You can use the \clip override to define what part of your text shows (or doesn't show).
Then use \t(\clip()) to move the \clip for the wipe effect.
Example: {\clip(0,0,100,100)}{\t(\clip(100,0,100,100))} will wipe the text off the screen from left to right
or {\clip(0,0,0,100)}{\t(\clip(0,0,100,100))}
text to wipe text onto the screen from left to right
(I think I have the parentheses all matched up
)
edit: snippet from MorphineX's guide:
Spoiler:
1) -- Hikari no Kiseki: Pita-Ten Episode 04 Opening --
Features:
1) Line changes to a lighter color to create a feel of fade away.
2) Line fades away "word by word" from left to right instead of the whole thing fades away at once.
How it is done:
1) Via {\t(<t1>,<t2>,\1c&H????&)} from the original style/color
2) Via multiple {\t(<t1>,<t2>,\clip(<x1>,<y1>,<x2>,<y2>)} for each line. The box shrinks after each segment is deleted, since the words within the box are preserved, if the box shrinks from the left to the right, the appearance of fading from left to right is created.
Done First By: Jasconius (Before 5/07/2002)