Masking Light

[ElDoggo]

I want a light to only be lit in a mask. When I use the pen tool, it creates a new shape layer, and just fils in red. Screenshots to see. How do I make it where the light is only within a mask? Thanks!

Screen Shot 2018 03 07 at 10 21 03 AM — imgbb.com

[Dave_LaRonde]

To do what you want, you'd have to shine a light through a big-ass solid with a mask cut in it.

[ElDoggo]

I put a solid, put a mask on it, put the light under it, and still nothing

[Dave_LaRonde]

Dude -- think in 3D terms.  the masked solid goes BETWEEN the thing you want to light up and the light itself.  You may have to move things waaay back in z-space to get what you need... and if your solid isn't big enough, you see that right away.  You're using the solid to block the light except where the mask is.

Don't forget to set the solid to "casts shadows"  and the thing you're lighting up to "accepts lights".

[Kevin-Monahan]

El Doggo,

How's it going with this? Did Dave's advice help you? Please let us know.

Thanks,
Kevin

[Mylenium]

You cannot mask 3D lighting directly. You have to pre-compose and mask the result of the lit layer.

Mylenium

[Roland Kahlenberg · Accepted solution]

This may not be what you're looking for but it will provide you another with another creative option - use a Gobo effect in AE. In case you're not sure what a gobo is - Gobo (lighting) - Wikipedia 

Essentially, you need an image with an Alpha Channel. This image is placed in front of either a Spot Light or a Point Light. Cast Shadows for the Lights have to be switched on. Cast Shadows (can be set to "Only" too)and Light Transmission have to be switched on for the Image Layer.

Here's a tutorial from Rick Gerard on the topic.

CreativeCOW