Does anybody have an idea how transitions are done? o.o; My guess would be simple multi pass multitexturing using the transition files as alpha maps. How does he vague parameter control the transitioning?
And here I was thinking Blizzard knew it all. :V
I was always curious myself.
After a bit of research it seems that Enterbrain was pretty lazy on that, too. DirectX seems to support some exotic blending modes with the alpha channel of the second texture and min/max caps for that alpha. Basically they shift the min/max values where the vague parameter seems to be the difference between min and max. That's good because we can be lazy as well (especially since we don't have to implement that kind of blending manually).
http://msdn.microsoft.com/en-us/library/bb172508(v=vs.85).aspx
The blending mode they used should be one of the ones in the second half (the alpha ones). I'll try experimenting with it and see who things turn out.
EDIT: Or not. ._. I have to look further into this.
here's some information on transitions http://www.allegro.cc/forums/thread/591493
Those are just manual implementations of some fading sequences, this doesn't really help. I am looking for a crossfade effect where an image is used as progressive alpha channel transition control for the destination image. I mean, I can implement it myself, that's not an issue. But that would be horribly slow and unnecessary. RMXP most probably does it through some simple multitexture effect or alpha cap and I'll figure out something with DirectX to copy that effect.