I would have imagined that when an OBJ and a BG have the same
priority value, the OBJ would always be displayed above the BG. In my
GBA/PC environment I deal with it in this way, but not having the
proper SDK+Hardware, I have no way to be 100% sure. As for multiple
sources in an Alpha blend, I deal with it as follows:

BG1 = Priority value 1 (Terrain)
OBJs = Priority value 1 (Game characters, displayed above
terrain)
BG0 = Priority value 0 (Clouds)


Alpha Blend 1st target sources = BG0
Alpha Blend 2nd target sources = BG1 & OBJs

My environment would display the clouds as semitransparent above the
Game characters and the Terrain. (This may or may not be correct, I
may never know!).

Furthermore, let's say I had a third BG (BG2) of priority value 2
(underlying the Terrain) and the Terrain BG contained transparent
sections. If I also had BG2 flagged as an Alpha Blend 2nd source,
then my environment would show the clouds semitransparent over the
BG2 through the transparent sections of Terrain. This sounds logical
(Why else would you be able to flag multiple sources at once?). Does
this sound logical to anybody else??

Just my one shillings worth.

Niall
A bloke from Ireland




--- In gbadev@y..., groepaz <groepaz@g...> wrote:
> Hello fmoraes,
>
> Monday, April 30, 2001, 10:06:33 PM, you wrote:
>
> fnrc> 1. who has the highest priority in the end? OBJ or BG? I
mean, OBJ
> fnrc> priority 0 and background priority 0?
>
> backdrop -> obj -> bg (highest)
>
> fnrc> 2. with alpha blending, how does it work if you have more
than one
> fnrc> target surface? What if the first surface is transparent?
>
> objs blend only to the bg, not other sprites ... no, it doesnt quite
> look like what you would expect ;/
>
> --
> Best regards,
> groepaz mailto:groepaz@g...