42  Specials, Switches & Teleporters

This tour examines how Doom handles level specials, switches, and teleporters for triggering effects and moving entities.

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42.0.1 Special Effects Initialization

p_spec.h
- P_SpawnSpecials: Initializes level specials like lighting, doors, and platforms when a map loads.

p_spec.c
- P_SpawnSpecials(): Processes sectors and lines at load time, creating thinkers for special behaviors. - Type 48 lines scroll textures: handled for animation updates.

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42.0.2 Switch Logic

p_switch.c
- P_InitSwitchList: Fills switchlist[] with on/off texture pairs.
- Switch toggling uses XOR (i^1) to find texture pair and plays a sound.
- Switch activations schedule effects and update textures.
- P_UpdateSpecials: Restores original wall texture after button timer expires.

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42.0.3 Teleportation

p_telept.c
- Teleporters are triggered from the back side only. - EV_Teleport: Finds teleport landing spots (MT_TELEPORTMAN) via sector tag. - P_TeleportMove: Moves the object, adjusts height and view position.

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This completes the tour of specials, switches, and teleporters in Doom’s core logic.