This game uses Dunia Engine, the same that Far Cry 2 uses. However, I can't remember if you have access to the console in Avatar. If you do, try some of these commands:
Evict_Resources - Seems to clear any cached resources by the game, the "?" command says "D3D and driver-managed" so perhaps it's for graphic data.
Gfx_Bloom - Disables (Or enables, it's a 0 - 1 or on/off command.) the "bloom" effect, gameworld looks a bit softer and brighter with it enabled.
Gfx_ClusterLODScale - Primarily seems to control grass density, higher values makes the grass sparser with low values (down to 0) tightening grass.
Gfx_DetailDistanceScaleModifier - Can't see any differences in the editor, needs to be tested better in the actual game.
Gfx_DisableShadowGeneration - Does what it says and disables (1) or enables (0) shadows.
Gfx_Hdr - Also a on/off (1 or 0) command which disables or enables the high dynamic range lighting effect.
Gfx_HemiQuality - Seems to relate to ambient shadows or shadows on objects 0 disables it and 1 uses a lower quality effect while 2 uses a high quality.
Gfx_KillLODScale - Controls the LOD (Level of detail) distance for objects, higher values decreases it and lower values increases the LOD, 0 disables LOD.
Gfx_LeavesRatio - Controls the amount of leaves on vegetation such as trees goes from 0 (Very few leaves) to 1 (Full leaf quality.)
Gfx_LeavesShadowRatio - Controls the amount of shadows from vegetation with 0 disabling it and 1 enabling full shadows.
Gfx_LODScale - Similar to the KillLodScale command but for objects near the player, goes from 0 (Disabled LOD system) to 12 (Lowest LOD quality.)
Gfx_MaxDecalCount - Maximum amount of decals before old ones are replaced (Seems to go from 0 to 9999)
Gfx_MaxDecalCountPerType - Similar to the above but limits for similar decals like knife slashes at wood or bullet decals on metal.
(Increasing both doesn't seem to help with decal life time such as bullet wounds, decals are still removed very quickly.)
Gfx_MaxFPS - Limits the maximum FPS (Frames per second) or framerate the game uses (I.e if using Vsynch at 60Hz this can also be limited to 60.)
Gfx_MaxHemiMapDistance - Draw distance for the hemisphere map (Probably related to the above hemisphere quality command.)
Gfx_RealTreeCapsMaxDistance - Unsure but might be related to the tree system.
Gfx_RealTreesLODScale - Similar to the above command but for LOD quality.
(Can't see any differences with adjusting these two, need to test it better in the actual game.)
Gfx_Showconfig - Shows the current configuration (Shows the settings you use in the console window.)
Gfx_SunShadowRange0 (There's also SunShadowRange1 and SunShadowRange2) - Might be related to shadow distance.
(Needs to be tested in the game.)
Gfx_TerrainDetailBlendViewDistance - Might be related to the view distance where different textures meet are seamlessly blended together.
Gfx_TerrainDetailViewDistance - Migtht be related to the above, perhaps they're used for the view distance of detail textures.
(Overlays that add more depth and "detail" to the actual textures, needs to be tested in the game.)
Gfx_TerrainLODScale - Might be the LOD distance for the actual terrain. (Doesn't do much if LOD distance itself is disabled or set very low.)
Gfx_WaterReflectionQuality - Controls the water quality with low values (0 - 1) having no or basic reflections and successive values increase it.
Gfx_WaterRefraction - Causes water to refract or distort when hit with objects or walked in (Either 0 to disable or 1 to enable).
Exec - Executes a file containing various parameters like the above ones, useful as this helps from having to type them every time game is started.
(Such as placing a Config.txt file in the install directory and using "Exec Config.txt" to load it instead of typing each individual command.)