S.T.A.L.K.E.R.: Clear Sky

Publisher: Deep Silver

S.T.A.L.K.E.R.: Clear Sky is the prequel to GSC Game World's sleeper hit S.T.A.L.K.E.R.: Shadow of Chernobyl and was unfortunately released in a bizarrely unfinished state and it's taken some time for the game to reach the levels of stability that we expect from a game. However, with the new 1.5.07 patch, Clear Sky runs great and as you would expect it to.

Clear Sky uses a heavily tweaked version of the X-Ray engine, which debuted with Shadow of Chernobyl and was updated to support several new graphical effects using DirectX 10 (and later DirectX 10.1 through the 1.5.06 patch). The improvements include enhanced visual effects like 'God Rays', wet surfaces, volumetric light and smoke, depth of field blurring, and screen space ambient occlusion lighting as well as better textures.

We used a custom timedemo for our testing, which incorporates many of the advanced effects introduced with DirectX 10 – we also enabled DirectX 10.1 on the Radeons. However, due to the intensity of engine, we have set the in game details to "High" instead of "Maximum" and have left anti-aliasing disabled for the time being.





There's very little between the Radeon HD 4870 1GB and GeForce GTX 260+ 896MB graphics cards at 1,680 x 1,050 - the only resolution to really deliver anything near to playable frame rates. The Radeon has the edge, but it's by less than two percent, which makes the difference almost negligible in a real-world scenario.

Where the difference comes to light though is with dual-GPU configurations – CrossFire has nearly a seven percent performance advantage at this resolution and is able to maintain playable frame rates right the way up to 2,560 x 1,600 unlike the GeForce GTX 260+ SLI setup, which falls a little short at the highest resolution.

It's no surprise that the GTX 280 is the fastest single GPU card and that the Radeon HD 4870 X2 is miles ahead of it in this title. What is interesting though is that the Radeon HD 4870 512MB card drops behind the 1GB version even at 1,680 x 1,050 where the former struggles to deliver smooth and playable frame rates.