Object Rotation Direction vs Compass / Cardinal Directions


#1

Is it just me or does it seem counterintuitive that Object Rotation Directions are reversed vs Compass / Cardinal Directions? Is there some logic to this that I’m missing?
Best, Bill


#2

Yes, mathematical logic… In a mathematical right handed Cartesian coordinate system, 0 degrees is along the positive X axis, and positive rotation is counter clockwise… Since construction of 3d geometry is based on this kind of mathematics, it is logical that Rhino should use it…

–Mitch


(Pascal Golay) #3

Rotation is based on the unit circle where 0 degrees is at ‘3 o’clock’ or the X axis, and pi/2 or 90 at ‘12 o’clock’, or the Y axis, etc. That is, ‘+’ is counter clockwise if the axis is pointing towards you.

-Pascal


#4

Ahhh Yes, I have vague recollections of this from 8th grade geometry!
It also slipped my pea brain that Cartesian Coordinate System was invented by Descarte.
Here is the relevant Wiki that I used to RTFM: http://en.wikipedia.org/wiki/Cartesian_coordinate_system
Thanks for the clear & concise explanation Mitch & Pascal

Best, Bill


#5

You, of course, meant to say "…’+’ is counter clockwise if the Z axis is pointed toward you. We all knew that. :smile:


(Pascal Golay) #6

Hmm- well, I should have specified ‘rotation axis’- is that more like it?

-Pascal


#7

It’s a right PITA for us sailors who have to re-boot our brains every time we get back on the boat after being in CAD land.
But, you get used to it :wink:


(Pascal Golay) #8

Just like sea-legs, right?

-Pascal