aligning to tangent points

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 From:  mickelsen
3113.1 
When aligning objects, is it possible to align them to their mutual tangent points, that is, to where they are touching? I can certainly align them to where they look like they are touching, but MoI doesn't know they are supposed to be touching. Is there a way to do it so that MoI knows that they are touching?

Thanks,
Mark
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 From:  Frenchy Pilou (PILOU)
3113.2 In reply to 3113.1 
"Snap On" and Helpers lines are not sufficient?
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 From:  Paolo (PAOLOLOBBIA)
3113.3 In reply to 3113.1 
Hi mickelsen,

In the example i found the tangent point of the cylinder,
using a line and ,Perp/Perp ObjectSnap.
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 From:  Michael Gibson
3113.4 In reply to 3113.1 
Hi Mark,

> Is there a way to do it so that MoI knows that they are touching?

Yup - that's what the Object Snap function is for.

Make sure you have it enabled, there is a button for it in the bottom toolbar here:



I would suggest generally having both "Straight Snap" and "Object Snap" enabled while you are drawing for most cases, so that you get all the helper functions kicking in to help you get accurate results.

When "Object Snap" is turned on, you can just drag one curve starting nearby its end, and it will lock your source point on to it, and then when you move nearby the end of another curve, it will snap exactly on to that other curve's endpoint as well. You will see little "End" marker tags show up to indicate that you are getting an accurate snap point, like this:



If you don't see those "End" tags, then check to see if you have disabled any individual snap types, which is on the menu that pops up from the object snap button (for an illustration of that see here: http://moi3d.com/forum/index.php?webtag=MOI&msg=3100.2 )


You can also use the Transform / Move command if you find that easier than dragging, it lets you specifically click 2 points, a base point and then a target point and will move the object to shift exactly between those 2 picked points.


You definitely should try to get an accurate placement of objects to make them actually touching using the object snap function when pickign points, instead of just "eyeballing" things.


- Michael

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 From:  Michael Gibson
3113.5 In reply to 3113.1 
Hi Mark, also check out the introductory section of the documentation here:
http://moi3d.com/1.0/docs/moi_introduction.htm#drawing

for some more info on the different snap controls and stuff like that.

- Michael
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 From:  mickelsen
3113.6 In reply to 3113.5 
Micheal,
I'm including the drawing that I'm trying to work with, with a lot of stuff hidden to simplify it. I know that several people think that I don't know the first thing about this, but I always have all three snaps enabled while drawing and use the snapping as much as I can. I don't understand the little corner tags quite as well but I'm learning.

In this drawing there are two spheres and a cylinder. If you look at it in the "front" window, what I want to do is move the cylinder down and have it touch both spheres. In the real world, I want the little rod to rest on the balls and make electrical contact with both.

Although I've got just about every kind of snap in the world enabled, I can't seem to get any type of snapping interaction going between the balls and the rod. I'm sure that this is something simple and I am relatively new to MoI. And although MoI is similar to Rhino, it's not identical and that takes me down the wrong path sometimes. Your help is always patient and considerate and never sarcastic, and I appreciate that very much. I'm hoping for that again.

Regard,
Mark
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 From:  Michael Gibson
3113.7 In reply to 3113.6 
Hi Mark, so I think the problem you have there is that snapping happens mostly on curves and edges - there is no curve or edge going around the perimeter of the sphere here:




So you probably want to draw some circles in there (or use the new Construct > Curve > Silhouette command) so that you have a snappable curve there.

You mentioned Rhino - but in Rhino it works exactly the same way, for the most part in Rhino as well snaps target edges and curves and not just in the middle of some surface... You will need to use the same steps for this in either Rhino or MoI as far as I remember anyway.


So what I would do would be to draw in 2 circles like this:



You'll probably also want to switch to the Top view and drag them so that they are centered instead of at one side of the sphere, like this:



Now with those circle curves in place you will be able to snap on to those areas.


Then to get your cylinder aligned, probably your best bet would be to use Draw curve > Circles > Tangent, and enter your cylinder's radius (looks like 0.0625) as the circle's radius, that will work like this:



That circle's center point is then the place you want to move your cylinder to.


Many other kinds of solids may have edges already in strategic places, but a sphere does not - it's only got a single "seam edge" on it and that was not in the area that you wanted to snap on to in this case. When that happens you just need to create some helper circles that you can work off of.

