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Rotate - why does a positive number rotate counter-clockwise and a negative number rotate clockwise?


yasin2ray

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I think it’s the method that all CAD programs use. It’s to do with mathematics and the Polar coordinates system which always go counter-clockwise. 
 

I am sure someone else will be able to elaborate with a more academic explanation but I accepted it long ago and have got used to it!

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502515614_ScreenShot2022-03-08at11_44_09AM.png.9b055600e9ecbc16fb7fed0a5271bd0e.png

 

Like Mark said it's based on Polar Coordinates, with 0° equating to the positive X axis. If you look at the 30° line in the graphic above you can start to see why positive values correlate to moving "counter-clockwise." It helps to picture this chart rather than a clock when thinking about rotation.

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24 minutes ago, Andy Broomell said:

502515614_ScreenShot2022-03-08at11_44_09AM.png.9b055600e9ecbc16fb7fed0a5271bd0e.png

 

Like Mark said it's based on Polar Coordinates, with 0° equating to the positive X axis. If you look at the 30° line in the graphic above you can start to see why positive values correlate to moving "counter-clockwise." It helps to picture this chart rather than a clock when thinking about rotation.

Hmm! Okay, thank you! I bet I haven't thought about that since high school.

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14 hours ago, Andy Broomell said:

502515614_ScreenShot2022-03-08at11_44_09AM.png.9b055600e9ecbc16fb7fed0a5271bd0e.png

 

Like Mark said it's based on Polar Coordinates, with 0° equating to the positive X axis. If you look at the 30° line in the graphic above you can start to see why positive values correlate to moving "counter-clockwise." It helps to picture this chart rather than a clock when thinking about rotation.

 

It seems like mathematicians just being awkward by adopting a convention that is different from the one we all know from a compass.

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But vwx is inconsistent with rotational direction:

 

I think i found another reversed rotation in a different tool 

 cant find it. I think counter clockwise should be positive rotation. If new tools or nodes break existing , then just add a new “corrected” tool or node?

 

-B 

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18 hours ago, line-weight said:

 

It seems like mathematicians just being awkward by adopting a convention that is different from the one we all know from a compass.


but what if you are calculation angle of elevation from horizon?  Doesn’t the positive x axis being 0 degrees make perfect sense?  Putting it all into perspective, we need both azimuth and elevation conventions for angular measure 😉

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5 hours ago, jeff prince said:


but what if you are calculation angle of elevation from horizon?  Doesn’t the positive x axis being 0 degrees make perfect sense?  Putting it all into perspective, we need both azimuth and elevation conventions for angular measure 😉

 

Well, the horizon is a very slight curve, whereas a plumb line is straight. If we are calculating an angle relative to the horizon, what we are really calculating is angle relative to a line perpendicular to the direction of gravity/a plumb line.

 

Therefore I'm going to argue that taking vertical as our 0 degrees reference makes more sense - and it also corresponds with what most people are used to; compass directions.

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2 hours ago, line-weight said:

 

Well, the horizon is a very slight curve, whereas a plumb line is straight. If we are calculating an angle relative to the horizon, what we are really calculating is angle relative to a line perpendicular to the direction of gravity/a plumb line.

 

Therefore I'm going to argue that taking vertical as our 0 degrees reference makes more sense - and it also corresponds with what most people are used to; compass directions.


 

Architects vs astronomers 🙂

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This is very educational for me, thank you to all contributors. For me, this "reversal" seemed to happen a SP or two ago where a Rotate 45 caused a Counter-Clockwise rotation.

While I figured it was a bug, I know know why this happens and have since gotten used to it.

Thanks again.

 

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19 minutes ago, FlyingHoward said:

For me, this "reversal" seemed to happen a SP or two ago where a Rotate 45 caused a Counter-Clockwise rotation.

This has always been the way things have worked in both Vectorworks and AutCAD. It is a CAD convention which is just one of those things. As I said above, it is something you just get used to over time and I rarely find it a problem anymore.

 

Here is the source of your pain!  https://en.wikipedia.org/wiki/Polar_coordinate_system

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Then I would ask why the menu icon representing the rotation tool shows the arrow in a clockwise direction?

That would imply that a positive entry would rotate the object clockwise. 🤷‍♂️🤣😂🤣

Edited by LarryO
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On 8/11/2022 at 4:27 PM, LarryO said:

Then I would ask why the menu icon representing the rotation tool shows the arrow in a clockwise direction?

That would imply that a positive entry would rotate the object clockwise. 🤷‍♂️🤣😂🤣

THIS. As well, the description of the Rotate Tool should say something about polar coordinate rotation.

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