Open Door Blueprint

This lesson builds a door Actor that opens when the character enters its trigger area and closes after the character leaves. Overlap events change a Boolean state; Tick uses that state to choose an opening or closing rotation function. The demonstration includes a useful hierarchy correction: the trigger must remain in place while the door swings.

The scene uses a side-scroller template and an imported box-shaped door. Starter Content is present but not required for the mechanism. The exact Unreal Engine release is unidentified. The resulting interaction is demonstrated in the example level, without a player-only overlap filter, multiple-occupant handling, or frame-rate-independent rotation.

Prepare the hinge at the imported asset’s origin

At 00:01–04:01, the instructor imports the door as a static mesh and creates an Actor Blueprint to contain it. The door asset’s pivot is at a lower corner where the hinge should be, rather than at its center.

The source illustrates this in Houdini by offsetting box geometry so the intended hinge position coincides with the origin before export. In that recorded workflow, the imported mesh then rotates around the desired corner. The half-unit offset shown for a unit cube is an explanation of that example, not an offset to copy onto every door.

Check the imported mesh’s actual rotation pivot before constructing the interaction. A centered pivot makes the door spin about its middle even when the Blueprint’s rotation logic is correct. The video does not establish that every DCC and FBX export configuration treats object transforms and pivots identically.

The raw mesh placed for inspection is not the final interactive object. The Actor Blueprint becomes the object placed in the playable level.

Fit a trigger that covers the approach to the door

During 04:01–07:00, a Box Collision component is added to the Blueprint. Its position and extents are adjusted around the imported door. The example door is approximately 100 units wide and 200 high, so the trigger’s center and half-extents are set in relation to those dimensions.

The trigger is also made thicker and offset toward the opening side. The intention is to activate the door before the approaching character reaches the swinging panel, including when approaching from the other side.

A placed Blueprint is aligned with the side-scroller’s playable path and tested. At this stage the collision volume exists, but it has no behavior attached. A correctly placed volume alone cannot animate the door.

These dimensions depend on the character, door, and desired approach distance. Inspect the trigger in the level rather than treating the example values as a complete collision specification.

Let overlap events set state and Tick perform the motion

At 07:00–12:00, Actor Begin Overlap sets a Triggered Boolean true, and Actor End Overlap sets it false. The default is false, matching a closed, inactive starting state.

Event Tick feeds a Branch that reads Triggered. The branch will eventually call the opening behavior when true and the closing behavior when false. The overlap event does not itself perform every animation step; it changes the state that Tick keeps checking.

The door mesh component is the target of Set Relative Rotation. The instructor repairs a missing component variable name before completing that connection. Check that the graph targets the movable door panel rather than the collision box or the entire Actor.

This separation makes diagnosis straightforward: first establish whether entry and exit change Triggered, then establish whether Tick reaches the intended rotation operation. A Boolean can change correctly while the motion path remains unconnected.

Add a signed yaw increment and fix the component hierarchy

During 12:00–18:02, the door’s relative transform is read and its rotation inspected. The intended field is yaw, identified by rotating the door in the viewport. The current yaw is combined with a signed increment and written back through Set Relative Rotation.

The first test opens in the wrong direction, so the increment’s sign is reversed. A Door Rotation Speed float then replaces the literal increment, with a negative step used for the demonstrated opening direction. This variable controls an amount applied during updates; the video does not convert it into a delta-time-scaled degrees-per-second speed.

The instructor temporarily bypasses the state condition to show that Tick supplies the repeated execution, then restores the condition. Without an angular limit, remaining inside the trigger makes the door continue rotating.

Another problem comes from hierarchy: the collision box is initially inside the door component, so it moves with the swinging panel. The instructor moves it back under the default scene root. The door and its trigger can then occupy separate roles—the panel rotates while the activation region remains in place.

Inspect the component tree, not just the apparent box position at rest. A trigger that looks correct in the closed pose can still sweep through the character if it inherits the panel’s rotation.

Add an opening limit and isolate the open function

At 18:02–22:01, a second Branch compares the relevant yaw value with the negative-90-degree opening boundary. The instructor corrects the comparison during setup, and the resulting test stops the door near the intended open position instead of continuing around.

The final narrated opening test uses a greater-than-or-equal comparison against negative 90. Because the captions do not fully resolve whether every comparison receives the current or proposed next value, do not infer a mathematically exact clamp from this description. Inclusive comparisons and step size can matter at the endpoint; inspect the actual graph and final yaw when reproducing it.

The opening nodes are collapsed into an Open Door function after the test. This organizes the state-dependent behavior without changing its purpose: update the yaw toward the open boundary while the condition permits movement.

Test both continuing to stand in the volume and leaving it. At this stage, leaving only stops the opening path; closing has not yet been connected.

Reverse the step for closing and test both approaches

During 22:01–25:00, the opening function is duplicated as Close Door. Its comparison is changed toward the zero-degree closed boundary, and the speed is multiplied by the opposite sign so the yaw moves back toward the starting orientation.

The false output of the Triggered Branch calls Close Door. The final test shows entry opening the panel and exit closing it, including approach from the opposite side of the example setup.

The narration uses a less-than-or-equal-to-zero closing condition. As with opening, verify the actual input pin and endpoint rather than assuming that a comparison automatically clamps the result. The source demonstrates the visible behavior but does not perform a systematic overshoot or variable-step audit.

The level has no enclosing wall around the door, so the recording proves the local interaction rather than a fully designed doorway. It also does not filter which actor causes overlap or track several simultaneous occupants. One actor leaving while another remains is a separate case that a single Begin/End Boolean does not resolve in the demonstrated graph.

The completed checkpoint is an inspectable state-driven door: a fixed trigger, a panel with an appropriate hinge, separate open/close functions, and tested entry/exit behavior. Timing independence, exact endpoint handling, occupancy rules, and collision behavior during the swing remain additional work.