code/__DEFINES/layers.dm

UNDERFLOOR_OBJ_LAYER	bluespace beacon, navigation beacon, etc
CATWALK_LAYER	catwalk overlay of /turf/open/floor/plating/plating_catwalk
WEED_LAYER	Alien weeds and node layer
ABOVE_WEED_LAYER	Over weeds, such as blood
ATMOS_DEVICE_LAYER	vents, connector ports, atmos devices that should be above pipe layer.
FIREDOOR_OPEN_LAYER	Right under poddoors
PODDOOR_OPEN_LAYER	Under doors and virtually everything that's "above the floor"
CONVEYOR_LAYER	conveyor belt
DOOR_OPEN_LAYER	Under all objects if opened. 2.85 due to tables being at 2.8
HATCH_LAYER	For hatches on the floor.
BELOW_OBJ_LAYER	just below all items
LOWER_ITEM_LAYER	for items that should be at the bottom of the pile of items
BETWEEN_OBJECT_ITEM_LAYER	A layer above objects (like structures) but below items
ITEM_LAYER	The layer on which items lay
UPPER_ITEM_LAYER	for items that should be at the top of the pile of items
ABOVE_OBJ_LAYER	just above all items
DOOR_CLOSED_LAYER	Above most items if closed
FIREDOOR_CLOSED_LAYER	Right under poddoors
PODDOOR_CLOSED_LAYER	Above doors which are at 3.1
WINDOW_LAYER	above closed doors
WALL_OBJ_LAYER	posters on walls
POWERLOADER_LAYER	above windows and wall mounts so the top of the loader doesn't clip.
ABOVE_LYING_MOB_LAYER	drone (not the xeno)
BIG_XENO_LAYER	above ABOVE_MOB_LAYER because it's used for shallow river overlays which clips with the top of large xeno sprites.
ABOVE_XENO_LAYER	for xenos to hide behind bushes and tall grass
FACEHUGGER_LAYER	For facehuggers
WEATHER_LAYER	For WEATHER
BELOW_FULLSCREEN_LAYER	blip from motion detector
FULLSCREEN_WEATHER_LAYER	Weather
FULLSCREEN_IMPAIRED_LAYER	visual impairment from wearing welding helmet, etc.
FULLSCREEN_FLASH_LAYER	flashed
FULLSCREEN_DAMAGE_LAYER	red circles when hurt
FULLSCREEN_BLIND_LAYER	unconscious
FULLSCREEN_PAIN_LAYER	pain flashes
FULLSCREEN_VULTURE_SCOPE_LAYER	Vulture sniper/spotter scope
FULLSCREEN_CRIT_LAYER	in critical
AREAS_LAYER	for areas, so they appear above everything else on map file.
EMISSIVE_PLANE	This plane masks out lighting to create an "emissive" effect, ie for glowing lights in otherwise dark areas.
EMISSIVE_RENDER_TARGET	The render target used by the emissive layer.
EMISSIVE_LAYER_UNBLOCKABLE	The layer you should use if you really don't want an emissive overlay to be blocked.
BALLOON_CHAT_PLANE	Plane for balloon text (text that fades up)
TYPING_LAYER	Bubble for typing indicators
LOWEST_EVER_PLANE	NEVER HAVE ANYTHING BELOW THIS PLANE ADJUST IF YOU NEED MORE SPACE
FLOOR_PLANE	Floor plane, self explanatory. Used for Ambient Occlusion filter
GAME_PLANE	Game Plane, where most of the game objects reside
ABOVE_GAME_PLANE	Above Game Plane. For things which are above game objects, but below screen effects.
ROOF_PLANE	Roof plane, disappearing when entering buildings
BLACKNESS_PLANE	To keep from conflicts with SEE_BLACKNESS internals
LIGHTING_PLANE	--------------- FULLSCREEN RUNECHAT BUBBLES ------------
RUNECHAT_PLANE	Popup Chat Messages
HUD_PLANE	HUD layer defines
PLANE_MASTERS_GAME	Plane master controller keys

Define Details

#define
ABOVE_GAME_PLANE

Above Game Plane. For things which are above game objects, but below screen effects.

#define
ABOVE_LYING_MOB_LAYER

drone (not the xeno)

#define
ABOVE_OBJ_LAYER

just above all items

#define
ABOVE_WEED_LAYER

Over weeds, such as blood

#define
ABOVE_XENO_LAYER

for xenos to hide behind bushes and tall grass

#define
AREAS_LAYER

for areas, so they appear above everything else on map file.

#define
ATMOS_DEVICE_LAYER

vents, connector ports, atmos devices that should be above pipe layer.

#define
BALLOON_CHAT_PLANE

Plane for balloon text (text that fades up)

#define
BELOW_FULLSCREEN_LAYER

blip from motion detector

#define
BELOW_OBJ_LAYER

just below all items

#define
BETWEEN_OBJECT_ITEM_LAYER

A layer above objects (like structures) but below items

#define
BIG_XENO_LAYER

above ABOVE_MOB_LAYER because it's used for shallow river overlays which clips with the top of large xeno sprites.

