Controlling the amount of an effect with gradients and/or masks?

[Roland R. kahlenberg]

You’re talking about Compound Effects. By definition, a Compound Effect takes information from a second (and sometimes third) layer to drive an effect. The information is normally in the luminance values of the secondary layers.

These values are then used to affect the intensity and/or location of the effect.

Not all effects are Compound Effects. Turbulence Displace isn’t a Compound Effect. YOu can try Displacemnt Map which is a Compound effect.

Using an Adjustment Layer together with a mask, as you know, is one way of controlling the location of where an effect occurs. But since the effect you applied isn’t a Compound Effect, this method only serves to affect the region where the effct occurs but not its intensity.

There are tutorials here at th COW on Displacemnt Mapping in AE.

Cheers
RoRK

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[Kevin Camp]

you might try displacement map… it will use a second layer to create the distortion. essentially light pixels will cause displacement one way, dark pixels will cause distortion the other. since this effect uses a layer, you can use a mask on that layer to effect what will be distorted….

fractal noise, when the evolutions are animated and as a displacement map, looks a lot like turbulent displace. so you can create a precomp with fractal noise on a layer, then use a mask to select the areas you want to distort. bring that precomp into your other comp, apply displacement map on the layer you want to disort (or as an adjustment layer), use the noise comp as the displacement layer.

you should be able to get what you are looking for, unfortunately it will tak a bit tweaking and going back and forth between the 2 comps to get it right, and the effect will render much slower than turbulent displace.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW

[Darby Edelen]

As an addendum to Kevin’s post. 50% Gray areas in the selected channel will not be distorted at all.

Optionally you can use different channels (the default is the red and green channels) for horizontal and vertical displacement to get more interesting results.

Darby Edelen

[Ian Brenneman]

Hello,

Thanks for replies! I’ll give displacement map a try again. I’ve used it quite a bit but never thought to use it with an adjustment layer. I often found that it only seems to bend in one direction but perhaps I just need to play with the displacement source images some more. 🙂

Aside from turbulent displace, what about things like Gaussian/Fast Blurs. Are these also compound effects?

thanks again!
Ian

[Kevin Camp]

[Ian Brenneman] “Aside from turbulent displace, what about things like Gaussian/Fast Blurs. Are these also compound effects?”

did you mean displacement map, rather than turbulent displace… displacement map is a compound effect…

as far as the blurs go, compound blur, lens blur and cc vector blur are compound effects. compound blur will use another layer to effect how much blur to apply to areas. lens blur allows you to set a depth matte to create nice depth of field like blurs, particularly useful with compositing 3d renders. i’ve never found a use for vector blur, but it also allows you to use another layer as a vector map… the other blurs are not compound effects…

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW

[Kirk Tabalotny]

this may help, Ian – can’t remember where I recently found this solution but it is essentially the After Effects version of using a luminance-based layer mask in Photoshop. I just tried it out applying Turb Displacement selectively, and it seems to obey white, black & grey areas of the ‘masking’ layer. Try this:
1. in a new comp, place the video layer that will be receiving the turb. displace effect.
2. create an adjustment layer above the video layer & apply your effect to it (ie turb. displacement)
3. create a black solid & put it above the adjustment layer
4. apply some form of mask to the solid – a gradient, a feather mask, fractal noise, whatever. If desired, use a curves or levels effect next to tweak the appearance of this ‘mask’
5. set the transfer mode of the adjustment layer to “Luma Inverted matte” and woohoo! – turbulent displace is applied selectively to your video layer.
I tried adjusting the curves effect (+ turned this effect on & off) in the ‘mask’ layer to determine whether shades of grey do in fact influence the degree to which the turb displacement effect was applied to my video layer. It seemed to – I used a radial ramp and watched the turb displacement effect shrink & grow as I manipulated the End Position of the Ramp. Everything in the video layer that lay in the zone between Start & End points of the Ramp was affected, which means that grey levels in the mask definitely influence the effect. Try it for yourself & see if this is doing what you need.
And of course, you can then also alter the opacity of the adjustment layer itself to further fine-tune the amount of turb. displacement that reaches your video layer. Keep in mind that you’re using an adjustment layer which will pass the effect to all layers beneath it – if you only want to affect a limited number of layers, you’ll have to quarantine them by precomping them with the ‘mask’ and adjustment layers.