CC Light Rays based on layer's alpha

With this preset you can prevent "CC Light Rays" to cause a light spot if it's not over an opaque part of a layer.

After Effects CS3
Lights
Presets (ffx)

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With this preset based on sampleImage() you can choose an "obscuration" layer. Based on it's alpha values the intensity(brightness) of the "CC Light Rays" is automatically controlled.
Including an "AlphaThreshold" for the "obscuration" layer and a "BrightnessMinMax" for the "CC Light Rays".
Simplay apply it to an "Adjustment Layer".

Here is the basic expression, if you need it "clean".

target = thisComp.layer("obscuration"); // name of the "obscuration" layer
x = target.sampleImage(effect("CC Light Rays")("Center"), [3.5,3.5], true, time);
alpha = x[3] * 100;
linear(alpha, 0, 50, 0, 100);

Otherwise get the preset and you're done ;)

Effects & Plugins

CC Light Rays, Slider & Point Controls

Keywords

sampleImage obscuration expression preset ffx

(Min. Version: After Effects CS3, Category: Lights, Type: Presets (ffx))

posted by mmo on Feb 24, 2009

Modulate the intensity of Lens Flare based on an obscuration layer

With this preset you can cause the opacity of a layer to control the brightness of a "Lens Flare".

After Effects CS3
Lights
Presets (ffx)

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posted by mmo on Feb 20, 2009

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Ascii animation with sampleImage()

More experimentation with sampleImage().
from http://www.creative-workflow-hacks.com

After Effects CS3
Useful things
Expressions

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posted by mmo on Sep 02, 2008

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Rebel CC

A simple, elegant, telecine-style color-correction tool for coloring or grading your movie.

After Effects 7
Color
Presets (ffx)

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posted by MicGyver on Nov 06, 2008

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CC Light Rays based on layer's alpha

Effects & Plugins

Keywords

Related topics:

Modulate the intensity of Lens Flare based on an obscuration layer

Ascii animation with sampleImage()

Rebel CC