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Multi-Texture describes the blending of multiple textures on the same surface.

Texture Splatting

Texture splatting is a method for blending multiple textures together on the same mesh, by painting a mask between them. Often Vertex Color is used to control the blending because vertex color is fairly cheap. Or a bitmap can be used (splat map) because it gives more control and avoids the gradient artifacts of vertex blending.

Modulation Blending

This method adds sharp details to the blend area, by mixing vertex color (for the larger blend) with grayscale textures (for the sharp detail blend). These grayscale maps are either stored in the alpha channel of each layer's normal map, or multiple maps can be channel packed into a single map. Usually the shader has a control for how sharp the transition will be, and sometimes you can use a vertex color or bitmap to control the sharpness.

Variation Blending

Methods for adding variation across a tiling texture.

Trim Sheets

- texturing techniques of Sunset Overdrive by Morten Olsen, Principal Environment Artist, Insomniac Games, at GDC 2015.

Blending Operations

When blending textures together, the surface's color (source) is combined with the background color (destination) in a linear way. Similar to the "Normal" blending mode in Photoshop. However there are many other blending methods available.

Blends UnrealEngineDocumentation.jpg Blends | Unreal Engine Documentation has blending functions that replicate common Photoshop methods.

Blends SourceDestinationMatrix.jpg Alpha Blend - Source/Destination matrix has visual examples for commonly available shader blending modes.

Blends InsightIntoPhotoshop7BlendingModes.jpg Insight into Photoshop 7.0 Blending Modes has the math behind many of them.


id Software's Megatexture tech uses Decals and multitexturing to create their terrain textures, which are then baked down in a preprocessing step into a huge texture sheet, that's dynamically loaded as you play the game. So it's not really multitexturing in the end, blending in real-time, instead it's a single colormap baked from a multitextured source. The Splash Damage wiki has an article about generating Megatextures for ETQW.

Megatexture in Rage, before decals and multitexturing. Image by id Software
Megatexture in Rage, after baking in the decals and texture layers. Image by id Software

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