I came across this amazing piece of tweak for Crysis, solely for Windows XP gamers.
Here is one of the screenshot taken from here. Click the picture to enlarge.
The first screenshot is the DirectX 9 effect screenshot, while the second one is the DirectX 10 effect screenshot.
You can download the patch from FileFront.
Or you can just add this string of command to the end of the the game shortcut:
+r_sunshafts 1 +e_water_ocean_fft 1 +g_battleDust_enable 1 +r_WaterGodRays 1 +r_UsePOM 1
Go try it out and express your joy here!
