COMPO JOINT HELL

[Sorlag]

Hi!
I'm trying since now a while to obtain, with CALLISTO, a glass object with a coloured mark on.
In this aim, as told in the manual, I'm using COMPO JOINT that way :
[CALLISTO COMPO JOINT]
>[glass object]----------->Glass surface
>[CALLISTO COMPO JOINT]--------->B&W Mask (on diffus / Normal)
>>[CALLISTO COMPO JOINT]--------> Color picture (on diffus / Normal)

And it only works toward the mask, the engine works as if the colored picture was not supported : I have the glass, but with a black mark, with no gradiant due to the lightning.

Little précision : I tryed the same process, but modifying the little planets located in ShadeExplorer - Simple spheres mapped with COMPO JOINTs. I only replaced their map by mines and - surprise - it works, my mark appears with its good colors...

Did anyone ever met this problem and have a solution for me? or should I contact an exorcist?