2023 Unity VR Basics - Grabbing Objects

Summary

This video tutorial delves into the mechanics of object grabbing in virtual reality (VR) using Unity's XR Interaction Toolkit. It covers the essentials of setting up XR Direct Interactors on VR controllers and configuring them with colliders for interaction. The video also explains how to create XR Grab Interactables for objects, ensuring they have the necessary Rigidbody and collider components. Further, it explores various interaction modes, movement types, and the use of Attach Transforms for precise object handling. The tutorial concludes with a discussion on interactable events, including audio and haptic feedback, to enhance user immersion in VR experiences.

Takeaways

• 🎯 To grab objects in VR, utilize the XR Grab Interactable and XR Direct Interactor components.
• 📦 Adding an XR Direct Interactor to a controller requires a collider, such as a Sphere Collider set to 'Is Trigger' for functionality.
• 🔍 The Interaction Manager handles the interaction between the interactor (hand) and interactables (grabbable objects).
• 🎭 The Interaction Layer Mask allows for selective interaction, separating UI components from grabbable objects.
• 🖐️ Select Action Trigger determines how selection starts, with options like 'States Change', 'State', 'Toggle', and 'Sticky'.
• 👀 Hide Controller on Select can be used to improve visual aesthetics during object interaction.
• 🔨 XR Grab Interactables require a Rigidbody and a collider to function properly.
• 📏 Collision Detection can be set to 'Continuous Dynamic' to prevent objects from passing through the ground at high speeds.
• 🔄 Movement Types for grab interactables include Kinematic, Instantaneous, and Velocity Tracking, each with different behaviors.
• 🎚 Attach Transform allows for precise control over where and how objects attach to the hand during interaction.

Q & A

What are the two components required for grabbing objects in VR as discussed in the script?

The two components required for grabbing objects in VR are the XR Grab Interactable and the XR Direct Interactor.

Why is a collider necessary for the XR Direct Interactor to function?

A collider, specifically set as a trigger, is necessary for the XR Direct Interactor to function because it acts as a trigger for interaction, allowing the VR system to detect when the user's hand is near an object that can be grabbed.

What is the purpose of the Interaction Manager within the XR Direct Interactor?

The Interaction Manager within the XR Direct Interactor is responsible for handling the interaction between the interactor (the user's hand) and the interactable objects that can be picked up.

How does the Interaction Layer Mask in the XR Direct Interactor work?

The Interaction Layer Mask in the XR Direct Interactor allows the developer to specify which layers the interactor should interact with. This can be used to separate interactions, such as only allowing UI components to interact with other UI elements and not with the grabbable objects.

What are the different select action triggers available in the XR Direct Interactor?

The different select action triggers available in the XR Direct Interactor are States Change, State, Toggle, and Sticky. Each offers a different method of how the selection and grabbing of objects are initiated and maintained.

Why might someone choose to hide the controller on select?

Hiding the controller on select is chosen to improve the visual realism of the VR experience, as it prevents the user's hand model from visibly passing through objects during interaction, which can be visually jarring.

What is an XR Grab Interactable and why is it necessary for grabbing objects in VR?

An XR Grab Interactable is a component that must be added to objects in the VR scene to make them grabbable. It is necessary because it allows the XR system to recognize these objects as interactable and respond to the user's grabbing actions.

Why does the XR Grab Interactable require a Rigidbody component?

The XR Grab Interactable requires a Rigidbody component because it allows the object to have physical properties that can be manipulated by the user, such as mass and the ability to interact with other objects through collisions.

What are the different movement types available for XR Grab Interactables?

The different movement types available for XR Grab Interactables are Kinematic, Instantaneous, and Velocity Tracking. Each type affects how the object moves and interacts with the user's hand and other objects in the VR environment.

How does the Attach Transform feature work in the XR Grab Interactable?

The Attach Transform feature in the XR Grab Interactable allows the developer to specify an exact point on the object where it should attach to the user's hand when grabbed. This ensures that the object's orientation and position are correct relative to the hand.

What are Interactable Events and how can they be used in VR development?

Interactable Events are triggers that occur when the interactor comes into contact with an interactable object, such as hovering over it or selecting it. They can be used to create interactive feedback, like changing the object's appearance or activating abilities, to enhance the user's experience.

Outlines

00:00

🤲 Introduction to VR Object Grabbing

The video begins with an introduction to grabbing objects in virtual reality (VR), focusing on the use of two key components: the XR Grab Interactable and the XR Direct Interactor. The presenter aims to cover the topic efficiently and starts by setting up the project with the XR origin and hand controllers. The XR Direct Interactor is added to the controllers, and it's explained that a collider, specifically a sphere collider set to trigger, is necessary for the interactor to function. The presenter adjusts the collider's size for a more accurate hand interaction, and the process is repeated for the left hand. The video then delves into the components of the XR Direct Interactor, such as the interaction manager, interaction layer mask, and different select action triggers like state changes, state, toggle, and sticky. The presenter also discusses the option to hide the controller on select and the starting selected interactable feature, which allows objects to be pre-grasped at the scene's start.

