Hi. I've tried to got an alpha channel in my materials, but no way to make it work, than i've found this tut:
http://www.filmtecknarna.se/stefan/bottle/index.html
It works, but, is it the only way to implement alpha in xsi ? It's painfull !!!!
Is this the only way to make alphas live ???? 
Onether question :
When working on layers in materials :
Diffuse channel :
I've layer 1 : a Brick bitmap
I've layer 2 : a Rock bitmap that covers the Brick bitmap
Now the 2nd layer covers completly the first cause it has a 100 opacity.
Now i whant to put the Rock layer (1) over di Brick layer (2), to make it render for first and cover it ?
There's no way to drag and drop layers like in software as Lightwave ?
Have i really to go to the render tree ?
Is there any other way to make this simplier ?
My opinion ( but i'm still a rookie with xsi ) is that the material system is too much pleanty of repetive task and a too much panels... maybe i will get used to, but i think lightwave's system is light year behind xsi's, maybe less configurable or powerfull for " hollywood " setups, but for everyday work, much more better...
But, I'm still loving xsi for a lot of features, so i whant to learn it
Please help me !