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Planar Fog in After Effects

Background Color with a purpose By Stephen Schleicher
Great strides have occurred over the last couple of years by bringing many 3D concepts and tools into this once 2D compositing program. While the current version of After Effects supports 3D ?fog (z-depth information) from third party programs (LightWave, 3dsmax, Mays, etc.), there isnt a built in fog-filter. Or is there? In this After Effects 6.0 exercise, well use the basic Tint effect, expressions, and the Background Color of the Comp to create a unique Planar Fog effect.

Way back in the early days of my 3D experience, I used NewTeks LightWave 3D quite a bit (back then it was still part of the Video Toaster and ran on an Amiga). In order to simulate fog, LightWave would take the color of the background and tint the objects in the scene based on their distance from the camera. You could set the minimum and maximum distance of this fog to achieve varying densities. Of course the greatest problem with this effect was that you didnt have swirling fog, you couldnt have ground fog, and the results were less than stellar. However there is one big advantage to using this type of fog effect if you want to recreate the haze that is present in our atmosphere (atmospheric volumetrics).

You have seen this effect in mountain range photos (or in real life) where the range that is further away takes on the color and contrast of the atmosphere. DaVinci noticed this and wrote about it. Ancient Asian art shows this, and today, we can bring this same effect to After Effects.

Since this effect is most noticeable in landscape images, lets create a landscape composition and create the effect from the ground up. In order to fully understand what we are going to do, we need to define what controls we want over the effect.
  • The fog color should be the same as the Background Color of the Composition

  • Since layers will move in and out of the fog and change color and contrast as they move closer and further from the camera, we need to measure the distance from the layer to the camera and tint the layer accordingly.

  • We need to set minimum and maximum distances for the fog. This will determine how far the camera will see a layer before it is totally enveloped by the atmospheric effect.

  • Need to be able to save this as a favorite for easy application on other layers.

Setting the scene
Lets begin by setting up our scene.

Step 1: Create three solid layers (Command+Y) and give them a nice green color.

Step 2: Using the Pen Tool create a mountain range mask for each of the layers.

Step 3: Make each of these layers a 3D layer and position them along the Z axis.

Step 4: Set the Background Color for the Comp to a light blue.

Step 5: Add a Camera to the Composition and place it at the bottom of the Timeline Stack. In this exercise, I used a default 50mm lens with DOF (Depth of Field) turned off.

Ok, our scene is set up, but because each of the layers is the same color the scene looks rather dull and frankly- messed up.

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Related Keywords:fog, planar fog, after effects, schleicher, tint, expressions, adobe

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