What is texel density ? | Timothy Dries

[Carlosan]

In short, smaller objects in the scene should use fewer pixels than bigger objects.

If a UV island is scaled correctly according to its size in the scene, 3DCoat will color the island grey.

Islands that are using more pixels than they should are colored red and islands using less than they should are colored blue

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Texel density (also referred to as pixel density or texture density) is a measurement unit used to make asset textures cohesive compared to each other throughout your entire world.

It’s measured in pixels per centimeter (2.56px/cm) or pixels per meter (256px/m).

 

Importance to games

In games, you quickly notice when there is a disconnect between items in the world when one item’s textures look blurry and the other looks crisp. This is often caused by a mismatch in texel density and can pull the player out of that immersive feeling we’re trying to create.

While the resolution of these textures itself can change between games and game types, texel density is about a consistent measurement value that’s game-wide.

It’s also important to developers and specifically artists because it gives them a goal to work with when it comes to texture resolution and it also stops them from going crazy with trying to make everything look detailed and forgetting about the bigger picture. This is important when trying to create full environments or even entire worlds.

 

What is a texel?

Texel stands for TEXture pixEX or texture element. You can compare this to the relation between a pixel that makes up an image, but in this case it’s a texel that make a texture map. Making a texel the smallest element that represents a texture map.

A GPU (Your Graphics Card in your PC) takes these texels and projects them onto the pixels on your screen through texture mapping (This is why we have UV’s)

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TEXTURE SIZE AND SCALE INFLUENCE

Your texel density depends on two things, OBJECT SIZE and the TEXTURE RESOLUTION.

 

THIS MEANS:

Higher texture resolution & same object scale = Higher Texel Density (Less blurry texture)‍

Same texture resolution & higher Object scale = Lower Texel Density (Blurrier Texture)

 

HOW TO CHOOSE TEXEL DENSITY

Screen relation method
One way of calculating texel density is to see how close you can get to your assets in your game, see how big it is on screen and relate this size (In pixels) on your screen to your texture size.

For personal projects
Make it look as good as possible, and use recent game art as examples. Something like 20.48px/cm will be more than enough to work with.
My advice would be to not go crazy with using 8k or 16k textures, show that you are capable of working within game art restrictions.

Just make sure that you can’t really see any obvious pixelation on your asset that gives away that it’s a game asset look.
This goes hand in hand with making good UV’s and having appropriate textures as well though, so keep that in mind.

 

HOW TO CALCULATE IT
If you want to do it manually it’s best to start with a simple wall for your environment, ideally make it a 1 by 1 meter section, so the calculation becomes really simple.

[Carlosan]

APPROACHES IN DIFFERENT GAMES
First Person Game
Games where we are the eyes of the main character allow us to also look at things really closeby, so these games usually have the highest texel density to compensate for this fact.

 

Third Person Game
These games are usually further away from the visual aspects of the scene itself. So we can go for a slightly lower texel density and maybe replace this with more asset density.

 

Top Down Game
The games that are usually the furthest away from the camera, so no need to go crazy on the texel density for these and it can be lower. Usually items that can be inspected or are more important will receive a bigger texel density.

DIFFERENT WORKFLOW IMPACTS
While not dependant on the workflow, some workflows might need a different approach to texel density or can optimise the way they tackle.

 

Unique assets

Texel Density for Unique Assets is pretty simple, you can just use a texel density tool to get as close to the desired texel density as possible, making sure you use the most of your UV space.

You can also scale up or down UV islands depending on how much of the assets will be visible or the importance of that part of the asset.

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Tileable Textures

It’s easy to stick to the texel density for tileable textures, you can just use your texel density calculator for that.

Talk about how many times you want to tile a tileable texture on a surface based on the texel density.

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Trimsheets

For trimsheets you want to match your trimsheet layout as well as match the texel density of the scene. So first apply the texel density to the UV islands (or asset) and then scale them towards the sections that fit the closest to that.

Usually, the limit here is something around 25% up or down, big enough to give some freedom but small enough to not break visual consistency either.

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ESTIMATION WITH PROXY MODELS

For a quick estimation you can always take the rough dimensions of your current model or even make a proxy model that encompasses the model itself and then do a quick calculation based on that to know if.

This is really helpful when you don’t have the object modelled yet and want to check what texture size you will be needing. If you’ve done this a couple of times you might even get quick enough to skip the proxy model all together and do a rough estimation yourself.

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OPTIMISATION OVER DISTANCE
A lot of optimisation happens in game engines already (With LEVEL OF DETAIL Meshes and MIP MAPPING) and artists can have an input on it if needed, but it’s less and less of a requirement with rendering techniques becoming less and less limited by technology.

Vista Meshes

There are exceptions to this though, like specifically created Vista LOD Meshes, which are meshes rendered at higher detail then what they would normally would be at that distance. This is super useful for big landmarks or points of interest that are important for player navigation.

Manual Optimisations
There might be moment where you need to go into certain area’s and manually optimise them for performance as needed. This might mean a bunch of different things, lowering the texture resolution (Thus lowering the texel density) or even manually optimising LOD meshes.

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WHEN TO DEVIATE FROM IT
There are situations in games where the team behind it decides to break texel density. Most of these have to do with importance to the player or where you can get really close to the asset itself. Some examples include weapons in first person games, assets that will be shown in special cinematics, menu or inspectable objects or maps that need extra detail because they help the player navigate the game world, to name a few.

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Scaling in some in house engines
This came to a surprise to me as well, but a lot of the in house engines I’ve worked with prohibit (or block you from submitting to source control) when you are trying to scale items. And is partially done to keep a consistent look in the game but not allowing you to break texel density. (might also have some other consequences? or impacts?)

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SOURCES
- Texel Density and other texture theory (https://antodonnell.gumroad.com/l/rHAIO)

- All You Need to Know about Texel Density - Leonardo Lezzi (Texel Density: All you need to know HQ PDF)

- Texel Density : What It Means & How To Use It (https://youtu.be/Za5AIQXwqCs)

- Discussion: Talking Texel Density (https://youtu.be/ZL5nToMpjp8)

- What is Texel Density and How to Master it (https://youtu.be/5e6zvJqVqlA)

- What is Texel Density? - A Layman's guide. (https://www.artstation.com/artwork/qA1lDy)

- Understanding Texel Density (https://youtu.be/rWJRekLpXXU)

- How to find the right texel density for your asset (https://youtu.be/iL2iXizf9xM)