-
Control Choke Intensity with Layer Alpha
I am trying create a wipe in which a layer’s alpha is unchoked from left to right, so that it appears to grow on. I’ve tried isolating the area I want choked with a matte, but cannot figure out how to drive the choke so that its intensity is responding to the alpha, not just fading up from no choke to full choke, which is what happens when I feather the alpha. Is there a way to link the simple choker to the alpha channel of the matte so that it chokes in degrees from 0-10 based on the alpha’s 0-1 value?
-
2 Replies
-
Grow meaning go from choked to un-choked. Thin to thick. Effect-on to effect-off. But asymmetrically across the text so it if the word were “WORD”, then ‘w’ would start unchoking first, then ‘O’, then ‘R’, then ‘D’, but the thickness should also grow across the letters from one side to the other, not just one character at a time, so I would rather stay away from animating the per character stroke property in the text.
The way I’ve been trying to do it is building a matte with a ramp inside a pre comp, animated laterally with the position property. This is placed above an adjustment layer that is luma matted to it. This doesn’t work because the adjustment layer opacity is what is being controlled by the pre comp, not the intensity of the effect on the adjustment layer, so instead of getting varying width of choke, I get varying opacity of effect layer, effectively mixing between full choke and no choke across the area of the ramp.
Let me know if there’s anything else I can be more specific about. Thank you!
-
Thanks David, that makes sense. I was hoping for something like an expression that would tie the choke value to the pixel alpha/luma value in the matte, but couldn’t figure out a script that would look at each pixel in the layer discreetly.
i.e. if the alpha at a given pixel is .5 the choke effect would be 50%. If it’s .75 ten pixels up, then that pixel is 75% of the effect and so on.
Reply to this Discussion! Login or Sign Up