User:Kesta/LightingWeathersPostProcessing

This page aims to provide an extensive explanation on what lighting and weathers mods are, how they affect the visuals of the game, and what compatibility issues they can produce.

Cells and Worldspaces

There are two different kinds of "environment" in Skyrim: Cells and Worldspaces. A cell is an interior place, while a worldspace is an exterior. There are a few exceptions, where interiors are actually worldpsaces surrounded by walls and ceiling.

There are many differences:

• Only worldspaces have LOD, and use the Grid-based loading system,
• Only worldspaces have an actual ground. The floor in cells is simply a static mesh.
• Worldspaces use weathers where Cells use Lighting Templates.

The last point is the one of interest in this page.

The also have many commonalities:

• They're "containers" for a lot of references, all of the forms found in this area.
• They're navmeshed (or should be).

Despite being all technically identical, Interiors cells can be categorized into two sub-categories in the context of lighting mods : Dungeons and Interiors, as some mods focus only on dungeons, and others on inhabited places.

Lightbulbs

Ligthtbulbs are invisible objects casting lights in a cell or a worldspace. They have several parameters, such as their radius, color, intensity, flickering parameters (to simulate the irregular lighting of a crackling fire for instance), and whether or not they cast shadows.

Lightbulbs mods aim to provide a realistic lighting by moving/deleting/adding/adjusting lightbulbs and lightsources in the Cell.

Here is a view from the Creation Kit to better illustrate the purpose of such mod :

As you can see, the lightbulb (represented by an ampoule) isn't located exactly where the light should originate (the brassier). This leads to inconsistent lighting. Lightbulbs mods move this kind of lightbulb to a more consistent location.

Aside from moving lightbulbs to a more consistent location, here are some basics of what a lightbulb mod does :

• Add lightbulbs where light sources are present without a lightbulb (this is the case of many candles in Vanilla)
• Remove lightsources that don't have a lightbulb
• Remove a lightbulb and its related lightsource for a better global outcome
• Add a lightsource with its lightbulb for better global outcome
• Adjust lightbulbs parameters such as colors/intensity/flickering
• Remove lightbulbs which aren't assigned to any lightsource.

Engine limitations & Workarounds

Additionally, lightbulbs mods aim to provide a workaround about two engine limitations present in Skyrim :

Limited Shadow Casters

BUG:

Only 4 shadow-casting lights can be visualized at the same time. If more shadow-casting lights are present, one of them will be completely disabled.

The shadow-caster limitation is a common sight when using the mod Alternate Start (ASLAL) with any lightbulb mod: They are tailored to have only 4 show-casting lightsources in the beginning cell, but ASLAL add an additional one near the Mara statue.

Lit meshes partitions

BUG:

A mesh partition can only be lit by 6 lightbulbs at max. If 7 lights try to lit the same mesh partition, this partition will flicker.

Live example (In this video, when the player wield his torch, an additional light is cast on the surrounding meshes, making the issue extremely apparent) :

Mesh-partition flickering

In order to prevent this mesh-partition issue, advanced lightbulb mods provide new meshes, more partitioned than the vanilla ones. Here is an illustrated example from ELFX :

Non partitioned

Partioned

As you can see, the huge partition from the 1st screen (vanilla) includes the floor, the stairs, and the part under the door.
In the second screen (ELFX), it have been split into several small partitions. Only one of those sub-partitions is selected in the capture. The original big partition is now broken down into smaller ones, preventing the flickering that would be caused by 4 lightbulbs in the 1st floor (lighting the stairs), and 3 other lighting the 2nd floor (lighting the floor) leading to a total of 7 different sources lighting the same partition.

