Is there an AE expression that can provide the same function as a driven key in Maya?

[Dan Ebberts]

It sounds pretty much like one of the things you can do with expressions: link two properties together. Maybe I’m not getting it.

BTW – I couldn’t get your link to work.

Dan

[Francis De la torre]

Hey Dan,
sorry for my lack of articulation. The function is very difficult to explain verbally. If you can imagine using a slider expression controller, and linking any attribute on several other objects to the slider. Now when slider vaule= 1, all objects have a specified set of attribute values (position, rotation, transparency, effect attribute value, etc); when slider value= 2, all objects have a new specified set of attribute values; when slider value= 3, all objects have a new specified set of attribute values, etc.

Now when I animated the slider value, the other object attributes, animate between their specified set of attribute values.

That in a nutshell is what a driven key does in maya.

Thanks for the help Dan.

[Dan Ebberts]

I think the best you could do would be to apply a slider to a layer (named “control” in this example). Then, for each property you want to control, you’d need to apply an expression like this to remap the slider range to the parameter range. This rotation example is set to go from -10 to +50 degrees as the slider goes from 0 to 100:

slider = thisComp.layer(“control”).effect(“Slider Control”)(“Slider”);
sliderMin = 0;
sliderMax = 100;
myMin = -10;
myMax = 50;

linear(slider,sliderMin,sliderMax,myMin,myMax)

Dan

[Dan Ebberts]

I thought of another way, if you need access to the values and you don’t want to edit the expressions all the time. In fact, this way you could use the same expression for all your parameters. The idea is that you would set a keyframe at time zero for the parameter value you wanted to correspond to 0 on the slider. Then you’d move forward one frame and set a value corresponding to the slider’s 100. Then apply this expression to the parameter:

slider = thisComp.layer(“control”).effect(“Slider Control”)(“Slider”);
sliderMin = 0;
sliderMax = 100;
myMin = valueAtTime(0);
myMax = valueAtTime(thisComp.frameDuration);

linear(slider,sliderMin,sliderMax,myMin,myMax)

Dan

[Francis De la torre]

Thanks Dan. I really appreciate you taking some time to chew on this. I will give this method an attempt, and see where the results land.

[Francis De la torre]

Just saw your second post. This is exactly how it works in maya! The attributes controlled by the driven key are assigned a timeline keyframe starting at frame 0 and moving forward in 1 frame increments (these timeline keyframes carry no actually animation, but are simply references for the driven key). Each frame increment relates exactly to the value placed in the driven key. So value 1 on the driven key looks at frame 1 for the keyed attributes. The expression solution you provided sounds exactly like what I am looking for. I will test over the next couple days and report my results.

Thanks Again!

The Best

F De La Torre
http://www.francisdelatorre.com

[Peakash Patel]

Hi Dan,

Sounds like a great solution. I’m a maya user and use set driven keys a lot.

I’m trying to use your solution at the moment and am having trouble figuring out how to hook it up etc. Any help would be appreciated.

 

Kind regards.

 

Peakash

[Dan Ebberts]

Having never used Maya, I’m not sure how much help I can be…

[Peakash Patel]

Hi Dan,

I was wondering how to connect up in After Effects?

I seem to be getting Syntax errors etc.

Do you have an example file?

Kind regards.

Peakash

[Dan Ebberts]

Add a null to your comp, name it “control” and add a Slider Control to it.

For whatever property you’re animating, set a keyframe at time = 0 for the initial value, go forward one frame and set a keyframe for the final value. Then add this expression (don’t use the code from 2008–it got trashed when they updated the site)_:

slider = thisComp.layer("control").effect("Slider Control")("Slider");
sliderMin = 0;
sliderMax = 100;
myMin = valueAtTime(0);
myMax = valueAtTime(thisComp.frameDuration);
linear(slider,sliderMin,sliderMax,myMin,myMax)

The slider should then control the animation.