Trapcode Form

Visibility Group

The Visibility group establishes a range where particles are visible. Distances are defined by how close or far away the particles are from the camera. It can be used to fade out distant or near particles. The units for these values are determined by After Effects' camera settings.

At left, the Visibility group. At right, a diagram of how Visibility works in Form.

Far Vanish: The far distance from the camera when particles become completely invisible. Low values mean the particles are farther away and become invisible. High values mean the particles are closer and stay visible.

Left to right, Far Vanish set low and high.

Far Start Fade: The far distance from the camera when particles start to fade out. Low values make the fade apply itself. High values keep the fade from happening.

Left to right, Far Start Fade set low and high.

Near Start Fade: The near distance from the camera when particles start to fade out. Low values keep the fade from happening. High values make the fade apply itself. (The opposite of the Far Start Fade parameter.)

Left to right, Near Start Fade set low and high.

Near Vanish: The near distance from the camera when particles become completely invisible. Low values mean the particles are closer and stay visible. High values mean the particles are farther away and become invisible. (The opposite of the Far Vanish parameter.)

Left to right, Near Vanish set low and high.

Near and Far Curves: The curve used to fade particles in the Near and Far Fade zones. The curve can be Linear or Smooth interpolation. With Smooth, the visibility for the form will fade less gradually than with the Linear option.

Z Buffer : Z Buffer lets you select a 2D, comp-sized, lightness-based, linear layer to use as a Z-buffer. A Z-buffer contains per-pixel depth values. Typically, Z-buffering stores the Z-axis value of each pixel. This holds information about the distance from the camera viewpoint for each pixel.
Z-buffering can be useful when particles are to be inserted into a scene from a 3D application (like Cinema 4D). The 3D app can be configured to output a Z Buffer. (This is also known as Depth Map or Depth Buffer.)
If the Z Buffer is not anti-aliased leaving it a bit rough on the object edges, it often won’t matter if the particles are small and moving quickly.

Z at Black Control: what depth (distance to camera) a completely black pixel in the Z Buffer means.

Z at White Control: what depth (distance to camera) a completely white pixel in the Z Buffer means.

Obscuration Layer: Since Trapcode Particular is applied to a 2D layer and the particles live in their own 3D world, other layers in the composition won't automatically obscure the particles. The Obscuration Layer provides a way to insert a 3D layer into the particles' world.

Any 3D layer in the comp can be used to obscure particles. To do this, place the Obscuration Layer below the particle layer in the Timeline. Make sure its 3D switch is checked in the Timeline. Then select that layer in the Obscuration popup.

Technical notes:

• The Obscuration Layer must have 'Continuous Rasterize' switched off in the Timeline layer switches.
• The Obscuration Layer must have '3D' enabled in the Timeline layer switches.
• Obscuration does not work with semi-transparent layers.
• This obscuration is not anti-aliased so its effect can look a bit rough on the layer edges. In many cases, this issue doesn't matter because particles are small and move fast.

Left to right, before and after Obscuration Layer is enabled.