Arcane University:NIF Data Format

General NIF structure

NIF stands for "Net Immersive Gamebryo" file format. The technology was bought by Bethesda in the 90ies from Gamebryo, and modified since. They use BSShaderProperties and BSTextureSets to render meshes. NIF (Netimmerse Gamebryo) files in Skyrim are the files that hold the 3D Model information necessary to display objects in the game. When you open a NIF file in NifSkope, every NiTriShape represents a 3D Object instance. A single NIF file can have multiple instances of these and they can reside under various parent nodes. Make sure, that you visualize it as a tree diagram. Note that there is a hierarchical order, similar to shoulder -> arm -> hand -> finger. In theory, your mesh could be sorted differently, but most meshes look like this. If you see slight variations, don’t worry too much, the system behind is the same. The top-level is most commonly a BSFadeNode (static bodies) or a Ninode (Skinned rigged meshes) or a BSLeafAnim/tree node (plants). The BSX Flag below is for activating the collision. The bhkCollision object is the mesh of the collision. The first sublevel has the Nitrishape, which is the “body” of the mesh. There can be as many as you want. Each Nitrishape then has a second sublevel, which contains a NirtiShape Data tab and the LightingShaderProperty. This is where we set up the way the mesh is rendered. Here, we set the shader type and the shader flags and controllers. If you double click on the BSLightingshaderProperty, you find the third sublevel, the TextureSet, which contains your texture slots. Meshes can be rendered in Skyrim according to their BSLightingShaderProperty or the BSEffectProperty.

A NiTriShape can have the following child properties among others:

• NiTriShapeData is the actual mesh.
• BSDismemberSkinInstance is the information necessary to handle limbs being dismembered from the base mesh. Those nodes hold all skinning/rigging data. They tell the mesh how to deform during animation
• BSLightingShaderProperty holds lighting and texture information.
• NiAlphaProperty tells the game how to handle transparency in the mesh.

Nifskope Gamebryo NIF branch hierarchy example (object window):

Understanding BSShaderTextureSet textures and Skyrim

Textures are the only way for you to paint your mesh and make it look the way you want which means that, apart from the mesh itself, the textures will be the single most important work. As the mesh is built using triangular faces, to know what to draw on each face, you create what are known as UV Maps in Blender or 3D Studio Max. The UV Map is where you take the 3D triangles of your mesh and map them on to a flat plane. This way the game can project a texture back on to the mesh based on the information in this UV Map. It is therefore important to understand that when vertices are moved, they will stretch and shrink the face and can cause the texture to look strange. This is more an issue with how 3D engines work and not anything you can control. Just keep in mind and work around it if needed.

The shader will apply light and effects based on 2 things:

• The BSShaderTextureSet textures.
• Flags set for the BSLightingShaderProperty. Each flag only works with a specific set of textures.

Overview of the Texture Set Slots

Number	Name	Use	naming convention
SLOT 1	diffuse map	diffuse (RGB) + transparency (Alpha)	d.dds
SLOT 2	normal map	normal (RGB) + greyscale Specular (Alpha)	n.dds
SLOT 3	glow map	emissive (RGB) / subsurface color (RGB)	sk.dds
SLOT 4	bump map	greyscale height / parallax (RGB)	g.dds
SLOT 5	env. map / cube map	environment (mirror) / cube map (RGB)	e.dds
SLOT 6	material map	environment / reflection mask (RGB)	m.dds
SLOT 7	- map	inner layer diffuse (RGB) + inner layer depth (Alpha)	-.dds
SLOT 8	sst.m.	subsurface teint outer colour	s.dds
SLOT 9	-	-	-

Diffuse Map (Slot 1 of the Texture Set)

This texture is the base texture of the mesh and contains the main coloring your texture will use as well as the transparency information in the alpha channel. All other textures will only be detail additions and effects.

Compression:

Use DXT1 if transparency is not needed. Use DXT3 if only full transparency is needed. Use DXT5 if the texture needs partial transparency. Required properties:

For Alpha Transparency Automatically enabled for outer layer if using MultiLayer Parallax shader, otherwise requires that a NiAlphaProperty be added to the NiTriShape (right-click the NiTriShape > Node > Attach Property > NiAlphaProperty) NiTriShapeData > Has Vertex Colors NiTriShapeData > Vertex Colors Appearance Controller(s):

For Alpha Transparency NiAlphaProperty > Flags (Click the flag to view settings) BSLightingShaderProperty > Alpha 0 is fully transparent (invisible) 1 is fully visible (opaque) Transparency Map (Alpha Channel) Black is fully transparent (invisible) *dependent on NiAlphaProperty flag settings White is fully visible (opaque) *dependent on NiAlphaProperty flag settings Transparency increases as shade approaches black *dependent on NiAlphaProperty flag settings Suffix: none

The NiAlphaProperty

Click the flag icon next to flags to view the settings.

