Applying an effect or opacity<1 to a Group or CustomNode will cause their children to be rendered into an image prior to applying the effect or blending operation. If any of the children has a 3D transform, the rendered image will lose all 3D information. There may be alternative semantics we can use for opacity, but effects are inherently 2D, image-based operations.

There are two main consequences of this issue:

1) The transformed shapes in the graph will be rendered as it if they were 2D, since they must be projected into a 2D plane in order to render them into an image.

2) We will lose any depth information needed for Z-buffering

Note that applying an effect or opacity<1 on a leaf node will not have this issue.

At a minimum we need to:

A) document the rendering semantic of effect on Group/CustomNode
B) document the rendering semantic of opacity on Group/CustomNode