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valueAtTime property gives “undefined” error
The goal is to vary an effect’s property using the layer’s horizontal velocity, caused by animating its anchor point.
My thinking is that the expression
transform.anchorPoint[0]-transform.anchorPoint[0].valueAtTime(time-(1/24))
Should give the horizontal velocity for the frame.
But while just
transform.anchorPoint[0]
or just
valueAtTime(time-(1/24))
don’t return errors,
transform.anchorPoint[0].valueAtTime(time-(1/24))
returns the error
“Function transform.anchorPoint[0].valueAtTime is undefined”What am I doing wrong?
transform.anchorPoint[0]-transform.anchorPoint[0].valueAtTime(time-(1/24)) -
4 Replies
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try valueAtTime(…)[0] instead.
BTW, anchorPoint.speed is more general (you don’t have to write the frame rate).Xinlai Ni
Software Engineer, Google Inc. -
I thought “speed” would give the actual distance moved, whatever the direction, while I need just the horizontal component.
Your “try valueAtTime(…)[0] instead” tip confused me for a while, but it clicked: valueAtTime is a property, so it needs to come before specifying the dimension.
“transform.anchorPoint[0]-transform.anchorPoint.valueAtTime(time(1-24))[0]”
is working. Thanks!
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How about just this?
transform.anchorPoint.velocity[0]
Dan
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When I RTFM I find that “speed” always returns a 1D, positive value, but”velocity” returns a result w/ the same dimension as the property.
So thanks, Dan; a more elegant solution.When I plug it in, the results are similar but not identical–perhaps a matter of which chunk of the timeline is being sampled; my original math samples the frame before, “velocity” is probably the value at the instant of the frame start.
At least now the expression functions. Onward–and thanks again, guys.
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