Enable Blending should be checked For Alpha Blending Source Blend Mode: Src Alpha Destination Blend Mode: Inv Src Alpha For Additive Blending Source Blend Mode: One Destination Blend Mode: One For Multiplicative Blending Source Blend Mode: Zero Destination Blend Mode: Src Color For 2x Multiplicative Blending Source Blend Mode: Dst Color Destination Blend Mode: Src Color For Alpha Testing check Enable Testing Alpha Test Function sets how transparency channel grey values (0 to 255 or black to white) will be compared to the Alpha Test Threshold value to determine what is opaque Less or Equal: Lighter will be more transparent Greater or Equal: Darker will be more transparent Alpha Test Threshold: Value from 0 to 255 (black to white) Color Blending

Color Blending Equation

(Source * SourceBlendMode) + (Destination * DestinationBlendMode)

“Source” is the color of the model materials in that pixel before blending “Destination” is the color of what is behind the model in that same pixel before blending The two values are modified by the value of the blend mode in that same pixel, then they are added together. Blend Modes (a.k.a. Blend Factor)

One: multiply by one (no modification) Zero: multiply by zero Src Color: multiply by “Source” Inv Src Color: multiply by inverse “Source” Dst Color: multiply by “Destination” Inv Dst Color: multiply by inverse “Destination” Src Alpha: multiply by value of the model’s alpha channel (diffuse and vertex colors) present at that pixel Inv Src Alpha: multiply by inverse value of the model’s alpha channel (diffuse and vertex colors)present at that pixel Dst Alpha: multiply by value of the background model’s alpha channel (diffuse and vertex colors)present at that pixel Inv Dst Alpha: multiply by inverse value of the background model’s alpha channel (diffuse and vertex colors)present at that pixel Additional information on color blending.

Normal Map (Slot 2 of the Texture Set)

The normal map, very similar to a bump map, will add the illusion of depth to the mesh. This is accomplished by creating varying shades of violet using various software including Mudbox, Zbrush, xNormal, Maya, the Gimp normal map plugin, or the Nvidia normal map plugin for Photoshop. Here is a video tutorial for creating high quality normal maps with ZBrush. The shader will then use the violet levels to determine the light levels for the texture, bending it if you wish, giving you what looks like height and depth details to the mesh.

Model Space Normal files created by Bethesda have the suffix _msn and are normal maps with no alpha channel. I prefer to use _n tangent space normal maps with the alpha channel instead of using another image and more video ram. I personally find the ability to add a specular alpha too good a thing to pass up.

It is important that NiTriShapeData > BS Num UV Sets is set to 4097 in NifSkope. If it is not, the Creation Kit, Nifskope, and the game itself will not display the Normal Map properly in-game.

The Alpha Channel of the Tangent Space Normal Map

The tangent space normal map’s alpha channel will be ignored in the Skyrim game engine for transparency and instead, the intensity of the different greyscale levels will determine how bright (specularity) that part of the mesh will be in-game.

Black is minimum intensity, no specular highlight. White is maximum intensity. Intensity increases as shade approach white. A quick and dirty way to make this brightness mask is to take your diffuse map and darken it substantially, then copy it in to the alpha channel of the normal map in Gimp or Photoshop.

Compression: Use DXT5 because of the importance of the alpha layer in this file. Bethesda uses DXT5 in all tangent space normal maps that I have observed.

Required properties:

NiTriShapeData >BS Num UV Sets = 4097 NiTriShapeData > Has Normals = yes BSLightingShaderProperty > Shader Flags 1: SLSF1_Specular Appearance Controller(s)

BSLightingShaderProperty > Specular Strength 1 is normal intensity Less than 1 is lower intensity Greater than 1 is higher intensity BSLightingShaderProperty > Specular Color The color of the specular highlight BSLightingShaderProperty > Glossiness Glossiness is the width of the specular highlight 10 is a wide specular highlight 50 is a thinner specular highlight 100 is an even thinner specular highlight Value ranges from 0 to 999 Suffix:

