From Mod Wiki

Mapshots are screenshots taken with the mapshot command they are rendered without perspective projection so they look like a "map" (as in a roadmap :) )

The command is mapshot <filename> [size] [blends] [tiles] (only the first parameter is required; the others are optional.)

  • filename - the name to store the result, if tiles is set to a value greater than 1 this is the filename prefix.
  • size - size in pixels of a single tile
  • blends - number of AA passes to do (this is the same as the blend from normal screenshots)
  • tiles - number of tiles to output on one axis (this means there will be Tiles * Tiles amount of images output!)

Mapshots need to be taken in game, with the map loaded, in 640×480 mode. Use r_mode 3 and r_aspectratio 0 followed by vid_restart on the console. You may need to enable com_useFastVidRestart 1 before vid_restart will work.

The reason there is a tiles option is because of the way the MegaTexture works. The area of high resolution detail around the camera is limited, so by splitting the whole map in several tiles the high resolution parts of the MegaTexture will be centered around the tile's center. Using a single tile for the whole map will essentially mean that the high resolution detail is only used in the center of the map.

The number of tiles you want depends on the final size of the mapshot you need, if the image is going to be smaller than 1024×1024 a single tile is enough. If it's gonna be 2048×2048 use two tiles etc... You'll probably never need much more than four tiles.