With a lot of Shachar's AWESOME help, I've learned how to use the AEGP suite to pull the position (for example) of the active layer and use it.
With this additional code snippet contributed by Zewt, I've been able to pull that info from another layer using a PF_Layer_Param. Awesome!
My intention was always to produce a similar effect to an After Effects constraint. For example, let's say we have a point parameter as part of an effect on one layer, and a NULL on another. In AE, I can simply lasso the point parameter to the NULL's position and wherever I move the NULL, the point parameter will follow interactively.
I was trying to accomplish the same thing using the SDK. Pull the position of a NULL from another layer, and apply it to my point parameter.
I've managed to do that, but it's not interactive. Meaning, if I move the NULL, my effect's point parameter won't move until I go back to the effect layer and adjust any of the effect parameters. Then I see the point parameter 'jump' to the NULL's position.
So is this how AEGP effects work? They do not continuously pull info? If I wanted to achieve an effect like the one I described above where I link a point parameter to a NULL and be able to move the NULL around with the point parameter following, is there a different approach I should be using?
it gets very tricky. you'd have to create an invisible param with an expression on it, tying the param's value to the desired dependent parameters so any change in them would create a change in the param value that would trigger a re-render.