DF24 and X1800

[NocturnDragon]

Just the plain neighbours in the texture map.

This feature is called Fetch-4 and with one texture fetch it can retrieve 4 neighboring texels (2x2 texel block) from a single-channel texture map.
Four individual samples of a single-channel texture are swizzled into RGBA channels when they are fetched from the texture. The swizzling of 2x2 texel block into 4 channels is illustrated by the following diagram. .

_____
|A|R|  --> (RGBA)
|G|B|