09 — VRLabBP: the Blueprint demo¶
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/InteractionSystem/Demo/VRLabBP/Maps/VRLabBP is a separate map in the InteractionSystem 1.0 plugin for Unreal Engine 5.8. In the Content Browser enable Show Plugin Content, open the map and press Play. Quest 2 uses OpenXR and Touch controllers; without a headset a two-hand emulator starts with the same keys as in VRLab. Tab and Backspace switch between the seven stations. The map does not change the existing InteractionLab, SpearRange and VRLab.
The scene has a light stone floor, cobalt walls, blue and turquoise accents, gold pointers and a red wheel. The bright palette with its parent instances is in /InteractionSystem/Shared/Materials. The VRLab map uses the same instances; changing a color updates both scenes without repainting the meshes.
Before playing open the step-by-step instructions for grabbing and using items: they explain how to place the palm spheres, hold two mouse buttons, take the bow and arrow, draw the string and shoot.
| Station | Blueprint actors | What to check |
|---|---|---|
| 01. Interaction and throwing | BP_PickupCube, BP_UseButton, BP_ThrowableSpear |
Take the cube, press the red button, throw the spear at the target. The button handles Interaction in its own Event Graph. |
| 02. Two hands | BP_TwoHandRifle, BP_TwoHandBinoculars |
The rifle uses Grip_Main/Grip_Support on the mesh; the binoculars use two component anchors without a socket. |
| 03. Assembly inspection | BP_ScalableEngine, BP_RemovablePiston |
Two hands scale and rotate the engine; PistonSeat accepts a released piston with the tag Interaction.EnginePiston. |
| 04. Spatial panel | BP_SpatialPanel |
Resize the frame with the hands, press TEST POINTER with a separate pointer. WorldControls is attached to the mesh and scales with the frame. |
| 05. Bow | BP_Bow, BP_Arrow |
Hold the bow and arrow in different hands, nock the arrow, draw and release. UpperString and LowerString are visible even without an arrow. The bow's Event Tick updates both sections by the draw of BowInteraction; OnShot → Launch launches the arrow. |
| 06. Bunker | BP_BunkerWheel, BP_BunkerDoor |
Take the rim of the red three-spoke wheel and make two full turns. The wheel's Event Graph checks the travel. The door smoothly rotates 100° around the side hinge, and the wheel moves with the leaf. |
| 07. Strike | BP_TwoHandAxe, BP_ChoppingLog |
Take the axe with two hands and hit the log with the blade. OnStrike on the server calls the event SplitNow, which sets the replicated bSplit; the function OnRep_bSplit hides the intact log and shows the two prepared halves on all machines. |
The RESET ALL DEMONSTRATIONS button on the panel, Home in the emulator or B on Quest Touch first release active grips on the server. Then BP_VRLabPawn.OnLabResetRequested runs a server travel back to VRLabBP: the door, log, button and all items return to their initial state.
Open BP_Bow, BP_BunkerWheel, BP_BunkerDoor, BP_TwoHandAxe, BP_ChoppingLog, BP_UseButton and BP_VRLabPawn to view their Event Graphs.
BP_ChoppingLog is a model of how to make a state visible to everyone in Blueprint. The strike event runs only on the server, so you cannot change meshes directly in it: other players would not see it. Instead the variable bSplit has Replication = RepNotify, and the whole visual change lives in the function OnRep_bSplit. The server calls it itself after Set w/ Notify, clients when they receive the new value, including a player who joined after the strike.
In plain words. The server does not draw the split log for everyone — it only announces "the log is split". Every machine, hearing the announcement, hides the intact log and shows the halves itself.
The other items show composition from UInteractionManipulationComponent, UInteractionGripPointComponent, UInteractionDockComponent, profiles and ordinary Blueprint properties. Grabbing, network ownership, physics and the two-hand solver remain the implementation of the reusable Core/World modules. BP_VRLabPawn and BP_VRLabGameMode are Blueprint assets; for XR input, the desktop emulator and station transitions the pawn inherits the ready-made AInteractionVRPawn. The spatial widget uses UInteractionVRPanelWidget from the Demo module. So the examples of item behavior can be studied and changed in Blueprint without rewriting the low-level XR input.
All 16 Blueprint assets, the map and the materials are part of the plugin. Open a Blueprint in the editor to view or change the graphs and component settings; no extra scripts are needed to run. For Quest 2 check your own Android build and the behavior on the headset.