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Activity Forums Adobe After Effects Expressions expression for light intensity

• # expression for light intensity

Posted by on May 3, 2005 at 2:29 pm

so i hve ten layers in 3d space. they are stacked upon each other and then pinwheel/gatefold open, then rotate, so that i end up with a circular “wall” of these pics. i then have a light mapped to each of these pics. end result is exactly what i want. problem is at the beginning. all the pics start at the same position, so therefore i have ten lights all shining on the same spot. a bit bright. what i was thinking i could do was map the intensity of the light to the rotation value of its target layer. i tried that with just a pickwhip expression, but my rotation values start negative end at various values. how would the expression look to make the light intensity go from 0% to 100%, but the rate would be relative to the rotation?

is this making sense?

thanks,
mike

3 Members · 5 Replies
• 5 Replies
• ### Mylenium

May 3, 2005 at 6:20 pm

Assuming your rotationY is from 0-360 degrees and driving your lights, your expression could look like that:

[linear(thisComp.layer(“image”).rotationY,0,360,0,100]

The last two numbers are the intensity. Adjust everything as needed.

Mylenium

[Pour Myl

• ### Michael Johnson

May 3, 2005 at 6:45 pm

excellent! i’ve been spending all day learning how expressions actually work (versus just using the pickwhip). man is there alot!!!!

thanks

• ### Michael Johnson

May 3, 2005 at 7:16 pm

hmmm… having a bit of trouble with it. i was getting errors with yours, expecting this or that. also, my rotation actually goes from -36 to 0.

here’s what i have rigt now:
thisComp.layer(“Null 2”.rotationY

I don’t get error, but the intensity of my light goes from -36 to 0 percent.

where am i going wrong?

• ### Mylenium

May 4, 2005 at 5:00 am

Just forgot the closing bracket on my original expression. Here’s one that should work for you

[linear(thisComp.layer(“Null 2”).rotationY,-36,0,0,100)]

Mylenium

[Pour Myl

• ### Skacey

May 4, 2005 at 5:01 am

multiply your result by -3 and subtract it from 100 – so you have

x = 100 – (y * -3)

where x is your intensity and y is your rotation

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