_n: Tangent Space Normal Map Required to use the alpha layer specular map. Tangent space normal maps are easily recognized by their mostly blue appearance. Tangent space normals almost always look bluish because normals in tangent space are always considered “up” (coordinates 0, 0, 1 ), even if in world space this is not true. The normals mapped on this triangle are thus encoded, and that’s the key point, relatively to ( 0, 0, 1 ). Because most normals are majorly “up”, and since the vector ( 0, 0, 1 ) is colorized as blue-purple-ish, the result is a blue-purple-ish normal map. The benefits of tangent space maps are the removal of the restrictions imposed by World Space and Object Space normal maps. Tangent Space normal maps can rotate and deform, therefore they are ideal for characters or objects that need to have vertex deformation, like water or tree limbs. _msn: Model Space Normal Map Does not have a specular alpha, SLSF1_Specular must be false. Slot 8 can contain a specular map if model space normals are used. Object Space normal maps can be moved, but the vertices of the mesh cannot be deformed or the shading is wrong. Object space normals are best for things that can move, but not deform, like swords, shields, doors, etc. Also note that the Creation Kit expects the normal map to be present for the mesh and will give an error message if not present.

Emissive (glow) Map (Slot 3 of the Texture Set)

This slot can either be used for an Emissive Map or for a Subsurface Color Map which is used in the MultiLayer Parallax section below.

The Emissive Map texture will add lighting to the mesh based on a few settings being set. The game will glow any color that you use / add but ignore black making this a very easy texture to apply. However, because you need to use Emissive Color for the glow base it may wash out the texture color. You may need to try different settings for this color but it will most often work fine if you use similar colors or set Emissive Color to a greyscale color.

Soft Lighting, also called wrapped diffuse adds a glow through the object to simulate light being diffused and passing through the object. Good for simulating semi-transparency on objects such as leaves.

Rim lighting is only visible when light is on the opposite side of the mesh and simulates light bending around the object and lighting it at the edges.

Compression: DXT1

Required properties:

BSLightingShaderProperty > Shader Type: Glow Shader BSLightingShaderProperty > Shader Flags 1: SLSF1_Own_Emit SLSF1_Environment_Mapping disabled BSLightingShaderProperty > Shader Flags 2:

SLSF2_Glow_Map

For Soft Lighting: SLSF2_Soft_Lighting For RIM Lighting: SLSF2_Rim_Lighting (Rim lighting overwrites soft lighting) Appearance Controller(s):

BSLightingShaderProperty > Emissive Multiple Glow intensity increases as emissive multiple increases BSLightingShaderProperty > Emissive Color Soft Lighting Specific Lighting Effect 1: Light begins in the center and higher values wrap the light further around the sides. Between 0-1 the effect also diminishes in strength such that 0.0 is completely off. Rim Lighting Specific Lighting Effect 2: Light begins on the edge and moves towards the center as the value increases. The lower the number, the more edges the light catches on. The higher the number, the sharper the effect appears. Suffix: _g

Height / Parallax Map (Slot 4 of the Texture Set)

This slot is used for a Height/Parallax Map. This is different from MultiLayer Parallax.

This is a greyscale image in RGB format. Height is determined by the darkness or lightness of each pixel as follows:

Mid grey (RGB 127,127,127) is zero depth and height Black is maximum depth White is maximum height Compression: DXT1

Required Properties:

An ENB is required for this texture to function properly. BSLightingShaderProperty > Shader Flags 1: SLSF1_Parallax Shader Type: Heightmap

Suffix: _p

Environment / Cube Map (Slot 5 of the Texture Set)

Environment/Cube Maps more or less add another layer of textures and can help get a more detailed look to your mesh. Cube mapping is preferred over other methods of environment mapping because of its relative simplicity. Also, cube mapping produces results that are similar to those obtained by high quality, slow rendering, but takes much less processing power – the moderate reduction in quality is compensated for by large gains in efficiency.

Also, cube mapping provides a much larger capacity to support real-time rendering of reflections relative to other mapping methods because the combination of inefficiency and viewpoint dependency severely limit the ability of these mapping techniques to be applied when there is a consistently changing viewpoint.

These maps are a bit different than other one layered textures:

A cube use 6 faces, counting 2 faces for each axis, xyz. Each face can be calculated with positive and negative x, y and z. They are sorted from +x, -x, +y, -y, +z and lastly -z. Each of these would be their own layer in an image editor, for instance, Gimp or Photoshop. Compression: DXT1

Required Properties:

BSLightingShaderProperty > Shader Type: Environment Map BSLightingShaderProperty > Shader Flags 1: SLSF1_Environment_Mapping BSLightingShaderProperty > Shader Flags 2: SLSF2_Glow_Map disabled Appearance Controllers:

BSLightingShaderProperty > Environmental Map Scale 1 is normal intensity Less than 1 is lower intensity Greater than 1 is higher intensity Suffix: _e

Greyscale / metalic cube map (Slot 6 of the Texture Set)

Environment/Cube Mask is a Greyscale Image. Simply a lighting control texture sometimes referred to as a specular map with the purpose to soften or diminish the level of light affecting the mesh reflection. Brightness of individual pixels determine the effect: white will reflect all light and black will reflect no light.

