fixed: enable post processing on fbo to get mip maps        add comment explaining this
fixed: enable post processing on fbo to get mip maps
       add comment explaining this

git-svn-id: 6c7e10cdde2c115f53707ba8ec4efe535f92d362@1983 4683daeb-ad0f-0410-a623-93161e962ae5

jondo2010/OpenSG,jondo2010/OpenSG,jondo2010/OpenSG,jondo2010/OpenSG,jondo2010/OpenSG