The rendered output is combined with the background using the normal
painting operation (i.e. the Porter and Duff over operator). This mode is
used to simulate geometry such as guaze cloth or animal fur.
mask
mask: = "mask"
The rendered output is either fully opaque or fully transparent depending
on the alpha value and the specified alpha cutoff value. This mode is used
to simulate geometry such as tree leaves or wire fences.
opaque
opaque: = "opaque"
The rendered output is fully opaque and any alpha value is ignored.
The rendered output is combined with the background using the normal painting operation (i.e. the Porter and Duff over operator). This mode is used to simulate geometry such as guaze cloth or animal fur.