The linear method is, hands down,
my favorite expression. You'll find it extremely useful when combined
with expression Slider Controls. If you've ever used a Cinema 4D Range Mapper,
you'll love this expression. The linear method is a tool
for converting value ranges. It starts with the word linear, and includes
three to five arguments, wrapped in parenthesis and separated by commas. The first argument is always a custom
input source, which can be time, value, or another property reference. The basic method uses three arguments, with
the second and third arguments representing the output min and max values as the
input value changes from 0 to 1. The long-form version is more flexible,
and it accepts five arguments. The second and third arguments become input
min and max, while the output min and max are moved to the fourth and fifth arguments. Let's say you wanted to pair the Rocket's
animation to a Rocket Launch Slider Control. By using a linear method, you can map
the expression Slider Control to the Rocket's Y Position value. In this example, you'll notice a Controller
layer which contains an expression Slider Control named Rocket Launch. If you open the Position property on the Rocket
layer, we can use the pick whip to select the Rocket Launch Slider Control. So, because we're only going to work with
the Y axis, I'm gonna right-click Position, and separate the dimensions
so we can get all three here. Then, add a new expression to the Y Position
property, and then highlight the control so that we can see the
Rocket Launch Slider Control. Now, come down and grab the pick whip and
drag it up to the Rocket Launch Slider, and let go, and it's gonna give us the reference
to the Slider right here as automatic syntax. This reference is gonna serve as our
linear function's input. So, at the very beginning of this comp, I'm
gonna start the linear method by typing linear, open parenthesis, and then coming to the very
end of the Slider at the end of the reference, and adding a comma. So this is our first argument. For the second argument, which is the Slider's
minimum value, I'm gonna type 0, comma, and then the max value,
I'm gonna just use 100, comma. You'll also need to specify
the output min and max. So, immediately after 100, you're gonna create
a fourth argument, which is gonna be value, to reference the original value of the Y Position,
followed by another comma. And then the fifth argument is gonna be value,
followed by a subtraction operator, and I'm gonna use a value of 1500 for this,
so we're gonna subtract 1500 from the Rocket's Position as the
Slider goes from 0 to 100. And then finally, at the very end you'll wanna
close the parenthesis. And if you click off the expression field,
you'll notice that nothing's changed because your value is still set
to 0 on the Rocket Launch. But if you change this to 50, which is halfway
between our min and max, and hit Enter, you'll notice the Rocket has now
moved up in the sky. And then, if you change this to 100,
it will complete its animation. You can also slide the Rocket Launch
slider, and it's gonna animate between the min and max values
that you specified. The coolest part about this is, because we're
using the value as a relative reference, you can actually select the Rocket layer
and move it anywhere in your composition. I'm gonna put it right here
behind this mountain. And, if you come back up to the Control, and
now if you slide the Slider value from 0 to 100, the Rocket still animates 1500 pixels
on its Y axis because it's using value as its starting position
instead of a hard-coded value. Now, let's look at a couple variations
of the interpolation method. These methods can be used interchangeably
with linear to change how a value is remapped. All you have to do is replace linear
with these method names. The first one we are gonna look at is the
ease method and it's gonna add a standard ease in and ease out at the beginning
and end of the value range. It behaves just like the Easy Ease
keyframe function in After Effects. And so if you come in and change linear to ease,
and click out of the expression. And then if you come up to the Control layer,
set a keyframe at 0, come forward in the composition and set a keyframe to 100, you can
then look at the Post-Expression Graph to see how this value's changing. Now, even though we have linear keyframes
on this, we didn't actually apply Easy Ease to the Control layer, we're still getting a nice
ease and that's because of the expression. If I was to come in here and change this back
to linear, like we had before, and click away, now the value change is linear and it
no longer has the ease curve. Two other variations of this are easeIn and
easeOut, and they are identical to the ease method, except they only provide
ease interpolation at either the beginning or the end of the output range. So, if you come over here to the ease function
and simply add In, with a capital I, and click on the Post-Expression Graph,
and open the Graph Editor, you'll see exactly what this value is doing. It has a nice ease in at the beginning,
and switches to a linear at the end. And if I select Y Position and change this to Out,
capital O, and click away from the expression, it just switches how the
ease is interpolated. So now, the linear keyframe is at the beginning,
and it eases out at the end of the value range. You can find the linear and ease syntax in the
Expression Language Menu under Interpolation. We've arrived at the end of Lesson 205:
Remapping Values with the Linear and Ease Methods. If you enjoy this expressions course,
consider purchasing the paid content. It includes in-depth documentation,
extra tutorial content, high definition videos, and all the project files used in the training. Your purchase will help to create more
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