Rotating items, start and end angles

[J4BPX]

Does anybody else find it odd that when rotating an item that for a positive angle rotate (say 20°) the item is rotated anticlockwise?  On any compass turning 20° would turn you right or clockwise?  Is this some sort of strange design convention that I don't know about or a setting that I can't find because this is not logical in the real world..  Similarly the start and end angle when drawing a  donut bear no relation to 360° (or vertically up the screen) that I can figure out?  And if you increase the start angle it also moves anticlockwise - which in the real world should be a decrease in angle?  Can anyone enlighten me because what should be a simple mental calculation - I want the donut start angle at 225° and the end angle a 135° becomes a nightmare of dragging the ends around until it looks roughly right then looking at the angle Affinity design is using and then guessing whether to add or subtract degrees to achieve accuracy.  It's doing my head in!

[Dan C]

Hi J4BPX  

I recommend reading the below post regarding positive rotation being anti-clockwise:

 

In regards to the donut, I'm not entirely certain for the design reason, but the start and end angle work along the horizontal axis. If you wish for the start point to be vertical up your screen, simply rotate the object by 90°, once rotated, a start angle of 225° and an end angle a 135° (270° total) would look as such:

I hope this helps  

[Pšenda]

5 hours ago, J4BPX said:

On any compass

The compass is used to determine the azimuth/direction, not to determine the angle/deviation from the X axis.

[J4BPX]

Still doesn't make sense to me.  Any angle deviation from the x axis............any increase in value should surely be clockwise?  Why should Designer be different from any other angular application or calculation?  It only makes a little sense if you are saying that when an item is rotated by 20 degrees that the 20 degree azimuth is now the vertical or horizontal (or whatever datum you start with).  But that is completely at odds with any other application of rotation I have seen.  It also makes further calculations of rotation by increments more difficult than it needs to be.   Anybody got a logically explanation?  Why is this way a good idea?

And why have to rotate the donut by 90° to make the start and end angle work? ?????

[R C-R]

13 hours ago, J4BPX said:

Any angle deviation from the x axis............any increase in value should surely be clockwise?

As was mentioned in the linked topic, Affinity follows standard mathematical conventions for angular rotations. So for example, in the two dimensional Cartesian coordinate system, there are four quadrants numbered in a counter-clockwise direction. In the trigonometric Unit circle definition, the angle from the x axis increases in a counter-clockwise direction for increasing positive values, as the Wikipedia animation demonstrates.

So for example, if say you want a donut with start angle of 225° relative to clockwise rotation, you need to subtract 225 from 360, which yields 135° for the start angle relative to counter-clockwise rotation. You can let the app do the math for you by entering "360-225" in the Start angle field.

[Pšenda]

16 hours ago, J4BPX said:

Why should Designer be different from any other angular application or calculation?

For example AutoCAD (http://tutorial45.com/angles-and-lines-in-autocad/).

 

[J4BPX]

So basically:  0° is the x axis and any positive rotation of an item rotates it toward the y axis?  How annoying.........

[R C-R]

34 minutes ago, J4BPX said:

So basically:  0° is the x axis and any positive rotation of an item rotates it toward the y axis?

Basically yes, although technically positive rotation begins on the positive x axis & rotates through the four Cartesian quadrants in a counterclockwise direction. The same conventions are used in most mathematics, science, & engineering applications.