This post is meant to describe the graphics settings of Alan Wake in some detail, and tell how they affect performance.
RESOLUTION - Resolution can be adjusted freely based on what your graphics card / monitor tells our game it can do. The game supports different aspect ratios too. Increasing resolution is fairly GPU-heavy as the game also increases the resolution of many of the internal rendering buffers.
Alan Wake needs a minimum 1024x768 resolution to run. When you first run the game, it tries to run in your desktop resolution unless you have a very slow system (there is a very light-weight automatic performance detection on the first run).
If you have low performance we recommend you run the game at 1280x720 or 1024x768.
VSYNC - You can enable or disable the vertical sync. Disabling it causes the game to render "as fast as it can" meaning your frame rate may go up, but also will cause the game to "tear (http://en.wikipedia.org/wiki/Screen_tearing)" and the frame rate to feel more uneven.
GRAPHICS QUALITY - Low, Medium, High or Custom. A few pre-defined settings for different performance levels.
ANTIALIASING - 2x, 4x, 8x - defines the full screen MSAA level. 8x is pretty expensive for the GPU. Best performance & visual compromise is 4x setting and FXAA set to high. Antialiasing can't be disabled in Alan Wake, as the engine has been designed so that AA is on at all times. If you disable it from e.g. driver's control panel, the game will likely work but you will see visual artifacts.
FXAA - Off, Low, High. FXAA is a complementary post-processing anti-alias technique. It's not really expensive, but should be turned off on low-end systems. High uses a slightly slower, better quality technique.
ANISOTROPIC FILTERING - Off, 2x, 4x, 8x, 16x - sets the texture filter mode. Makes the textures look sharper/nicer.
SHADOW QUALITY - Low, Medium, High. Low is meant for older, low end systems. This setting really affects CPU and GPU performance. Low renders one shadow region less and the shadow draw distance is small. Medium corresponds approximately to what the Xbox360 build does, and high has increased resolution and filtering.
SSAO Quality - Off, Low, High - Screen Space Ambient Occlusion is a post-processing effect that makes objects look like they fit better in the scene by shadowing the edges. Needs purely GPU power. High uses better quality effect and takes quite a lot of power, Low can look a bit noisy at times.
BACKDROP QUALITY - Low, Medium, High - affects the rendering quality of the game world's backdrop beyond draw distance (see below). A good compromise on a medium PC may be lowering draw distance but keeping this setting at medium or high, as the performance effect is not huge, but the Low quality backdrop can look a bit blocky.
GODRAY QUALITY - Off, High. God Rays from the sun are on only during daytime scenes. On a low end graphics card this can take a lot of performance for little visual benefit - it's a cool but rather subtle effect. This setting has no effect on performance or visuals during night time.
VOLUMETRIC LIGHT QUALITY - Low, High. Filtering and resolution of the Volumetric light effects in the game. This is a night time setting only. High makes lights look really pretty and is not massively expensive for the GPU to render.
DRAW DISTANCE - Slider that affects the landscape and object draw distance. It also affects the landscape tessellation distance which is a CPU intensive process. Minimum is 650m, max is 1500m during daytime and 1000m during night time. This slider has a large effect on CPU power in the game, but also affects GPU performance. Recommend turning to minimum for low end systems.
LOD DISTANCE - Slider that changes the distance when objects change from lower level of detail models to the high detail models. It also affects how far small objects are rendered. This can have a rather big impact on performance, both CPU and GPU power. Recommend turning to low on slow systems.
FOV (under control options) - Slider that affects the FOV factor compared to the default FOV. The FOV in the game is affected by aspect ratio as well as many in-game events (sprinting, boosting), thus this has to be a multiplier rather than a fixed angle setting. Our default FOV in 16:9 is about 80 degrees. Increasing the FOV requires more processing power both from the CPU and GPU - a larger area with possibly more visible objects is rendered.
That's it! Hope this is helpful.