Apple Motion 5.1.1 - Manual (Page 243)

Chapter 7 Basic compositing 243
When working in a 3D group, changes in depth order affect the Stencil and Silhouette blend
modes differently. For example, if you have two layers in a 3D group and the upper layer is set to
Stencil Alpha or Stencil Luma, the blend mode remains in effect when the upper layer is moved
behind the lower layer in Z space. If you have two layers in a 3D group and the upper layer is
set to Silhouette Alpha or Silhouette Luma, the blend mode does not remain in effect when the
upper layer is moved behind the lower layer in Z space.
When you use the Stencil or Silhouette blend modes in a group set to the Pass Through blend
mode, the resulting effect carries down through every layer in every group that lies underneath it
in the Layers list, unless the group that contains it is rasterized. This is a powerful, but not always
desired effect, because it prevents you from placing a background group to fill the transparent
area. You can limit the Stencil or Silhouette blend mode to affect only those layers in the same
enclosing group by setting the group’s blend mode to anything other than Pass Through. For
example, if you set the enclosing group of the two layers in the Silhouette Alpha example to
Normal, then add a group underneath containing additional layers, those layers show through
the transparent areas created by the silhouetted group.
Mask-Affecting Modes
The following blend modes modify the alpha channel of the layer to which the blend mode
is applied.
•
Stencil Alpha: Uses the alpha channel of the affected layer to crop out all non-overlapping
parts of layers and groups underneath it in the Layers list.
Object used for stencil Result Object underneath
•
Stencil Luma: Does the same thing as the Stencil Alpha blend mode, but uses the affected
layer’s luma value to define transparency. Stencil Luma is useful if the layer you want to use for
cropping has no alpha channel of its own.
67% resize factor