A guide-in-progress to modding Oblivion for mysterious ambiance, visual diversity, and the sense of a larger world.
Part One: Fogging Things Up
Wherein the subject is reduced outdoor range of viewing, a major contributing factor to the sense of the size of Cyrodiil.
Option 1: http://www.tesnexus.com/downloads/file.php?id=18305.
If I were to choose a single mod that does more toward achieving the goal of this guide than any other, it would be All Natural - when set up correctly, of course. Though this is primarily a weather mod (and, in my opinion, the best one currently available), it's of interest in this guide because it has an ini file which contains a fog control segment. It allows you to set variable fog ranges by weather type. It can also control how dark your nights are, make moonlight brighten the night based on moon phase, and change the colors and color saturation of your daylight in various weathers. Editing the ini file for this mod is extremely easy with a great deal of built in guidance. Fog values near the very lowest ranges suggested by the comments will nicely limit your viewing range so that anything just beyond the beginning of distant land is fogged out, and you can see only a silhouette.
Turning off distant buildings while using very low fog settings with All Natural will improve performance with this option and is almost unnoticeable. I don't recommend turning off distant trees, but if you need to for performance, using this kind of fog setting limits the annoyance factor as much as anything will. You may also lower some oblivion.ini settings that will increase performance with no visual loss whatsoever if your fog range is low enough. The values you want to lower are "uGridDistantTreeRange=x" and "uGridDistantCount=x" in the [General] section of the .ini. I've set both numbers as low as 10.
Here is a series of screenshots, showing a cloudy day, a cloudy night with a full moon, and one of a foggy morning. All of these were taken with the uGridDistant values above set to 10, and all fog numbers in the All Natural.ini between 0.2 and 0.4. Note: With the overall settings this low, set the "foggy" weather value as high as clear weather (or higher), otherwise when the fog rolls in, you'll see nothing but white. All other settings can be set up in a logical manner based on weather types using the examples the ini comments give.
http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot10.jpg - http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot9.jpg - http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot11.jpg - http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot13.jpg - http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot12.jpg - http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot14.jpg - http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot15.jpg - http://i523.photobucket.com/albums/w360/with_this_hand/Oblivion/ScreenShot16.jpg
Option 2: http://obse.silverlock.org/ (scroll down to find the download links on the list.)
Streamline is a customizable performance mod that can control almost every aspect of Oblivion's visual quality, ostensibly for performance/FPS gains. However, it can be used, through tweaking, to set up a static fog distance. This is compatible with All Natural; the ini for that mod has further infomation. Streamline comes with a good amount of documentation on how to tweak it. To set up a static fog range, you must set the min/max fog range number within Streamline's Streamsight feature to the same number (or very close to it). This method is inferior to All Natural in that it doesn't offer weather-based fog variance.
A recommended mod to use for other features even if you don't use it for fog management, as it offers both convenience and performance gains.
Option 3: Other fog mods
As a general rule, other mods that set a static fog range are not compatible with weather mods, and are not adjustable unless you can edit them yourself in the CS, or if they offer multiple option ESPs. Searth PES or TESnexus for "Fog". Of these, I have used and liked http://www.tesnexus.com/downloads/file.php?id=33424. These can be easier to install and use than the mods above.
Option 4: Distant land off
This is a fairly self-explanatory option. It's also the only effective way I've seen to have a very, very short, Morrowind-like view distance. Set your view distance under Oblivion's video options to less than 100% view distance. If you're going to do this, I recommend setting it to 75% or below, as this will help minimize some of the "pop-in" caused by the complete lack of distant land. Using 99 or 100% view distance with distant land off makes the pop-in effect extremely noticeable and annoying.
Also of note: This method clearly also offers the largest improvement in outdoor performance for those with computers that struggle with distant land. Most people who use this option will in fact probably do it for performance reasons.
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More to come in the guide. In the meantime, the following links are mods that generally contribute to Oblivion gameplay with the theme of limited vision, visual diversity, and the sense of mystery and a larger world. Most will probably feature in an upcoming segment of this guide.
All of the http://www.tesnexus.com/downloads/file.php?id=19370. Particularly with a limited range of vision, the distinctly different landscapes add immensely to the sense of size and variety of landscapes.
http://www.tesnexus.com/downloads/file.php?id=9276 Better grass with more variety.
http://www.tesnexus.com/downloads/file.php?id=23783 Go for the largest trees option, 150% of normal.
http://www.tesnexus.com/downloads/file.php?id=18385 which can be used alone or in combination with one of the following:
http://www.tesnexus.com/downloads/file.php?id=22819 OR
http://www.tesnexus.com/downloads/file.php?id=35099, the latter being recommended.
Recommended reading:
WrinklyNinja's http://www.gamesas.com/index.php?showtopic=960829.
The All Natural Readme, which has a suggested complementary mods list.
I'm still looking for further feedback on both the content and formatting of the guide, as well as further ideas, particularly about ambient lighting tweaks and mods.
The next addition to the guide will be concerning better tree, grass, and shrubbery groundcover, for obscuring your view in the nearer range.
Thanks to those who have contributed so far, and to Far327, who inspired me with his screenshots and some of the discussion that followed (which I was not a part of but happened upon later), found http://www.gamesas.com/index.php?/topic/1164017-moded-oblivion-screenshot-thread-275/page__view__findpost__p__17385937).