In Fedora 10 RHGB has ben replaced by plymouth which no longer uses an X server. Depending on its configuration plymouth will show an animated solar in default configuration during startup. Depending on your graphic card plymouth might not be able to show this graphical screen and just show a text progress bar during boot process.
To use the much prettier boot animation you need to pass the vga parameter to the kernel:

kernel /vmlinuz-2.6.27.9-159.fc10.i686 ro root=/dev/mapper/luks-a0756b8b-2ad8-4758-8b7f-e8225ae0ced7 rhgb quiet vga=0x31b

Depending on your desired colours and screen resolution you need to apply any of the parameters below: