Default value
32 (depends on world.icon_size)
This var defines the height of the physical atom’s bounding box, in pixels. By default all atoms are assumed to be one tile in physical size.
Example: A 16×16 smiley face centered in a 32×32 icon should have a bound_height value of 16.
The default value depends on world.icon_size and world.map_format. In a topdown or tiled map_format, the icon height specified in world.icon_size is used. In other modes, height is irrelevant and tile “footprints” are square, so the icon width is used.