just how to use “speed”

[Andy Engelkemier]

well I got it to work, but still would like to know how to get it to work using speed.

I’m using 24fps so wanted to get the position 1/2 keyframe back to calculate from.

I thought you could do: position[0].valueAtTime…
but that gave me an error, so instead I put a variable to it, then called the variable’s first value instead.

Also for some stupid reason I couldn’t get the syntax right for just calling thisLayer. I thought it was suppose to be: thisComp.layer(thisLayer)…
After failing at that I said, “F it” and just put the layer name instead just so the expression at least works right now.

Here’s what I used. I’d still love some help though.

posOld = thisComp.layer("timeline box").position.valueAtTime(time - (1/48));
(posOld[0] - transform.position[0])*-5;

[Dan Ebberts]

I think this is all you need:

transform.position.speed

thisLayer is assumed, so you don’t need to specify it.

Dan

[Andy Engelkemier]

hmmm, so what am I doing wrong then. Given that I’m applying it to a single digit I need to break it down to only one number of the array, so I did this, but it doesn’t work.
expression error. Can you spot anything wrong with it?

also can you do things like:
transform.position[0].speed

That was the first thing I tried as a single line, but AE didn’t like it.

p = transform.position.speed;
p[0];


[Dan Ebberts]

.speed is a one-dimensional attribute. If your layer is only moving in the x-direction, transform.position.speed should give you what you want. If it’s also moving in the y direction and you just want x, you would use the x component of .velocity, like this:

transform.position.velocity[0]

Dan

[Andy Engelkemier]

so I guess I was unnecessarily trying to make it much harder than it really was. For some reason I was thinking it would give speed for multiple directions and I was thinking velocity was more complex than just speed in both directions. I suppose that’s all you need to define the vector of a 2D movement.

It’s working now. Although, I’m not sure why you can’t specify the first value in an array of 1. I know that’s dumb, but couldn’t the computer still figure out that you want The value?

I wish I could find some good online resources so I didn’t have to keep bugging you. I’m not a fan of books because it takes too long to search through to find something specific. Although, I suppose since I’m not specifically calling you out, you Are helping voluntarily. And for that, I thank you.

[Dan Ebberts]

>I’m not sure why you can’t specify the first value in an array of 1.

You can, if it’s stored as an array (which speed isn’t). In general, one-dimensional properties and attributes are stored as scalars and multi-dimensional properties and attributes are stored as vectors (arrays).

Dan