Apple Motion tip: Using negative offsets for Ramp curve control
When learning Apple Motion I suggest that people avoid using keyframes to animate parameters. Motion is much happier using behaviours to change values over time.
This tip is for Motion users who have a good understanding of how to use behaviours to control animation.
A popular parameter behaviour is Ramp. Over the time of the behaviour it animates a parameter from one value to another. In this case, at the start of the behaviour, 180 degrees is added to the rotation parameter and this value changes to adding 0 degrees by the end:
The Curvature value of 100% means that the value eases out from 180 and eases into 0. Here’s the animation graph:
Unlike some behaviours you cannot directly set a curve shape using Ramp. In many cases you need to have a curve that eases in only or eases out only.
Using this tip, you get more control over the animation curve.
In this case I would like the curve to ease in to the value of 0 degrees. You can do this by using a negative Start Offset value.
A negative Start Offset extends the animation curve back in time and throws away the first part before the start of the behaviour. In this case the behaviour is 25 frames long (counting from frame 0 to frame 24). If we set the start offset to -24, the animation graph will start 24 frames before the start of the behaviour. Given that the Start Value of the behaviour is 180 degrees, if we double the length of the graph, by the time it is half way through (at frame 0), the value will be 90 degrees. If we want the value of the graph at the start of the behaviour to be 180 degrees, the Start Value needs to double to 360 degrees:
Here’s what the parameter animation graph looks like using these parameters:
The curve is constant at the start when the value for rotation is 180 degrees, and eases into the end value of 0 degrees.
If little of this makes sense to you, check out the Motion 5 Fast Forward tutorial from Ripple training.
Also consider tuning into my episode of the free Moviola webinar series: Creating Final Cut Pro X Effects Using Apple Motion 5 on January 8th, 2013.
Just what I’ve been wanting to achieve.
Thanks so much
I imagine there are less than 100 people on Earth who will appreciate this tip, I’m glad you got to read it!