Positive y is up and angles

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debenriver
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Positive y is up and angles

Post by debenriver » Thu Jun 25, 2015 1:48 pm

Hi Eric

Something odd is happening to Angle on the Edit pallet when "positive y is up" is selected in the Preferences.

I draw a line from top to bottom – normally this would be 90º. With positive y is up, the angle shows as 270º.

I actually want my line to be at 35º to the vertical, so normally I make the angle 125º (90 + 35) in the Edit pallet and my line rotates 35º from the top end.

With positive y is up selected, it looks as if the angles are getting smaller as you rotate clockwise – so I enter 235º (270 - 35). But I get a line at 125º (that is at 35º to the vertical from bottom to top). And the angle shows as 125º in the Edit pallet, even though I entered 235º. To get what I want, I have to enter 125º and the Edit pallet then reads 235º and my line is at 35º.

With the same line – vertical from top to bottom - reading 270º -- if I enter 90º, nothing happens (I don't think the line reverses). Edit stays at 270º.

I don't know if this is a bug or I am failing to grasp the geometry here!

George

Eric Pousse
Posts: 668
Joined: Sat Dec 03, 2011 12:31 pm
Location: Tours - France

Re: Positive y is up and angles

Post by Eric Pousse » Fri Jun 26, 2015 6:28 am

Bonjour George

It is because the angles are calculated from the beginning of the lines.
If you draw a line from top to bottom, the angle is 270° (with y up positive)
But if you draw the line from bottom to top, the angle is 90°.
You can see the angle when you drag the line. If you move the end, you can see all angles.
I think that it is logical to do like this.

Cordialement.
Eric Pousse

debenriver
Posts: 462
Joined: Sat Dec 03, 2011 9:19 pm
Location: Maine USA and Suffolk England
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Re: Positive y is up and angles

Post by debenriver » Fri Jun 26, 2015 2:06 pm

Hi Eric

I think I didn't write the question very clearly.

Say I want to draw a line at 35º drawing from top to bottom, with the top of the line inclined to the right. With Positive y is Down (original situation), I would need to draw a line at 125º.

So I draw my line at approximately 125º and then I edit it by entering 125 in the Angle box in the Edit pallet. Left hand image below. I click Enter and my line will be at 125º and it will show A = 125 on the Edit pallet. Right hand image below.
Screen Shot 1.jpg
Screen Shot 1.jpg (15.72 KiB) Viewed 3979 times
Now to do the same thing with Positive y is Up, I need to draw a line at 235º. So I draw a line approximately at 235º and then I edit it by entering 235 in the Angle box in the Edit pallet. Left hand image below. I click Enter and I don't get the result I want at all. I get a line showing A = 125º Right hand image below.
Screen Shot 2.jpg
Screen Shot 2.jpg (14.88 KiB) Viewed 3979 times
To get what I want I have to enter 125º in the Angle box in the edit pallet, even though the Edit pallet is showing A = 238.xxxx. Left hand image below. Then when I hit Enter I get what I want: a line at 235º and it shows as A = 235 in the Edit panel. Right hand image below.
screen_shot_3.jpg
screen_shot_3.jpg (15.15 KiB) Viewed 3979 times
So what I am saying is that it behaves very differently with Positive y is Up in that it is difficult to work out what angle to enter. And the angle entered and the angle recorded in A = xxx are different. Whereas with Positive y is Down it behaves quite logically and the angle entered and the angle recorded in the A = xxx are the same.

With Positive y is Down, if you draw a vertical line top to bottom it shows as 90º. Enter 91º in the Angle box and the line rotates 1º and changes to A = 91º. Enter 92º and the line rotates 2º and changes to A = 92º and so on. All fine and dandy :D

With Positive y is Up, if you draw a vertical line top to bottom it shows as 270º. Fine no problem with that. Enter 91º in the Angle box and the line rotates 1º and changes to A = 269. Enter 92º and it rotates 2º and changes to A = 268 and so on. Not so logical surely :?: You should be entering 269 to get the line to rotate 1º from 270º, to A = 269. And 268 for 2º, A= 268, and so on.

Cheers -- George

Eric Pousse
Posts: 668
Joined: Sat Dec 03, 2011 12:31 pm
Location: Tours - France

Re: Positive y is up and angles

Post by Eric Pousse » Fri Jun 26, 2015 2:35 pm

Yes George, now I see the problem.
I will fix it and post a new beta.

Thanks.
Eric Pousse

debenriver
Posts: 462
Joined: Sat Dec 03, 2011 9:19 pm
Location: Maine USA and Suffolk England
Contact:

Re: Positive y is up and angles

Post by debenriver » Fri Jun 26, 2015 4:01 pm

OK - great!

Will you look at parallels in (possibly?) DXF drawings – see Attributes post – at the same time?

Cheers -- George

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