VR Hand Component

Description

VR Hand Component represents the player's hand in a VR environment. It utilizes physics for realistic interactions and employs physics constraints to achieve accurate physics-based behavior. The class is derived from UVR_MotionControllerComponent.

Main Features

• Physics Interactions

• Finger Collision

• Weapon Interactions

• Equipment Interactions

• Finger IK (Inverse Kinematics)

• Hand Animations

• Menu Functionality

• Radial Inventory Support

• Pull Grab Functionality (Gravity Pull and Direct Pull)

Getting Started Guide

Creating the VR Hand Component Blueprint 🎨

You have two options to set up the VR Hand Component:

Option 1: Create a New Blueprint

• Create Blueprint: Create a new Blueprint derived from UVR_HandComponent.

• Setup: Configure the component from scratch according to your project's needs.

Option 2: Use the Existing Blueprint

• Use Existing: Utilize the preconfigured Blueprint provided in the Demo Content folder.

• Benefit: This Blueprint is already set up for easy integration and can be customized further.

  
  

  

  
  

Adding the VR Hand Component to Your Actor

• Add Component: In your VR Player class/BP , select the UVR_HandComponent class/BP.

Customization and Setup

Visual Customization 🎨

Customize the appearance of the VR hand and related elements under the Visualization category:

• Hand Mesh: Assign a skeletal mesh for the hand (e.g., SK_VR_Robot_Hand or your custom hand model).

• Hand Collision Mesh: Set up a collision mesh for precise interactions.

• Teleport Cylinder Mesh: Customize the visual indicator for teleportation destinations.

• Teleport Arrow Mesh: Change the appearance of the teleport direction arrow.

• Menu Cursor Mesh: Customize the cursor used during menu interactions.

• Room Scale Mesh: Adjust the visualization of room-scale boundaries.

Animation and Finger IK Setup 🎬

Achieve realistic hand and finger movements by setting up animations and IK:

Step 1: Select Animation Blueprints

• Assign Blueprints: Assign animation Blueprints to RealHandMesh and FakeHandMesh.

• Requirement: These Blueprints should be derived from UVR_HandAnimationInstance.

  

Step 2: Choose Open and Closed Hand Animations

• Open Hand Animation: Assign an animation for the open hand pose (a stretched hand works best).

• Closed Hand Animation: Assign an animation for the closed fist pose.

• Purpose: These animations are essential for natural grabbing and releasing actions.

Step 3: Set Tip Sockets for Each Finger

• Assign Sockets: Under Tip Sockets, assign the socket names for each fingertip based on your hand skeleton.

• Precision: This enables precise finger movement and collision detection.

  

Step 4: Adjust Finger IK Settings

• NumSamplePoints: Specify the number of segments or traces for each finger to control bending smoothness.

• IkTraceCapsuleRadius: Set the trace capsule radius for IK calculations.

Step 5: Run Finger IK Setup

• Automate IK: Use the RunFingerIKSetUp button or change any setting to automate the finger IK setup process.

Finger Collision Setup 🛡️

Enhance interaction accuracy with proper finger collision setup:

Step 1: Specify Hand Collision Mesh

• Set Collision Mesh: Assign the collision mesh for the hand to enable precise environmental interactions.

  

Step 2: Place Tip/Start Sockets

• Position Sockets: Place the FingerStart and FingerTip scene components at the base and tip of each finger on the hand skeleton.

• Components:

  • ThumbFingerStart and ThumbFingerTip

  • IndexFingerStart and IndexFingerTip

  • MiddleFingerStart and MiddleFingerTip

  • RingFingerStart and RingFingerTip

  • PinkyFingerStart and PinkyFingerTip

    

  
  

Hand Physics and Constraints Configuration ⚙️

Configure physics settings to simulate realistic hand behavior:

Physics Constraints Overview

• HandPhysicsConstraintInstance: Active when the hand is colliding; connects FakeHandMesh and PhysicsHandSocket.

• HandPhysicsConstraintPDInstance: Active when the hand is not colliding; provides smoother movement.

• PickPhysicsConstraintInstance: Manages object grabbing mechanics.

Constraint Parameters

• LinearForceLimit and AngularForceLimit: Control the maximum forces applied to the hand.

