Michael Mirn (michaelmirn)

6 answers · asked · Lesson: Rolling Ball · Course: Blender Animation Bootcamp

How to avoid "Too slow / Too fast" rotation tip

It's quite easy.
Select your object, look at its height, divide that by 2. That's a radius.
Use that number to calculate the circle of your ball (2 *3.14 * radius).
That's the length of the path your ball has to pass from point A to point B to rotate 360 degrees sharp. Just measure it on the X-axis.

  • This only holds true while speed is constant. If there is any acceleration, the math gets a little more complicated, but it is a good place to start and get a figure for total rotation. If you want to be real precise you would need to get distance travelled each frame and find the angle of rotation that would give you the corresponding arc length. It’s possible to automate this (and many good rigs will), but the point of the exercise here is to train your eye. 

  • You are right.
    And yes, sure, you could divide and multiply any kind of frames and angles.

  • crew

    Yep the point is 'training'.  It will train your eye as well as build your skills with the GE.

    You should never have to do something like this in 'the real world' haha



  • Apart from everything that has already been said here: why do you divide the height by 2 to get the radius and then immediately multiply that radius by 2 again, without ever using the radius???

    Computers are really fast at calculating, but there is no reason to let them perform unnecessary math operations;)

    • "Apart from everything that has already been said here: why do you divide the height by 2 to get the radius and then immediately multiply that radius by 2 again, without ever using the radius???"

      Since the initial formula is 2π R. Just a safety measure so nobody would ask "where this radius came from?"
      Don't think you need a computer to calculate that.

  • Thanks for the tip!