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# Tangent snaps not reliable?

## Question

Is the Tangent Snap unreliable?

Tangents from opposite sides of a circle should mirror.

Option key reverses sides, but start points are not symmetrically aligned

One workaround is to snap the first one, then use the Mirror tool.

But is the 1st one really tangent?

-B

## Recommended Posts

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1 hour ago, Benson Shaw said:

Is the Tangent Snap unreliable?

Tangents from opposite sides of a circle should mirror.

Interesting. When I tried it the vertical line connecting the two is not vertical at all.....

I've never found tangent snaps in VW very reliable. I tend to draw a known tangent and rotate it around the circle to where I need it. I also wish there was a way for the second click to be the tangent point on the circle (eg. from a point on another object to the tangent point on a circle).

Kevin

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Well picked Benson.

When I did my own test I discovered that both tangents are actually wrong.  The angles between the radius lines and the tangent lines should be 90° and neither of them are that.

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Thanks @Kevin McAllister & @mike m oz for looking and further analysis and commentary.

Yeah, this is not new. I’ve always had trouble with vwx tangents, often use workarounds. This seemed over the top, so I posted here and submitted a bug.

Time to retool this snap.

I too want the tangent snap to apply to both the fist click to lock onto a curve AND to a second click to find tangent on another curve. I say curve rather than arc to expand the functionality into objects with variable radius.

And in 3d, how’s about linear and planar tangents between curved surfaces or planar curves and curved surfaces?

-B

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Tried in V19 and V20,

both Tangents completely OFF.

The upper tangent visibly off.

The lower tangent (by holding ALT key) looks good but provides

2 snapping points !?

The whole Tool usage,

to have to start a Line from the curve intersection point first and then

set your fixed point !?

Feels totally mixed up for me.

Like mixing up the grammar in a sentence.

And the need to temporarily switch tangent snap on and off again.

Why not a permanent tangent option in snaps, that will show just

when you hover over a potential tangent point on a curve ?

For me it looks completely broken.

And thanks @Benson Shaw for finding this.

It is at least very good to know, that you can't rely on this.

BTW,

why does my Circle look like a Polygon, when I zoom in, even

in 2D Top Plan View at all ?

Thought it would look true round and that would be polygonal only

in 3D Views ?

Edited by zoomer
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Tried the tangent a few times and it just works properly with giving 90° angles where it should IF I take care of the hint showing tangent/tangent before clicking. If I don't do this and click before the tangent/tangent hint shows then it might be off as in the above examples.

My impression is that it may technically speaking not be broken but it is quite finicky to make it work, it definitely should work more easily/straightforward with an easy to notice snap to tangent because the current implementation just allows for too much chance of error/failure because the snapping is not showing clear enough if not zoomed in.

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Horsing around some more.  2 more things of note:

1. The tangents seem to work except to a target horizontally aligned with the curve center and in the positive direction.

2. Tangents to target close to the curve cannot differentiate the opt/alt key.

I took my test away from the drawing origin in case that is an issue.  Targets between the axes are not shown, but those seemed to work OK, too.

8 hours ago, zoomer said:

Why not a permanent tangent option in snaps, that will show just

when you hover over a potential tangent point on a curve ?

This could be a good feature, but needs a defeat option, similar to the ` key (temporarily defeats ALL snaps).

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23 minutes ago, Art V said:

IF I take care of the hint showing tangent/tangent before clicking.

I don't ever see a tangent/tangent hint if I'm snapping tangent from a circle/arc to a point on a line or a point in the drawing space.

I think the tangent/tangent hint only shows if snapping a line object tangent from one arc to a second arc?

Drawing an arc or other curve to be tangent between a couple target curves seems out of the snap capability.  Workaround is to use a fillet, but then radius must be chosen in advance.

Edited by Benson Shaw
cosmic
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1 hour ago, Art V said:

Tried the tangent a few times and it just works properly with giving 90° angles where it should

Unfortunately I only tried the the right part with the black lines in @Benson Shaw example so far.