Compression: DXT1

Required Properties:

An environment/cube map is required. BSLightingShaderProperty > Shader Type: Environment BSLightingShaderProperty > Shader Flags 1: SLSF1_Environment_Mapping Appearance Controllers:

BSLightingShaderProperty > Environmental Map Scale 1 is normal intensity less than 1 is lower intensity greater than 1 is higher intensity Black is minimum intensity, environment/cube map has no effect in these areas White is maximum intensity Intensity increases as shade approaches white Suffix: _m

Subsurface Tint Map (Slot 7 of the Texture Set)

This slot is also used for Inner Layer Diffuse and Inner Layer Depth maps in MultiLayer Parallax which will be detailed below.

Subsurface tint maps are used for subsurface scattering. This is a rendering effect that simulates the diffusion of light inside a translucent medium. The effect can be seen as an extension on the principles of translucency and is appropriate for realistically simulating a wide range of materials including wax, marble, liquids (like milk), plant leaves, fruit, snow, and most importantly, human skin.

Compression: DXT1

Required Properties:

BSLightingShaderProperty > Shader Type: Skin Tint BSLightingShaderProperty > Shader Flags 1: SLSF1_FaceGen_RGB_Tint Appearance Controllers:

Brightness of the texture controls translucency while the game defines the underlying color (Set in the race menu.) Typically a very dark greyscale texture. Black is opaque White is entirely transparent Suffix: _s

Backlight Map (Slot 8 of the Texture Set)

Back lighting fills in the surface opposite a light. This is useful for faking translucency, like showing the bones in a dragon’s wings yet letting light bleed through the skin. The texture can be colored but like glow maps a high emissive value will wash that color out.

Compression: DXT1

Required properties:

BSLightingShaderProperty > Shader Flags 2: SLSF2_Back_Lighting Appearance Controller(s):

BSLightingShaderProperty > Emissive Multiple Glow intensity increases as emissive multiple increases BSLightingShaderProperty > Emissive Color Suffix: _b or _bl

The unused 9th slot

Slot09 – Currently Unused.

Shader Types

1.1. Bethesda Shader Properties 1.1.1. Environment/Reflection Requirements: cube map (also called) environment map BSLightingShaderProperty => Skyrim

• Default Shader

• Environmental Shader

The most commonly used BSLightingShaderProperties are Default shader type (“0”) and Environment Map shader type (“1”). You set your mesh shader property type in BSLightingshaderproperties. Note that each Nitrishape can only have one shader type and a small range of optional shader flags and use specific controllers(see below).

But, if needed, you can simply use multiple Nitrishapes combined on top of each other. As an example, it might make sense to split your mesh into subsections by material (metal, leather) and export each as a different Nitrishape (first sublevel) into the same mesh. Consider a leather armor for instance. I would suggest having an organic leather/cloth part (which usually absorbs light to a high degree and would use the default shader type) and the metal elements (which would reflect light stronger and profit from cube maps used in the environment map shader type).

Available Shader Flags, Controller Settings, and Texture Slots

BSLightingShaderProperty Shader Types BSShaderFlags Controller Settings BSTextureSets They have their own unique requirements. They need specific Texture Slots to be filled, depending on their character.

Most Common Shader Types

Default (0) Shader Type Default Shader Type

use: Assets with color, height, and specularity. common examples: rocks, clothes, furniture, stones, plants, sometimes metals if specularity is done in a way that can pretend metallic reflections. necessary slots: 1) base color/diffuse map 2) normal map with specularity in alpha channel (optional) necessary flags: those who are marked green above under shader flags, for export; and additionally what you need (vertex paint, specularity for example, if you learned how to apply these)

Example picture above, and shader settings of another example below.

The textures: 1) diffuse (base color) in slot 1, and 2) normal map with optional specularity in the alpha channel in slot 2 of the BSTextureSet.

Environment Map (1) Shader Type Comment regarding Parallax shaders

General Optimizations of the NIF

Sanitize Blocknames

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For details on textures, check Arcane_University:DDS_Data_Format.