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Link a button or a lever to a door

By the end of this page you have a door in your level that opens and closes from a button, a lever, or both. No graph to open: you place a few actors and pick the door with the eyedropper.

If you have not read How interaction works, here is the short version. The button or lever holds a list of Targets. Every target gets a message when it fires.

  • The doors: Content/MPFriendslop/Blueprints/Environments/Doors/ (BP_SlidingDoor_Double is in its Childs/ subfolder)
  • The button and the lever: Content/MPFriendslop/Blueprints/Environments/Fixtures/

The pieces

Actor What it is
BP_SlidingDoor_Double A double sliding door. Its two leaves slide into the wall. It opens only when something tells it to
BP_InteractButton A button you use with E. Each use flips its targets: open becomes closed, closed becomes open
BP_LeverBase A lever you drag with the grab button (Left Mouse Button). Pull it past its threshold and it is on, push it back and it is off

BP_SlidingDoor_Single is a different kind of door: players drag it open by hand. It has no link, and a button cannot open it. Pick BP_SlidingDoor_Double for anything a button or lever drives.

Place the door

The leaves slide sideways into the wall, so the wall around the door needs room for them.

  1. Place SM_Mod_Wall_Doorway_400 as the wall that holds the door.
  2. Place one SM_Mod_Wall_DoorPocket_200 on each side of it. In the doorway wall's space: the right one at (400, 0, 0), the left one at (0, 0, 0) rotated 180 on Z. The leaves slide into these.
  3. Drag BP_SlidingDoor_Double into the level and put it at (200, 0, 0) in the doorway wall's space. Its pivot is the centre of the doorway at floor level.
  4. If the door must start open, tick Is Open on the placed door.

Use the pockets, not a plain wall: a plain wall beside the door sits right in the leaves' path.

  1. Drag BP_InteractButton into the level and put it on the wall next to the door, out of the leaves' path.
  2. Select it, then select its BP_ActivationLinkComponent in the Details panel.
  3. Add an entry to Targets and use the eyedropper to pick the door.
  4. Set Prompt, Type and Duration on the button.

A button has no state of its own and no press animation. What the player sees is the door moving.

Field Where What it does Default
Targets the button's BP_ActivationLinkComponent The actors this button flips. Add as many as you want empty
Prompt the button The line under the ring. The shipped map uses Toggle Door Press Button
Type the button Simple, Hold or Spam. How the player uses it Simple
Duration the button Seconds to hold the key when Type is Hold 0
  1. Drag BP_LeverBase into the level and put it on the wall. Its base sits flat against the wall.
  2. Select its BP_ActivationLinkComponent.
  3. Add an entry to Targets and pick the door with the eyedropper.

The lever has two notches. Once it passes Activation Alpha, it tells its targets "on", and when it comes back below, "off". A door takes on as open and off as closed.

Field Where What it does Default
Targets the lever's BP_ActivationLinkComponent The actors this lever switches empty
Activation Alpha BP_LeverBase How far along its travel, from 0 to 1, the lever counts as on 0.5

How the lever feels in the hand (its travel, its notches, how heavy it is to drag) is covered in Make your own door, switch or lever.

The door's fields

Field Where What it does Default
Is Open BP_DoorBase The door's state. Tick it on a placed door to start open off
Move Duration BP_DoorBase Seconds for a full open or close. 0 snaps it 0.8
Open Travel BP_SlidingDoor_Double How far each leaf slides, in cm 114

A door that is not moving does not tick, so a level full of closed doors costs nothing.

Things to know

  • Put a control on each side of the door. The shipped map does this. A door closed from one side with its only button on the other side traps the players.
  • One control can drive several targets. Add more entries to Targets: one button can open two doors, or a door and the extraction hatch. The hatch is linked the same way, see Place an extraction point.
  • A button and a lever on the same door both work, but they speak differently. The button flips the door. The lever says on or off. So after someone presses the button, the lever's position no longer matches the door.
  • The leaves do not push players. They move straight to their position without checking what is in the way.

Warning

A target that cannot be switched does nothing, with no error. If you pick BP_SlidingDoor_Single, a wall or any actor that does not implement BPI_Activatable, the button still shows its prompt and nothing happens.

The dispatchers

Dispatcher Where When it fires Fires on
OnDoorStateChanged BP_DoorBase The door starts to open or close. Gives Is Open every player
OnAxisAlphaChanged the lever's BP_GrabAxisComponent The lever moved. Gives Alpha, from 0 to 1 every player

To make a button switch your own actor, or to build your own door, see Make your own door, switch or lever.

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