Gimp, or Gump?

Ok so here's the problem; i'm currently running Gentoo Linux on my laptop. I try to run emerge gimp, and i get this error:

checking for gtk-config... /usr/bin/gtk-config
checking for GTK - version >= 0.99.7... yes
checking OpenGL... no
checking Mesa... no
checking Mesa with pthreads... no
configure: error: You need GL or MesaGL libraries

!!! ERROR: x11-libs/gtkglarea-1.2.3-r1 failed.
!!! Function src_compile, Line 25, Exitcode 1
!!! (no error message)


i've tried looking in packages.gentoo.org for Mesa or OpenGL libraries and i've found the "Mesa" package which i've tried to emerge, with no luck....

bash-2.05b# ACCEPT_KEYWORDS="~x86" emerge -f mesa
Calculating dependencies
!!! all ebuilds that could satisfy "mesa" have been masked.
!!! possible candidates are:
- media-libs/mesa-3.5 (masked by: package.mask)

!!! Error calculating dependencies. Please correct.
bash-2.05b# ACCEPT_KEYWORDS="~x86" emerge -f =media-libs/mesa-3.5
Calculating dependencies
!!! all ebuilds that could satisfy "=media-libs/mesa-3.5" have been masked.
!!! possible candidates are:
- media-libs/mesa-3.5 (masked by: package.mask)

!!! Error calculating dependencies. Please correct.


what do i need to do to unmask this so that i can emerge it, and once i get it emerged, will it allow me to finish the gimp emerge?

Thanks in advance.
-Matt
P.S This has been x-posted to the gentoo community, and i only received a bit of obscure advice. Please help :-)