• LinearPositionStrength and AngularPositionStrength: Adjust the strength of position constraints.

• LinearVelocityStrength and AngularVelocityStrength: Control the responsiveness of hand movements.

• Interpolation Speeds:

  • LinearPositionInterpSpeed

  • LinearVelocityInterpSpeed

Drag Curve

• Assign DragCurve: In the Physics settings, assign a DragCurve to manage constraint behavior based on the distance between the hand and controller.

• Note: A curve is necessary.

  

Pull Grab Functionality 🧲

Enable the ability to pull distant objects toward the hand:

Step 1: Enable Pull Grab

• Activate: Set bCanPullGrab to true to enable pull grabbing.

Step 2: Select Pull Grab Type

• Options:

  • Gravity Pull: Objects are smoothly pulled toward the hand (similar to Half-Life: Alyx).

  • Direct Pull: Objects move directly to the hand's location (similar to Boneworks).

Step 3: Configure Pull Parameters

• PullGrabDistance: Maximum distance to initiate a pull grab.

• PullCheckDelay: Interval between pull grab checks.

• DirectPullGrabDistance: Specific distance setting for direct pulls.

• DirectPullCurve: Assign a curve for smoothing direct pulls.

  

Inventory and Menu Setup 📋

Integrate menu systems and radial inventory support:

Menu Settings

• Enable Menu: Set bTurnOnSpawnableHandMenu to true to activate menu functionality.

• Assign Classes:

  • MainMenuClass: Assign the class to use for the main menu.

  • PauseMenuClass: Assign the class to use for the pause menu.

• MenuLoadingWidgetClass: Assign a widget class for the loading indicator when accessing menus.

• MenuGrabAnimation: Optionally specify an animation for menu interactions.

Radial Inventory

• CA_Inventory Component: Use the CA_Inventory (UChildActorComponent) to manage the hand's radial inventory.

• Activation: Press the thumbstick button on the right controller to access the radial inventory.

• Setup: Assign the appropriate class to CA_Inventory and configure inventory items as needed.

Component Hierarchy and Descriptions

Hierarchical Structure

• RootScene (USceneComponent)

  • The root component of the hand, serving as the base for all other components.

• Hands (USceneComponent)

  • Contains all hand-related components.

  • HandSocket (USphereComponent)

    • Serves as a socket for the non-physical hand mesh.

    • FakeHandMesh (USkeletalMeshComponent)

      • A non-physical skeletal mesh representing the hand when not interacting with physics objects.

      • ArcNiagara (UNiagaraComponent)

        • Used for teleportation arcs.

      • WidgetInteractionComponent (UWidgetInteractionComponent)

        • Facilitates interaction with UI widgets.

  • PhysicsHandSocket (USphereComponent)

    • Serves as a socket for the physical hand mesh and simulates physics.

    • RealHandMesh (USkeletalMeshComponent)

      • The physical hand mesh that interacts with physics objects.

      • Finger Collisions (UCapsuleComponent)

        • ThumbFingerCollision

        • IndexFingerCollision

        • MiddleFingerCollision

        • RingFingerCollision

        • PinkyFingerCollision

      • Finger Scene Components (USceneComponent)

        • Start and tip components for each finger (e.g., ThumbFingerStart, ThumbFingerTip).

      • GrabRoot (USceneComponent)

        • Base component for grabbing functionality.

        • GrabDirection (UArrowComponent)

        • Indicates the direction for grabbing actions.

      • CA_Inventory (UChildActorComponent)

        • Manages the hand's radial inventory.

      • MenuWristLoader (UWidgetComponent)

        • Displays the menu loading bar.

      • RealHandCollision (UStaticMeshComponent)

        • Provides collision for the physical hand mesh.

• ArcDirection (UArrowComponent)

  • Determines the direction of the teleportation arc.

• PullDirection (UArrowComponent)

  • Indicates the direction for pull grabbing.

• ArcEndPoint (UStaticMeshComponent)

  • Represents the end point of the teleportation arc.

• MenuCursor (UStaticMeshComponent)

  • Displays the cursor during menu interactions.

• TeleportCylinder (UStaticMeshComponent)

  • Visualizes the teleportation destination area.

  • Arrow (UStaticMeshComponent)

    • Shows the teleportation direction.