(With the same or worse result)

1 hour ago, Benson Shaw said:

This could be a good feature, but needs a defeat option, similar to the ` key (temporarily defeats ALL snaps).

I meant it in a way similar to a perpendicular snap option :

- start you Line with first point to "rubber band"

- hover cursor over a circle/arc/curve

- move cursor along the curve, click when the Tangent Snap Icon

appears when in snap tolerance, to confirm Tangent Snap.

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10 hours ago, zoomer said:

The whole Tool usage,

to have to start a Line from the curve intersection point first and then

set your fixed point !?

Feels totally mixed up for me.

Like mixing up the grammar in a sentence.

Hmmh,

it looks like it already works that way.

- Start your Line anywhere and hover on Arc later > Tangent Option hint appears and works.

Also the other way round as I used before :

- Hover cursor over arc > On Element Snap > Click = Start Point

- rubber band will move first point along Arc so that it keeps tangent

- click 2nd point of Line

I mean in general, but just as @Benson Shawexperienced,

not when I start a Line at the same Y horizontally as the Y value of my Circle center ....

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1 hour ago, Benson Shaw said:

I don't ever see a tangent/tangent hint if I'm snapping tangent from a circle/arc to a point on a line or a point in the drawing space.

I think the tangent/tangent hint only shows if snapping a line object tangent from one arc to a second arc?

Drawing an arc or other curve to be tangent between a couple target curves seems out of the snap capability.  Workaround is to use a fillet, but then radius must be chosen in advance.

Yes the tangent/tangent shows when drawing a line tangent from one circle to tangent to another circle.

However when I create tangent lines from a circle to another point it also works without issues provided I start at the circle towards the other point regardless of angle to that other point.

I don't know how close your target was to the circle but reasonably close targets did work in this one, the alt key working also.

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9 minutes ago, zoomer said:

not when I start a Line at the same Y horizontally as the Y value of my Circle center ....

Yes, that is where it tends to get a bit tricky depending on the distance to the curve/circle and the radius, the most reliable way to get a tangent line seems to be when you start at the curve/circle/arc to your destination instead of the other way around.

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You can try to set a 8 m Circle on 0,0

and a Line from 0,0 to 30,0

(pretty similar to Bensons example and his black Lines)

No you can try either from Circle to end of Line

or from end of Line to Circle.

Both won't work for me.

Everything else seems to work.

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25 minutes ago, zoomer said:

You can try to set a 8 m Circle on 0,0

and a Line from 0,0 to 30,0

(pretty similar to Bensons example and his black Lines)

No you can try either from Circle to end of Line

or from end of Line to Circle.

Both won't work for me.

Everything else seems to work.

Yes, if the the end of the line horizontally aligns with the centre then the angle will not be 90°, regardless of the horizontal distance to the centre being 30m or smaller or larger.

If the end of the line is just very slightly above that point (e.g. Y=0.001) then the angle will be 90° as shown in the screen capture.

So something is definitely not working properly in that particular situation. it doesn't matter whether the centre of the circle is at origin or not.

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Yes, seems that a snap alignment through the curve center AND parallel to x axis causes the tangent acquisition to disable in preference to the new acquisition anywhere on that horizontal extension line.  But the tangent reacquires as soon as cursor is away from the alignment.

Strangely, any other extension line alignment passing through the curve center does not cause this problem ???

-B

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10 hours ago, Benson Shaw said:

Strangely, any other extension line alignment passing through the curve center does not cause this problem ???

Something I did wonder but didn't get to testing yesterday was this, and then wondered if it only applied to lines aligned horizontally and vertically with the centre.

So I did a quick test and now it gets even a bit stranger, given your video it was to be expected that vertical lines aligned with the centre are not an issue, but horizontally aligned with the centre would be an issue. Apparently not entirely true

It only happens with a target horizontally aligned with the the centre in the positive X direction, not in the negative X direction which is not what I would have expected.

