Post Production

After Effects Classic Course: Light Transmission

Some tips for having the colors from one layer project onto others.

3D Lighting is probably one of the more underused creative tools in Adobe After Effects. It’s not just for lighting complex 3D worlds; it can also be used to add “sexiness” to flat 2D sources such as videos.

One of the more advanced 3D lighting tricks is “light transmission” – using the colors present in one layer to project onto other layers. You may think of this as a stained glass window effect, or the light coming from a virtual video screen or projector being illuminated by other surfaces. 

In After Effects, this feature is somewhat non-intuitively tucked inside the “Shadow” parameter. You have a choice as to whether a layer projects a shadow (projects black, multiplied onto other layers), or projects the colors in that layer using an additive blending mode internally.

The series of classic movies below show how to enable this feature, and how to cure some common problems with it such as getting the sharpness/blurriness blend right, and how to deal with the light illuminating the projecting layer to be restricted to just that layer. The later requires diving into another arcane After Effects 3D lighting trick known as “negative light” where a light’s contribution is actually subtracted from a scene. 

These movies are based on the old Classic rendering engine in After Effects. We’ve not been keeping up with the capabilities of the newer rendering engines, but if they don’t support this trick, then definitely make a feature request to Adobe (and Maxon), as this is a cool trick worth preserving.

Introduction & Overview:

Building a 3D World to Support Light Transmission:

Projecting Video From One Layer Onto Others:

Sharpening & Softening the Projected Image:

Removing “Light Leaks” from Outside the Boundaries of a Layer:

These movies previously appeared on Lynda.com/LinkedIn Learning. They’ve retired this course from their library, so we’re making the movies from it available publicly for free. You can either scan our page on ProVideo Coalition to see the other free movies, or check out the Crish Design channel on YouTube.

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Chris & Trish Meyer founded Crish Design (formerly known as CyberMotion) in the very earliest days of the desktop motion graphics industry. Their design and animation work has appeared on shows and promos for CBS,…