    • RoomScaleMeshComponent (UStaticMeshComponent)

      • Outlines the room-scale boundaries.

• WidgetSphereMesh (UStaticMeshComponent)

  • Used for widget interactions.

• PullVisualizer (USceneComponent)

  • Visualizes the pull grab effect.

• DirectPullTimeLine (UTimelineComponent)

  • Manages the timing for direct pull animations.

Tick Algorithm Overview

The VR Hand Component performs various functions each frame to ensure smooth interactions:

• HandPhysicsTick

  • Manages physics constraints based on collision status.

  • Switches between HandPhysicsConstraintInstance and HandPhysicsConstraintPDInstance.

• CheckAimToGrab

  • Moves the hand closer to nearby grabbable objects using physics constraints.

• UpdateHandAnimation

  • Updates hand animations based on input and interactions.

  • Adjusts finger poses using IK.

• UpdateRoomScaleOutline

  • Adjusts the room-scale boundary visualization relative to the teleport destination.

• CheckMenuStatus

  • Manages menu activation and adjusts hand visibility and functionality accordingly.

• UpdateWidgetCursor

  • Moves the cursor on UI widgets during interactions.

• CheckHandsAndControllerDist

  • Ensures the hand stays within a reasonable distance from the controller.

  • Adjusts physics constraints if necessary.

• CheckControllerAndPickDist

  • Drops held objects if they are too far from the controller.

• CheckGrabPossibility

  • Verifies if grabbing is possible based on object weight, distance, and player input.

• CheckMenuButtonPress

  • Monitors the duration of menu button presses to trigger menu actions.

• UpdateAllFingersCollision

  • Recalculates finger collisions based on the current hand pose.

• MakeUpdateWidgetLookAtCamera

  • Keeps the menu or UI widget facing the player.

The VR Hand Component uses three physics constraints managed via FConstraintInstance:

• HandPhysicsConstraintInstance: Connects the FakeHandMesh and PhysicsHandSocket when the hand is colliding.

• HandPhysicsConstraintPDInstance: Used when the hand is not colliding.

• PickPhysicsConstraintInstance: Manages object grabbing mechanics.

These constraints are dynamically switched in HandPhysicsTick based on the hand's collision status. All relevant components have "Simulation Generates Hit Events" enabled for proper functionality.

Hand Skeleton

• Skeleton Compatibility: Supports both SteamVR and Unreal Engine XR skeletons.

• Settings:

  • Reflect Left Hand: Mirrors the hand model for the left hand.

  • Using Steam VR Skeleton: Enables compatibility with SteamVR skeleton.

• Finger Bones: Configurable bone names for each finger to ensure accurate finger collision and IK.

Finger Collision(UE 4.27)

Finger collision are using physics blend(works with SteamVR skeleton only). Requires skeletal physics asset set up(See demo skeletal physics asset example).

Line traces for Grab IK(Technical info)

Hand uses line traces for each finger. Each finger rotation value is from 0 to 1 so the value of each line trace is 1/NumberOfTraces(4)=0.25 (Trace 1: 0-0.25, Trace 2: 0.25-0.5, Trace 3: 0.5-0.75 and Trace 3: 0.75-1).

Menu settings

Menu(Actor attached to the FakeHandMesh) can be spawned after holding A button on the left controller(Loading ring will apear while holding the button). Main Menu class and Pause Menu class is classes which will be spawned in certain conditions(Main Menu if Player has true at Menu Status and Pause Menu if player pressed the button). Menu grab animation can be specified.(Do not to forget to select the classes otherwise project will crash)

Hand radial inventory

CA_Inventory(Child Actor Component) is a inventory actor which can be spawned by pressing the thumbstick button on the rightcontroller(Class should be selected at least with 0 values to avoid issues. See VR Hand Inventory for more information).

Other Settings

Ammo Clips - This is an array of classes in which the information of ammo classes is stored. Index is a caliber type which is get from Player(See VR Player). This variable is used in the grabbing function. If hand is in the ammo box and player has some ammo it will spawn the actor of the class from that array by a caliber(Index).

Hit Surface Haptic Effect - This is a Haptic Effect which is playing when hand hit the surface.

Teleport - Variables which effect the teleport.

Grab - Variables which effect the teleport(Speed, Sound etc.).