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Rotorz Tile System for Unity
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Edge Correction

Bleeding will usually occur at the edges of tiles due to texture filtering and/or mip-mapping. Two popular ways to reduce the visibility of such artifacts is to either inset UV coordinates by half a texel, or to add borders around the edges of each tile in your atlas.

Illustration of bleeding between tiles.
Figure 6-1. Example of bleeding between tiles due to texture filtering

As depicted above, lines appear between tiles which often flicker when movement occurs (camera movement, zooming, tile movement, etc). The effects of edge bleeding can sometimes be counteracted by carefully packing tiles adjacent to other similar tiles.

Why does bleeding occur?

Edge bleeding occurs when multiple tiles are packed into an atlas texture because pixels are incorrectly blended between adjacent tiles.

Illustration of atlas showing cause of edge bleeding.
Figure 6-2. Example atlas (left) where edge bleeding occurs (right)

Each of the following can lead to this undesirable effect:

  • Texture filtering
  • Mip-mapping
  • Lossy texture compression
  • Use of Non-Power-Of-Two (NPOT) atlas texture
  • Sub-pixel placement of tiles
Tip
Tip
Where possible avoid using lossy texture compression when working with tileset atlas textures. If you switch the texture inspector into advanced mode you can pick from a range of texture formats on a per platform basis.