#define
BLACKNESS_PLANE

To keep from conflicts with SEE_BLACKNESS internals

#define
CATWALK_LAYER

catwalk overlay of /turf/open/floor/plating/plating_catwalk

#define
CONVEYOR_LAYER

conveyor belt

#define
DOOR_CLOSED_LAYER

Above most items if closed

#define
DOOR_OPEN_LAYER

Under all objects if opened. 2.85 due to tables being at 2.8

#define
EMISSIVE_LAYER_UNBLOCKABLE

The layer you should use if you really don't want an emissive overlay to be blocked.

#define
EMISSIVE_PLANE

This plane masks out lighting to create an "emissive" effect, ie for glowing lights in otherwise dark areas.

#define
EMISSIVE_RENDER_TARGET

The render target used by the emissive layer.

#define
FACEHUGGER_LAYER

For facehuggers

#define
FIREDOOR_CLOSED_LAYER

Right under poddoors

#define
FIREDOOR_OPEN_LAYER

Right under poddoors

#define
FLOOR_PLANE

Floor plane, self explanatory. Used for Ambient Occlusion filter

#define
FULLSCREEN_BLIND_LAYER

unconscious

#define
FULLSCREEN_CRIT_LAYER

in critical

#define
FULLSCREEN_DAMAGE_LAYER

red circles when hurt

#define
FULLSCREEN_FLASH_LAYER

flashed

#define
FULLSCREEN_IMPAIRED_LAYER

visual impairment from wearing welding helmet, etc.

#define
FULLSCREEN_PAIN_LAYER

pain flashes

#define
FULLSCREEN_VULTURE_SCOPE_LAYER

Vulture sniper/spotter scope

#define
FULLSCREEN_WEATHER_LAYER

Weather

#define
GAME_PLANE

Game Plane, where most of the game objects reside

#define
HATCH_LAYER

For hatches on the floor.

#define
HUD_PLANE

HUD layer defines

#define
ITEM_LAYER

The layer on which items lay

#define
LIGHTING_PLANE

--------------- FULLSCREEN RUNECHAT BUBBLES ------------

#define
LOWER_ITEM_LAYER

for items that should be at the bottom of the pile of items

#define
LOWEST_EVER_PLANE

NEVER HAVE ANYTHING BELOW THIS PLANE ADJUST IF YOU NEED MORE SPACE

#define
PLANE_MASTERS_GAME

Plane master controller keys

#define
PODDOOR_CLOSED_LAYER

Above doors which are at 3.1

#define
PODDOOR_OPEN_LAYER

Under doors and virtually everything that's "above the floor"

#define
POWERLOADER_LAYER

above windows and wall mounts so the top of the loader doesn't clip.

#define
ROOF_PLANE

Roof plane, disappearing when entering buildings

#define
RUNECHAT_PLANE

Popup Chat Messages

#define
TYPING_LAYER

Bubble for typing indicators

#define
UNDERFLOOR_OBJ_LAYER

bluespace beacon, navigation beacon, etc

#define
UPPER_ITEM_LAYER

for items that should be at the top of the pile of items

#define
WALL_OBJ_LAYER

posters on walls

#define
WEATHER_LAYER

For WEATHER

#define
WEED_LAYER

Alien weeds and node layer

#define
WINDOW_LAYER

above closed doors

code/__DEFINES/layers.dm

Define Details

#define ABOVE_GAME_PLANE

#define ABOVE_LYING_MOB_LAYER

#define ABOVE_OBJ_LAYER

#define ABOVE_WEED_LAYER

#define ABOVE_XENO_LAYER

#define AREAS_LAYER

#define ATMOS_DEVICE_LAYER

#define BALLOON_CHAT_PLANE

#define BELOW_FULLSCREEN_LAYER

#define BELOW_OBJ_LAYER

#define BETWEEN_OBJECT_ITEM_LAYER

#define BIG_XENO_LAYER

#define BLACKNESS_PLANE

#define CATWALK_LAYER

#define CONVEYOR_LAYER

#define DOOR_CLOSED_LAYER

#define DOOR_OPEN_LAYER

#define EMISSIVE_LAYER_UNBLOCKABLE

#define EMISSIVE_PLANE

#define EMISSIVE_RENDER_TARGET

#define FACEHUGGER_LAYER

#define FIREDOOR_CLOSED_LAYER

#define FIREDOOR_OPEN_LAYER

#define FLOOR_PLANE

#define FULLSCREEN_BLIND_LAYER

#define FULLSCREEN_CRIT_LAYER

#define FULLSCREEN_DAMAGE_LAYER

#define FULLSCREEN_FLASH_LAYER

#define FULLSCREEN_IMPAIRED_LAYER

#define FULLSCREEN_PAIN_LAYER

#define FULLSCREEN_VULTURE_SCOPE_LAYER

#define FULLSCREEN_WEATHER_LAYER

#define GAME_PLANE

#define HATCH_LAYER

#define HUD_PLANE

#define ITEM_LAYER

#define LIGHTING_PLANE

#define LOWER_ITEM_LAYER

#define LOWEST_EVER_PLANE

#define PLANE_MASTERS_GAME

#define PODDOOR_CLOSED_LAYER

#define PODDOOR_OPEN_LAYER

#define POWERLOADER_LAYER

#define ROOF_PLANE

#define RUNECHAT_PLANE

#define TYPING_LAYER

#define UNDERFLOOR_OBJ_LAYER

#define UPPER_ITEM_LAYER

#define WALL_OBJ_LAYER

#define WEATHER_LAYER

#define WEED_LAYER

#define WINDOW_LAYER