Hi,
if i use the gemhead with -1 [gemhead-1] then [gemhead -2] the gemhead -2 is a background? i can work with alpha... but.. i want work like a layer...
No it is not a 'background', if you want to work with backgrounds, you have to displace your object using [translateXYZ] for example... [gemhead -2] is simply render after [gemhead -1] so because of that [gemhead -2] could be transparent (apply some alpha effect) over [gemhead -1] but not the inverse...
for more help have a look at [gemhead] help, all you want to know is explained.
p.