https://bugs.freedesktop.org/show_bug.cgi?id=36602
--- Comment #20 from Andy Furniss lists@andyfurniss.entadsl.com 2011-08-05 12:29:10 PDT --- Created an attachment (id=49972) --> (https://bugs.freedesktop.org/attachment.cgi?id=49972) cubemap demo showing Hiz corruption.
Other demos seem to have only the diagonal affected not the bottom like this one.