Blend text in "karaoke style"

hello !
I’m trying to make text animation in karaoke style.
everything is fine until I put a white background-
see the patch which explains my problem…
with no background:

with white background:

how could I add white background and preserve my text blending wipe effect ?
thanks in advance.


blend_text_debug.v4p (21.7 kB)

My fast solution. (3.5 kB)

@h99 in your file the white is not shown at all…

i fear that understanding the blend function is not so trivial. so here i made comments in the patch to explain what happens to the pixel buffer when you blend the different layers into it.

the trick is to start with a pixel buffer with all alpha set to 0. then let the text write something into the alpha channel and use that to blend the other two quads:

blend_text_debug (1).v4p (38.0 kB)

tonfilm you are the boss !
always got lucky with alpha blending so far without knowing what I was exactly doing…so thanks a lot for your greats explanations !!!

@tonfilm This is not the first time I misread something, nor the last.