Rotation expression for stopwatch

Adobe After Effects Expressions

Rotation expression for stopwatch

Posted by Michele Busiello on January 26, 2011 at 2:43 pm

hi guys!

i have an expression question which is so basic that i’m almost ashamed asking it 🙂
here it comes:
how do i build a rotation expression for a stopwatch hand ? i know there are tons of web-tutorials explaining how to set up an expression for a clock hand. but as opposed to those tutorials i DON’T want the clock hand to rotate smoothly. since it ist a stopwatch and not a clock the hand should rotate in a “jagged” fasion. like so: https://www.youtube.com/watch?v=23wsGQx5wZE

how do i achieve that ?
thx in advance!

Dave Irion replied 13 years, 7 months ago 3 Members · 6 Replies
6 Replies

Kevin Camp
January 26, 2011 at 3:56 pm

i don’t now what kind of control you want to have for it, but this will ‘tick’ the second hand every second, with no interpolation between ‘ticks’

linear(Math.floor(time)%60,0,60,0,360)

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW
Michele Busiello
January 26, 2011 at 4:11 pm

thx for your reply!
your solution works good and is going to the right direction. this expression is restricted to one tick/second though. is there a way to control the amount of ticks/time ?
Kevin Camp
January 26, 2011 at 4:18 pm

if you just wanted to key frame the rotation value but limit the values to increments of 6 degrees, you could try something like this:

Math.floor(value/6)*6

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW
Kevin Camp
January 26, 2011 at 5:28 pm

or maybe you just wanted to use time, but wanted to have a hand that moved in 100ths of a second…

linear((Math.floor(time*100)/100)%1,0,1,0,360)

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW
Kevin Camp
January 26, 2011 at 5:45 pm

this might be a little more intuitive…

set the tickUnit to be the duration of a single tick.. so if you needed to tick each second, the value would be 1; every 10th of a second would be 1/10.

set the period to be the amount of time (in seconds) that it takes for a hand to do a full 360 degree sweep. so for the second hand the value would be 60 (60 seconds to do a 360); for a 10th of a second the period would be 1 (1 second to do a 360)…

tickUnit = 1/100; // duration for a single tick (in seconds) period = 1; // duration for a full sweep of the hand (in seconds)
linear((Math.floor(time/tickUnit)*tickUnit)%period,0,period,0,360)

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW
Dave Irion
September 25, 2012 at 3:25 pm

Thanks for the great expressions. But I have a specific problem that I could use help on.

I used this expression

linear(Math.floor(time)%60,0,60,0,360)

and it works great. But Is there a way to have the expression take a certain amount of frames to complete the rotation with an ease?

So instead of the movement of the rotation happening instantly it would happen say over 10frames?

Thanks

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