Some lightbulbs mods

Here are some example of some "lightbulbs" mods:

• Enhanced Light and FX (only cover lightbulbs in interiors)
• Enhanced Light and FX - Exteriors (only cover lightbulbs in exteriors)
• Relighting Skyrim
• Realistic Lighting Overhaul - Major City Interiors
• Realistic Lighting Overhaul - Major City Exteriors
• Realistic Lighting Overhaul - Minor Cities and Town Interiors
• Realistic Lighting Overhaul - Dawnguard Interiors
• Climates Of Tamriel - Dungeons (Hardcore and Hazardous) (only disable several lightbulbs in dungeons).

Lighting

This section is about interior cells only.

The whole lighting scene isn't only dependent on the lightbulbs in an interior cell. Several parameters are directly dependent on the cell itself.

Mods that edit those parameters directly conflict with other mods modifying this cell's data such as ownership, acoustic space, music, etc.

Example of lighting mods :

• Enhanced Lighting for ENB - ELE
• ELFX - Enhancer
• ELFX - Hardcore
• Dark Dungeons for ENB
• Realistic Lighting Overhaul - Dungeons
• Climates Of Tamriel - Interiors (Cold and Warm) (only modify imagespaces).

Lighting Template/Properties

Lighting is handled by several properties. Most of those are first set with a lighting template, and eventually tweaked manually by the modder on a per-case basis to achieve the final effect. There are 3 sub-families of lighting :

• Ambient Lighting : Set the ambient light color.
• Directional Lighting : Set the color that will be reflected on FX such as fog/myst.
• Fog Lighting : Set the color of the fog, this greatly impacts the feeling of the scene.
• Imagespace : Set a post-processing method for the scene.

Lighting mods alter those settings in two ways :

• By editing the lighting template, applying their light adjustments to all of the cells using this template.
• By editing the Cells themselves on a per-case basis, overriding the generic settings from the template.
• BY editing the imagespace, applying their modifications to all of the cells using this imagespace.

Interior Fog

Interior fog have more properties than just its color. Especially its distance.
A "close" fog will lead to reduced visibility, possibly preventing the player to see the end of a room/corridor he is in, while a very far fog will let him see very far.

Imagespace

An imagespace is an in-engine post-processing template used to further tweaks the visuals. This handles bloom, depth of field, sharpening, saturation, etc.

Here are two examples from the Creation Kit wiki to see how image space can affect the visual of a cell :

Azuras Star Imagespace

Frostmere Crypt Imagespace

Imagespace and Lighting Templates/Properties are designed to work together. For consistent visuals, you should not use the light properties of a mod, and the imagespace from another, event though those won't display as direct conflicts in xEdit.

Fake Exterior lighting

Cells can be marked "Use Exterior Lighting", and then assigned to a region (regions are how weathers are distributed through the game). This is used in cells that have a see-through ceiling, allowing the clouds from the outside weather to be visible, and benefit from day/night lighting variations.

Cells using this system are marked with the "Show Sky" flag.

Weather

Weathers are to a worldspace what the lighting is to a cell. Among other things, It can handle

• The ambient colors.
• The color spread by the sun (equivalent to the "directional lighting" for interiors, but doesn't affect shadowed area) which can affect the final color of the textures : A red-ish sunlight color on a blue-ish snow texture can result into green-ish snow.
• The colors of the sky.
• Everything related to the exterior fogs
• Several layers of clouds (both their texture and their colors).

As for cell lighting, a weather has a dedicated imagespace attached.

An important difference is that weathers have 4 "states" : Day, Night, Dusk, Dawn.
All "night darkness" mods are actually basic weather mods which only alter the ambient colors during the night states to be darker. "Darker nights" mods have to be tailored for a specific weather mods, otherwise they directly conflict with a weather mod (either the visuals from the weather mod are applied, or those for the darker nights, depending on the load order.)

Finally, weathers can also have a "precipitation type", such as rain/snow (which is just a flat overlay), or a special visual effect for more advanced rendering (such as Vivid Snow).

