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Material

I should start a betting pool on the name of the next algorithm.
Solid Tile Based Giga Clipmap Splatting?

Besides the geometry a landscape also needs materials. It provides the texture to put on the terrain and how to blend them with each other.

Virtual Textures
These are techniques based around the concept of virtual textures, it's like a big, really big texture.

Adaptive Virtual Textures - 2014
Instead of a virtual texture over the whole terrain chunks of the terrain is assigned virtual texture space at run-time. How much each chunk gets depends on the importance of the chunk so a chunk close by gets more details. Chunks can get it's virtual texture size downgraded or upgraded at run-time.

Procedural Virtual Textures / Shader Splatting - 2009
Use a virtual texture over the terrain but fill it in at run-time.

Mega Texture - 2007
This is the first logical step when one has a really big texture. Stretch it over the whole world and make people paint it however they wish. Used in IdTech4 (Enemy Territory: Quake Wars), IdTech5 (Rage, Wolfenstein: The New Order) and IdTech6 (Doom). The downside of mega textures is a really big set of data to store/load and lots of texture space for artists to paint.
Blending
Texture Splatting - 2000
Each texture that is used on the terrain also have a alpha mask texture. The mask is stretched over the whole terrain and it selects how much of each texture should be blended in at that location of the height map.

Vertex Splatting - 2000
Each vertex has a vertex color or other per vertex data that tell how much of each texture should be used at that vertex. So if the vertex color is used then four textures can be blended onto the terrain. This is like a lower detail version of texture splatting but it makes it possible to avoid a texture switch on each height map if many of them are used.

Terrain coloring -
A single gray scale noise texture is tiled all over the terrain to provide the details. A single color texture is stretched over the whole terrain and it is mixed with the noise texture to provide the final result.

Other

Tile - 1994
Each quad (tile) in the heightmap is given it's own texture. A 32x32 heightmap needs a 31x31 tag map that tell what texture each tile should use. The tag need to contain the index of the texture to use and can also include how it will be rotated or flipped when placed on the tile. Transitions between areas such as grass to sand is done by making transition textures for each possible combination.

Solid - Around the time of the Fall of the Western Roman Empire
Set the background color to light blue for the sky and green for the ground.


Reference
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