Something really weird and wrong is going on here, why would this happen only with a target aligned horizontally with the centre and only in the positive X direction????? 😲

{Edit: Just filed a support request at the Benelux VSS support for this issue]

Edited by Art V
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In the version I'm currently using (2017), tangents behave properly with respect to being 90d from the corresponding radius line.  The only odd thing is that when snapping to the end point of a horizontal line, the tangency sometimes flips 180, and I have to use the <alt> key to get it to snap to a point on the other side of the circle.  Maybe something was fixed incorrectly between then & now?

By the way, the reason I haven't installed my 2020 version is that I keep hearing about problems with v2020, and no fixes to longstanding problems or deficiencies that make it worth the effort to switch.  I'm pretty sure I'm dropping out of Service Select and upgrades this year.  Any advice to the contrary would be appreciated!

VW v2017 SP5

Win 7 x64

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Pete, Vw 2020 is very stable and things work as they have always done.  I can't think of any reasons to not upgrade.  Try it because you might be pleasantly surprised.

If it doesn't work out for you you can always go back to an earlier version.  I collaborate with another architect who uses an earlier version and haven't had any problems with exporting back to the version he uses.

I'm optimistic about Vw 2021 because the core program is more solid now than previous versions.  I've reported fewer bugs for Vw 2021 than I have for any of the previous versions.  Less time fixing bugs should mean more time working on improving capabilities.

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14 hours ago, mike m oz said:

I can't think of any reasons to not upgrade.

@P Retondo I agree with Mike on this. I could imagine not upgrading to VW 2019 until the later SP's because that one was one of the more buggy releases in years, but so far I have not seen any major issues with VW 2020 that would make me avoid upgrading.

Compared to the 2017 version there are some substantial benefits (if you have use for them of course) that would be worth to upgrade for also because I don't see any real showstoppers in VW2020 (though I am using Landmark the core functionality should work similarly well (or not depending on the issue)).

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On 1/2/2020 at 5:23 PM, Kevin McAllister said:

I've never found tangent snaps in VW very reliable. I tend to draw a known tangent and rotate it around the circle to where I need it. I also wish there was a way for the second click to be the tangent point on the circle (eg. from a point on another object to the tangent point on a circle).

Kevin, do you really think this is acceptable?  Tangency geometry is pretty straightforward, you could construct a bulletproof algorithm in less than an hour.  I just think there is some careless engineering going on.

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20 hours ago, P Retondo said:

Kevin, do you really think this is acceptable?  Tangency geometry is pretty straightforward, you could construct a bulletproof algorithm in less than an hour.  I just think there is some careless engineering going on.

I think you may have misread my post. As I said, I've never found tangent snaps in VW very reliable 🙂

There's definitely room to improve the current snapping system.

Kevin

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1 hour ago, Kevin McAllister said:

There's definitely room to improve the current snapping system.

Glad you agree!  You may recall a thread a while back where users tackled the question of how to draw an arc tangent to given points on two circles.  We found a solution and proof to that problem, and though we can construct such an arc using techniques similar to how you typically draw tangent lines, it escapes me why these basic calculations can't be reliably incorporated into VW tools.  BTW, although I find that the problem that started this thread does not exist for me in v2017, Mike has found that it does.  So something a bit arcane is going on.

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On 1/6/2020 at 9:44 PM, P Retondo said:

So something a bit arcane is going on.

Maybe it is a secret test to find out if a tool or functionality is actually being used, i.e. if there is an obvious failure and nobody is complaining then the tool/functionality is probably not used and could then be removed or no longer developed in favour of another tool/functionality. 😁

Though I may have risked waking up a sleeping dog with this comment.🙊

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Posted (edited)

Disheartening to say the least to have to go into a completely different 2D CAD program to do intuitive, smart 2D CAD layout, then import it into VW. The "smart points" snap isn't, and the tangent snap does not actually appear in most cases. And the symbols that are supposed to show you how to use the tool are arcane as noted.

I am trying to get it to work with an "oval" (which should properly be called and ELLIPSE tool) with arcs, and it does not work.

Quick, intuitive 2D layout is critical to get the geometry and math needed for a lot of things, even (or especially?) in a 3D environment. Really looking forward to VW applying some resources to modernize their UI in this regard.

Edited by geo44rey

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