I think).



EDITED: 23 Aug 2014 by BEMFARMER

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 From:  Michael Gibson
5435.21 In reply to 5435.20 
Hi Brian, it should probably not be difficult to modify the ArrayGem factory to work like that, I'll take a look at that tomorrow.

- Michael
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 From:  bemfarmer
5435.22 In reply to 5435.21 
Hi Michael, I've just been messing around, practicing MoI. Ideas may or may not be useful or practical.
Seems like the orient command does the trick well.
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 From:  bemfarmer
5435.23 
.

EDITED: 30 Sep 2012 by BEMFARMER

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 From:  Frenchy Pilou (PILOU)
5435.24 
Ok I have successful with use only the Orient and helper lines ! ;)

Same trick than my previous try for inspiration :)

Circle given is drawn somewhere on the ground: click on it for have the radius
Call the Orient
In view Front draw a vertical helper line from the top of the sphere
Move it of the radius given of circle
Redraw one vertical line at the Top of the sphere
Draw an horizontal helper line from the intersection of the previous vertical helper line of the radius and the generator curve of the sphere

Et voilĂ  ! :)
I can draw the Orient Circle at the good deepth!
After that just now take the top of the sphere as Base Origin!
And copy it anywhere!



EDITED: 30 Sep 2012 by PILOU

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 From:  bemfarmer
5435.25 In reply to 5435.21 
Michael, did you look at the possibility of using the ArrayGem factory with Point Objects, rather than
lines or curves? (While preserving the On Surface normal orientation?)

Thank you,

Brian
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 From:  Michael Gibson
5435.26 In reply to 5435.25 
Hi Brian, yup using points with ArrayGem is set up for the next v3 beta - you won't have to do anything custom you will just be able to select point objects in addition to curves for the target objects in the regular command.

- Michael
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 From:  bemfarmer
5435.27 In reply to 5435.26 
Should be very useful! :-)
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