Texture atlas

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A Texture Atlas describes the method of packing many separate textures together into a single texture. Other common names for this are "decal sheet", "packed texture".

Atlases save texture fetches, which can help improve the frame rate.

Each of the textures can be tiled with themselves, just like a regular tiling texture.

The textures can either be cropped out of the atlas by adding more edges to the model and cutting up the texture coordinates (at the expense of increasing the vertex count), or the textures can be arranged as sub-tiles and cropped out using a shader (at the expense of increasing the shader instructions).

Atlas Methods

There are two common atlas methods: one divides a single bitmap into multiple sub-maps (this is usually what artists mean when they say "atlas"), the other method packs different grayscale maps into each color channel (this can be called a multimap or channel packing). The two methods are not exclusive, they can also be used together in the same bitmap.

An atlas of sub-maps.
Image by Stefan Morrell.
Channel packing and sub-maps, in the same texture layout.
Image by Tor "Snefer" Frick.

Tutorials

Gutters

When a game model is textured using a single texture sheet, the texture will have typically have UV'd areas (UV shells) and blank areas between them (gutters).

The width of the gutter needs to be wide enough to accommodate how much EdgePadding you need. This varies depending on how large the texture is and the texture filtering type used by the game renderer.

Packing Tools

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