The Depth Matte effect reads the depth information in a 3D image and slices the image anywhere along the z axis. For example, you can remove a background in a 3D scene, or you can insert objects into a 3D scene.

To insert a layer into a 3D scene, apply the Depth Matte effect to the layer containing the 3D scene, set the Depth property to the depth at which you want to insert the new layer, duplicate the 3D scene layer, select Invert for the 3D scene layer on top, and place the new layer between the two 3D scene layers in the layer stacking order in the Timeline panel.

This effect works with 8-bpc color.

Original (top left), with effect applied (bottom left), and with effect applied and Invert Alpha selected (bottom right)

Depth

The z axis value at which to slice the image. Everything with a depth value less than this Depth value is matted out.

To determine the depth of an object, click it in the Composition panel or Layer panel using the Selection tool while the effect is selected.

Feather

The amount of feather along the matte’s edges.

Invert

Select to matte out everything with a depth greater than the Depth value. Deselect to matte out everything with a depth less than the Depth value.