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expressions mysteriously turning themselves off….!?
why would AE — spontaneously and without any error message — turn off an expression?
i’ve got an expression applied to a layer and i duplicate the layer several times (actually a few hundred times), to generate position and scale values, sometimes other values. i scroll through all of my layers and i see that on a few of these layers, for no apparent reason, one or more expressions have been deactivated.
why would this happen?
and is there a way to prevent it from happening?thanks in advance
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7 Replies
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Which version of AE? What do the expressions look like?
Dan
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this has happened to me both in 7.0 and cs3 beta.
i’d rather not post the code — top secret project — but basically, it’s a way of defining a 3d motion path with one layer (which i call refObject), and then having any number of other layers evenly distribute along that same path, and then animate their distribution. so if i happen to change the motion path for the refObject, all other layers will adjust accordingly.
to create the pattern of distributed layers, all i have to do is duplicate one of the visible layers as many times as i want. but the weird thing is, the expressions i’ve applied to position and other properties on these layers will mysteriously and without any error message Turn Themselves Off.
i’ve noticed that this is more prone to happen if these comps have more than 100 layers. does AE freak out if a comp has that many layers?
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>does AE freak out if a comp has that many layers?
I set up a similar thing (lots of layers following a leader on a 3D path) for a tutorial I did for the Meyers’ CMG Vol. 2, without any issues like you’re seeing.
If you’re doing something silly like having each layer reference the previous one, you might trigger and expression engine timeout, which will indeed disable some expressions, but you should get an error message.
Other than that it’s hard to say without seeing your code. All I can say is that I’ve never seen the symptoms you describe.
Dan
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Another bug I encountered today:
AE sometimes disabled expressions saying there is no ‘active camera’ (I used thisComp.activeCamera). Cameras abound all over the place 😎
Changing it to a direct pickwhip to the specific camera solved it.Never had that problem before.
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Ah, that triggered a memory. I’ve had expressions generate inappropriate errors when I’ve got the graph editor up, because the graph editor displays values before and after the comp. So if you opened the graph editor with an expression refering to the active camera, I’d guess it might generate an error since it likely doesn’t exist before the first frame.
Dan
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I have had expressions mysteriously turn off before…I recently did a project in the AE CS3 beta where I had about 1600 images arranged in a grid and each layer was using the new sampleImage() function to sample the alpha value of a logo so that some layers appeared like a mosaic of images in the shape of a logo. After about 1000 duplicates, some new duplicates would have its opacity expression turned off, and I would get no error message. To workaroud this I selected all my layers, right clicked, and went to reveal expression errors” and then turned back on all the disabled expressions, and everyhting worked fine.
~Colin -
i had the same thing with this expression:
delta = toWorld(anchorPoint) – thisComp.activeCamera.toWorld([0,0,0]);
radiansToDegrees(Math.atan2(delta[0],delta[2]))I solved it by moving the camera to the left, in the timeline. So that the camera would exist before frame 1.
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