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- Date:
- Wednesday, October 01, 2008
- Author:
- Mark Warner
- Editor:
- Brent Justice
- Google +1
S.T.A.L.K.E.R.: Clear Sky - Gameplay Perf and IQ
S.T.A.L.K.E.R.: Clear Sky has arrived to give us our apocalyptic fix, and just maybe grind our video cards into dust in the process. We'll find out how AMD’s and NVIDIA's latest high-end GPUs handle this graphically demanding new game!
Performance - Highest Playable
S.T.A.L.K.E.R.: Clear Sky has a fairly wide range of gameplay environments. The overriding theme is chaos and decay, so everything looks aged, broken, and dirty. There are crumbling buildings, shattered vehicles, and warped and twisted trees dotting the landscape. There are seamless interior and exterior environments, as well as smaller "instanced" environments that exist somewhat outside the regular game world. For example, the Clear Sky camp itself seems detached from the rest of the world.
For our gameplay performance evaluation, we chose a route through the labyrinthine swamps surrounding the Clear Sky camp. During the test, we experience outdoor areas, indoor areas, dense brush, combat and even the progression of time from late afternoon to the failing light of evening. The route lasts about 10 minutes and takes us through a wide circuit around the swamp.
Graphics Options
Clear Sky has a graphics option panel very similar to 2007's S.T.A.L.K.E.R.: Shadow of Chernobyl. This is not surprising in light of the fact that Clear Sky shares a graphics engine with Shadow of Chernobyl. But while it is the same underlying engine, it has definitely been updated to take advantage of the advanced power afforded by modern video cards.
There are two new rendering modes, for a total of five. The first Renderer "Static Lighting" essentially reverts Clear Sky into a DX8 compatibility mode. The second option "Object Dynamic Lighting” enables dynamic lighting on some objects, cast by the player's flashlight. Next is "Full Dynamic Lighting," which is the full DX9 dynamic lighting model that was the maximum setting in Shadow of Chernobyl. The first new renderer is "Enhanced Full Dynamic Lighting," a DX9 mode which enables some of the new effects like Sun Rays and Volumetric Light. The top option is "Enhanced Full Dynamic Lighting (DX10)," abbreviated "Enh. Full Dyn. Lighting" in the game menu, which adds some new DX10 effects like Wet Surfaces and Volumetric Smoke.
Selecting an option in the "Quality Settings" drop-down simply applies a preset of graphics options, designed to help novice users get the best performance they can without fiddling with graphics options they may not understand. For our purposes, we will not be using this method of selection.
Clicking on the "Advanced" button on the Video options tab gives us what we are looking for: sliders and buttons! For the tweakers out there, this is where you want to be. There are 24 options total, allowing you comprehensive control over the game's environment. For the most part, the options are named appropriately and they do what you would expect. We will go over a couple of the more enigmatic options here. For a more in-depth analysis of these options, visit Koroush Ghazi's excellent guide at TweakGuides.com.
The first option we want to talk about is the Anti-aliasing slider. The first thing we noticed is that there are way more slider notches than there should be. We would expect notches for 2X , 4X, 8X, 8XQ, 16X, and 16XQ when using NVIDIA cards, and options for 2X, 4X, and 8X when using an AMD video card. However, there are far more than that, and with good reason. In DX9 mode, Clear Sky does not support true multisampling anti-aliasing. Therefore, when in DX9 modes, this option applies a sort of shader-based edge blurring technique that is quite ineffective. In DX10 mode, however, it does seem to enable "real" AA, although your guess is as good as ours as to what AA level each notch actually means.
Next is the SSAO drop-down. SSAO is an acronym which stands for "Screen Space Ambient Occlusion." It is a lighting technique which uses real-time surface occlusion algorithms to enhance the realism of lighting on both dynamic and static objects. Games like Crysis and Age of Conan also use this technique to add depth and realism to players, NPCs, weapons, vehicles, and buildings.
NOTE: The below tables will only reflect settings that were different from video card to video card at each resolution. In all of our testing, we did not have to alter the top slider settings (Object Detail, Texture Detail, etc.), except for the AA slider, which is detailed below. These settings were found to have a minute impact on performance unless the sliders were reduced to or below about the 25% mark, which sometimes had a profound and undesirable effect on the gameplay experience. Therefore, to get our video cards playable at these resolutions, we concerned ourselves mostly with the advanced settings which are shown below. Unless specified in the text below the graphs, settings not shown in the tables can be assumed to be ON or at their maximum values.
