Shaders and Texturing - An Introduction to Computer Graphics for Artists - page 207

Fig. 11.31 In this tile set example, colors on border edges correspond to map boundaries that tile
together
because no polygons will share any UVs. The advantage to tile sets is that it is
possible to have much more variety in the fi nal result than when tiling.
A tile set allows artists to create a unique overall pattern out of a small group of
tiles used as modular units. These are called tiles. A texture tile is not repeated
mechanically based on having its UVs stretch beyond legal UV space. Instead, the
tile pattern is literally etched into the model, and each quad is mapped to fi ll 0-1 UV
space. A Tile set , or group of tilable maps is then created and assigned to each quad.
This method increases the poly and UV count of your object, but has the advantage
of allowing more variety in the mapping solution because you can now mix and
match the positions of each tile (Fig. 11.31 ). This is usually suffi cient to completely
disrupt any Moiré pattern, and at the same time makes it very diffi cult for any
observer to detect any repetition. For variety, you can also fl ip or rotate the textures.
Tile sets are used frequently in video game development.
Tile sets are the primary reason for high poly counts in terrain objects. Although
the shape of most terrain is often enough to justify the poly count, even a completely
fl at terrain object will usually be broken into hundreds of thousands of quads to make
the best use of tile textures. Think of each quad as a picture frame for your texture
maps. Within each frame, you may rotate or fl ip your map to create up to 16 variants
for each tile. For your tiles to work properly, they must be designed well. If they are
designed well, most viewers will not be able to fi nd the seams between textures, and
probably won't have any idea they are looking at hundreds of small square maps.
A set of texture tiles does not have to be interchangeable at every angle with every
other tile, but every tile should tile on all four sides with one or more maps. Every map
should represent every detail you wish to represent in your terrain. For example, you
may want to have several different maps to represent different sections of a road.
Some could be muddy, others full of puddles, and some dry. In other places it might
curve out of the frame at a 60° angle, or in another place at 45°. All of these variations
must be represented so that you may create every tile confi guration that you need.