Maybe in the future I will be able to make something like an implicit silhouette on solids that you can snap on to, but that is potentially a slow process to calculate that kind of silhouette on every single kind of surface object so that's why it does not attempt to do it currently.

- Michael

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 From:  Michael Gibson
3113.8 In reply to 3113.6 
Hi Mark, also just another general tip for situations like this - it would probably be better to arrange circles for those things more from the start, then draw in spheres and cylinders snapping on to the circles.

- Michael
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 From:  Michael Gibson
3113.9 In reply to 3113.7 
Also you may want to draw in a new cylinder piece, it looks like the current one you got is maybe a slice out of a longer piece or something? Anyway, it's edge is no longer an exact circle so it is not as easy to get a "cen" snap on it.

If you move the duplicate the edge and turn on control points you can see there are a whole bunch of points in it unlike a regular circle:



So you may want to draw in a new cylinder, or do an extrude of a circle to get a snappable center point on that edge.

- Michael

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 From:  Michael Gibson
3113.10 In reply to 3113.6 
Hi Mark, one other note - it definitely helps a lot when you post a specific model along with your question... It's just too hard to figure out what you might be running into with only a text description.

Like your original question here I could only answer in kind of a general way.

Knowing that you were working with spheres and not just something like line curves, makes a big difference.

- Michael
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 From:  mickelsen
3113.11 In reply to 3113.10 
Actually, Michael, that's exactly what I did to create them in the first place. I drew 3 circles touching in just the way I wanted and then turned them into the spheres and cylinder. Then I realized that the spheres needed to be larger. At that point I should have just started over from scratch but instead I decided to "fix" them. This led me to the situation where I realized that I didn't understand why things didn't work, hence this whole mess.

As for Rhino vs. MoI; they are similar and Rhino is so much superior to systems like AutoCAD that there is no comparison. But MoI is just so much nicer to use than Rhino that...well, I just love it. Even though one might say "If you've got Rhino, how can you justify getting MoI?" Again, ease of use and perception make all the difference.

Again, thanks for being patient. I don't know how you can answer all these questions and still work on the software. Oh yeah, no sleep...
Regards,
Mark
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 From:  Michael Gibson
3113.12 In reply to 3113.11 
Hi Mark, no problem!
quote:
As for Rhino vs. MoI; they are similar and Rhino is so much superior to systems like AutoCAD that there is no comparison. But MoI is just so much nicer to use than Rhino that...well, I just love it. Even though one might say "If you've got Rhino, how can you justify getting MoI?" Again, ease of use and perception make all the difference.

Well, Rhino was my 2nd generation CAD program that I designed.

MoI is my 3rd generation CAD program.

So of course I like to think I have learned over time! :) With the experience of being able to look back, there were a lot of design flaws that I had inadvertently stuck in Rhino which I've been able to correct with MoI.

That's sort of why you get that nicer feeling working with MoI, I was able to "start over from scratch" and fix all kinds of underlying issues.

I originally designed Rhino to run on a Pentium 90 (that's 90 Megahertz!) system with only a wireframe working display. There are still a lot of holdovers in it from that time.

- Michael
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 From:  Frenchy Pilou (PILOU)
3113.13 In reply to 3113.12 
What was the first generation CAD? ;)
And the 4 th CAD will...? :)
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 From:  Michael Gibson
3113.14 In reply to 3113.13 
Hi Pilou,

> What was the first generation CAD? ;)

First generation was a simple mesh based modeling program called Sculptura.


> And the 4 nd will...? :)

Not sure if I would ever have enough energy to start all over again... ;)

- Michael
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 From:  Frenchy Pilou (PILOU)
3113.15 In reply to 3113.14 
THX for these precisions!
---
Pilou
Is beautiful that please without concept!
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 From:  Marc (TELLIER)
3113.16 In reply to 3113.14 
> Not sure if I would ever have enough energy to start all over again... ;)

Lack of energy does not appears to trouble you at all!!

Marc
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 From:  Nick (BODINI)
3113.17 In reply to 3113.14 
> Not sure if I would ever have enough energy to start all over again...

Phfft, thats just 'newborn baby in the house' influenced talk. I happen to be in the same boat and know just how you feel! ;-)
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 From:  Michael Gibson
3113.18 In reply to 3113.17 
Congratulations Nick!

- Michael
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