UV coordinates inaccurate, showing nearby pixels when not supposed to So I have a blend that was given to me. Each patch of grass mesh for example, is neatly on the grass texture. All of the grass cubes throughout the map share this same UV space. However for no obvious reason to me, it's showing the nearby rock texture.

This is a megatexture so clamping isn't going to do anything as the entire level is a single texture but I shouldn't have to clamp in the first place.



If you zoom in very close on the UVs you can see that each corner of a single grass UV mesh is not touching the gray part in any part of that image. All of the grass is sharing the same UV space as well.



Why is this happening and how can I fix this? The level is only a single texture. Ideally I don't want to have to go around the map selecting all of the grass, rock, wood, etc, just to fix what seems like a blender bug.
This is not a bug, it is in the way UV-Mapping to a surface works. If the surfaces are at an angle, a certain amount of edge blending is going to occur. This can lead to unwanted seep-through of other parts of the texture.

It appears that the bleed in your texture is too small. Bleed is the amount of overfill that each island gets added on its edges. This in turn is causing the neighboring textures to show through. To get around this, you need to increase the spacing between the UV-islands.