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Video RAM - how much do you really need?

By: Nick Evanson Nov 02, 2007

Oblivion: King of the Draw Distance

Oblivion maybe getting on a wee bit now, but when it comes to drawing things in the distance, it's still king! We picked a location in the game that starts off with lots of vegetation before opening out to show a huge expanse; we also set all of the detail sliders to their maximum (as well as enabling HDR), and then recorded the amount of video RAM used for different resolutions and AA levels. The same runs were then repeated at 1600 x 1200, but this time, the game's built-in detail presets were used. This method of testing was employed for all of the games you'll see in this article, so bare this in mind.

VRAM usage across resolution and AA

VRAM usage across presets

With having to render distant objects and a myriad of detail close up, Oblivion needs to a lot of video memory for all its textures. The use of HDR also adds to this but even at its lowest settings and resolution, it still needs 90MB of video memory but at least things don't get serious until the detail levels are at their highest. How this affects the look of the game can be seen below:

Very Low graphics preset

Low graphics preset

Medium graphics preset

High graphics preset

Ultra High graphics preset

With the best possible visuals enabled, the rendering engine is using hundreds of textures (some small, some huge), as well as additional frames for the post-processing effects. All of these require lots of memory, which is why the Ultra High preset, at 1600 x 1200 with no anti-aliasing, consumes nearly 250MB in total. The biggest crunch for this game is when anti-aliasing is applied: more RAM is used at 1024 x 768 with 4x AA than at 1600 x 1200 with no AA. Only the very latest generation of graphics cards can apply true 8x multisample anti-aliasing and whilst the performance hit from using this will vary from game to game, the memory requirements are something else. Just taking the maximum resolution figures, 8x AA needs an additional 370MB by itself - clearly if one had a 256MB graphics card, no matter how fast it was, one couldn't really use this level of anti-aliasing because none of the textures (or AA buffers, for that matter) would fit into the onboard RAM!

Gamers typically either use 4x anti-aliasing or none at all, so for the rest of this article we shall only examine these two settings. However, Oblivion isn't the only game to use big draw distances with lots of textures, so let's look at another example.