Game Development Reference
Figure 4.47 The beautiful baby.
When I blur this image with Fast Blur, the edges become
blurred and transparent, showing through to the layers beneath.
Fig. 4.48 shows the result of blurring the beautiful baby image
with the Fast Blur effect. I placed a checkerboard pattern behind
the image so you can see where the transparency is created.
If we select the Repeat Edge Pixels option, the pixels on the
edge will be allowed to be blurry but not transparent. This option
lets us have our cake and eat it, too (Fig. 4.49).