Highest Playable Settings at 2560x1600
At 2560x1600, none of these four video cards could handle the DX10 rendering mode, but they all were able to use the "Enhanced Full Dynamic Lighting" mode. Volumetric lighting had to be disabled, and the Sun Quality setting was at "Low" across the board.
At this high resolution, the GeForce GTX 280 and the GeForce GTX 260 gave us the most consistent experience. As you can see from the graphs above, the performance of the two NVIDIA video cards was the most consistent, with no extreme dips or spikes. On the other hand, the AMD video cards were all over the place. They spiked, they fell back down, and it could definitely be felt in-game. We had input lag issues and stuttering issues while walking around the swamp. It was mostly a playable experience, but the gameplay did not feel as refined and smooth as it did on the GeForce video cards.
Both the NVIDIA GeForce GTX 280 and AMD's ATI Radeon HD 4870 X2 came out with the same playable settings at this resolution, albeit with wildly different performance profiles. The Radeon HD 4870 X2 has a tremendous amount of computing horsepower, as witnessed by the very high peaks in performance, but it still suffers from some unfortunate downturns in performance, which kept us from being able to increase the settings to take advantage of that extended power. The GeForce GTX 280 is obviously less endowed, but in our experience, it made more efficient use of its processing power and provided us with a more fluid gameplay experience in S.T.A.L.K.E.R.: Clear Sky.
With the GeForce GTX 260 we had to disable Sun Rays and SSAO to keep framerates from dipping into the low teens and becoming generally unplayable. Using the Radeon HD 4870, we had to go even further and disable Detail Bump mapping, Steep Parallax, Sun Rays and SSAO, Soft Particles and Water, and even Depth of Field. If you have a monitor capable of 2560x1600, the ATI Radeon HD 4870 is not the video card for you playing Clear Sky.
Highest Playable Settings at 1920x1200
At 1920x1200, we still were not able to turn on the DX10 renderer in Clear Sky without sacrificing something more important. So again we kept with the high-end DX9 rendering path, "Enhanced Full Dynamic Lighting." Note that every option other than what is chronicled below was set to the maximum available setting.
At 1920x1200, we see a familiar pattern to what we saw at 2560x1600. The GeForce GTX 280 and GTX 260 provided a consistent gameplay experience without a lot of high peaks and low dips in performance.
The ATI Radeon HD 4870 X2 was really stuck between a rock and a hard place at 1920x1200. Performance was generally very good, except for a few downward spikes, so we wanted to increase the settings. Unfortunately, the only option we had was to enable the DX10 renderer, which caused a huge performance drop, which made us disable the DX10-specific features, as well as a few other features that are common to the DX9 rendering path. So we were essentially forced to stay with DX9 at 1920x1200 in order to have a better experience.
We can see here, that feature for feature; the ATI Radeon HD 4870 X2 absolutely destroys the GeForce GTX 280. The two video cards are using exactly the same settings, which incidentally are the highest possible DX9 settings in this game, and the Radeon HD 4870 X2 comes out a whopping 50% faster in the end.
The GeForce GTX 260 and the Radeon HD 4870 were almost neck-and-neck, performance-wise, but the Radeon exhibited some unfortunate fluctuations in framerates. To mitigate the effect of those drops, we turned the Sun Quality setting to "Low" on the Radeon HD 4870. That reduced the extremity of the downward drops and also eliminated almost all of the input lag.
Highest Playable Settings at 1680x1050
Finally, at 1680x1050, we were able to use DX10 on the Radeon HD 4870 X2 without too severe a performance impact. We did have to disable some features, but not as many as we would have at 1920x1200, and we felt that the sacrifices we made were relatively minor compared to the advantages brought by the DX10 renderer. Note that every setting not represented here was at the highest value, except for the AA setting on the Radeon HD 4870 X2. It was disabled to keep framerates out of the basement. The other video cards all used the DX9 renderer, which employs a shader-based fake AA which, to our eyes, doesn't make any difference at all.
At first look, it appears that the Radeon HD 4870 X2 has some headroom here to enable some higher settings, but that was unfortunately not the case. As we can see at the beginning of the test, and again at around the 6 minute mark when we entered combat, framerates dropped back down for an extended period of time and more closely matched what the other video cards were doing. The settings we choose are for the worst case scenario. When we ran with higher settings while we were walking around the world, we found ourselves in real trouble once we hit combat and our framerates went to the floor, preventing us from being able to fight effectively and getting us killed.
Again, the GeForce GTX 280 and GTX 260 gave us the smoothest experience with the least fluctuation in frame rates. The Radeon HD 4870 came close, and was much more stable at this resolution, but you can still see some annoying drops into the teens and lower.