Some example of weather mods altering the look/feel of vanilla weathers :

• Pure Weathers
• ELFX - Weathers
• NLA Weather Plugin
• Realistic Lighting Overhaul - Weathers
• Realistic Lighting Overhaul - Dawnguard Weathers

NOTE:

Although it doesn't add any new weathers, Pure Weathers edit region settings to make more of the (modified) vanilla weathers seen in each region
ELFX Weathers and the NLA plugin also add a few new weathers and edit region settings to include them in the world, but their main purpose remain to modify the visuals of the vanilla weathers.

This is also important to note how the weather-system works in Skyrim. The map is divided into "regions". Here is a map of Skyrim with all the regions defining weathers from vanilla :

Each region has a set of potential weathers. Advanced weather mods (which can be considered as "climate mods") don't only modify the feel of the weathers, but also directly edit region settings to add/remove weathers from the list, adding to the variety of weathers seen across all of Tamriel. Most known mods to do so are :

• Climates of Tamriel
• Vivid Weathers
• Expanded Snow system

NOTE:

Climates of Tamriel is a specific case. It doesn't edit the vanilla weathers at all, but modify the region settings so those weathers aren't seen anywhere

Region settings don't only handle the weathers of the area, but also the ambient sounds for the surroundings. Mods adding new ambient sounds such as Audio Overhaul for Skyrim or Sounds Of Skyrim - The Wilds will conflict with weathers mods editing region settings to alter the weather distribution.

ImageSpace Modifiers

Imagespace modifiers (ISMods for short) are similar to imagespaces, but weren't originally intended to be applied permanently. They were meant to modify the imagespace during special events like spell casting (the most typical example is the Night Eye effect).

However, some mods use them to adjust the visual feeling of the game, which is in essence "casting a spell that last forever". The best known mod providing such a feature is Imaginator.

Imagespace modifiers don't directly conflict with anything. They don't "override" the current Imagespace, but are applied on top of it. However, they can lead to inconsistent visuals as they apply changes in a generic fashion (increasing the saturation will increase the saturation in any situation, which can wipe out the gloomy feeling intended by a specific mod in a specific weather or area).

Several settings of ISMods also tend to freak-out ENBs.

Post-processing

Post-processing mods (SweetFX/ICBINE, ReShade, ENBseries) essentially serve the same purpose as a mod applying ImageSpace Modifiers. However, they directly rely on DirectX features instead of the in-engine post-processing, offering high-quality features, and can alter way more things (ENBs can completely revamp the fog, which is impossible to achieve with imagespace modifiers).

The "big question" is "why do ENB Preset authors say their preset is designed for a specific weather/lighting/water mod"?

• Water : This is usually more a recommendation than an actual compatibility issue. ENBs have several settings to affect the way the water looks, but the differences between water mods are too faint to lead to any weird visuals on this side.
• Lighting :
  • Lightbulbs mods have nothing to do with post-processing and all are compatible with any ENB preset, as explained before they only aim to improve the lighting consistency. Some colors are affected by the ENB (warmer firelight, more intensity, ...) which can change the atmosphere, but won't produce serious visual glitches.
  • Lighting mods are indeed affected by post-processing. Though the features available in ENBs for interiors aren't as fleshed-out as they are for weathers, interiors-focused presets are greatly affected by the lighting mod used. A good thing to keep in mind however, is that most ENB presets available are essentially focused on exteriors and not interiors, and will generally work with most interior lighting mod.
• Weather : ENBseries is able to recognize which weather is currently active, and adjust post-processing in consequence. Advanced/High-quality presets all include weather-specific post-processing, tailored for a specific weather. If the post-processing has been tailored for a bright blue sky with bright white clouds, but the weather mod used change those into a orange-ish sky with pink-colored clouds (Yes, this happens. Most weather mod actually use those colors for dusk), the final visual will look weird, at best. On top of that, new weather introduced by the mod won't be recognized at all, which will lead the preset to use a "default" post-processing. Since most of the post-processing is handled on a per-weather basis, most of the preset's features won't show up at all on new weathers.