05:00

🔨 Setting Up Grab Interactables

The second paragraph continues the tutorial by demonstrating how to create grabbable objects in VR. The presenter adds a 3D cube to the scene and attaches an XR Grab Interactable component to it, emphasizing that a Rigidbody is mandatory for the component to work. The Rigidbody's collision detection is set to 'Continuous Dynamic' to prevent objects from passing through the ground at high speeds. The presenter then adjusts the interaction layer mask to ensure the grab interactable only interacts with the correct layer. Various select modes are introduced, with a focus on the single select mode for this tutorial. The gaze configuration is mentioned but not covered due to the lack of eye-tracking hardware. The presenter also discusses movement types, such as kinematic, instantaneous, and velocity tracking, and their effects on object interaction. The concept of an attach transform is introduced, which allows for precise control over where and how objects attach to the hand controller in VR.

10:02

🎮 Interactable Events and Conclusion

In the final paragraph, the presenter explores interactable events, which are triggered when the interactor comes into contact with an interactable object, such as hovering or selecting it. These events can be used to create visual cues for the player, like changing the object's mesh when it's hover over. The presenter also touches on the audio and haptic events available in the XR Direct Interactor, which can enhance immersion by providing auditory and tactile feedback when objects are interacted with. The tutorial concludes with a reminder to support the content creator, either through Patreon or simply by liking the video, and a tease for future content that will perfect the throwing mechanics in VR.

Keywords

💡XR Grab Interactable

The 'XR Grab Interactable' refers to a component in virtual reality (VR) development that allows objects to be recognized as grabbable by the XR system. In the context of the video, this component is essential for enabling users to interact with objects within a VR environment. The script mentions adding this component to a 3D cube to make it grabbable, illustrating how it plays a central role in creating immersive VR experiences.

💡XR Direct Interactor

The 'XR Direct Interactor' is a component used in VR development to handle direct interactions with objects, such as grabbing. It requires a collider, typically a sphere collider set to trigger, to function properly. The video script describes adding this component to VR hand controllers, emphasizing its necessity for detecting and responding to user actions like grabbing objects within the VR space.

💡Collider

A 'Collider' in VR development is a component that detects and responds to collisions between objects. The video script specifically mentions the need for a sphere collider set to 'is trigger' for the XR Direct Interactor to work. This component is crucial for creating realistic interactions, as it enables the system to recognize when a user's hand (controller) comes into contact with an object that can be grabbed.

💡Interaction Manager

The 'Interaction Manager' is a component that oversees the interactions between interactors (like hands) and interactables (like grabbable objects) in a VR environment. The video script discusses this component in the context of the XR Direct Interactor, highlighting its role in managing how users interact with objects in VR. It's a key part of creating a seamless and intuitive user experience.

💡Interaction Layer Mask

The 'Interaction Layer Mask' is a feature that allows developers to specify which layers or groups of objects can interact with each other in a VR scene. The video script explains how to set this mask to limit interactions to only those objects on the 'interactable' layer, ensuring that UI components, for example, only interact with other UI elements and not with grabbable objects.

💡Select Action Trigger

The 'Select Action Trigger' determines how an object is selected or activated in VR. The video script outlines different selection modes such as 'States Change', 'State', 'Toggle', and 'Sticky', each offering different user interaction experiences. For instance, 'States Change' requires the grip button to be pressed to grab an object, while 'State' allows objects to be picked up just by touching them while holding the grip button.

💡Hide Controller on Select

The 'Hide Controller on Select' option is a feature that allows the VR system to hide the controller's visual representation when an object is selected. This can improve the visual realism of the VR experience, as demonstrated in the video script, where hiding the controller can prevent visual inconsistencies when objects are grabbed, especially if there's no custom animation for grabbing.

💡Starting Selected Interactable

The 'Starting Selected Interactable' is a setting that allows an object to be pre-selected or 'held' by the user at the start of a VR scene. The video script mentions this feature in the context of initializing a player with a specific object, like a gun, at the beginning of a game. This can be used to streamline the start of a VR experience by having necessary tools or items ready for immediate use.

💡Attach Transform

The 'Attach Transform' is a component that specifies where an object should attach to the hand controller when grabbed. The video script provides an example of creating an 'attach point' for an object, ensuring that when picked up, the object's orientation and position relative to the hand are correct. This is crucial for creating natural and intuitive object interactions in VR.

💡Interactable Events

Interactable events are triggers or actions that occur when an interactor comes into contact with an interactable object. The video script discusses using these events to change the mesh of an object when hovered over, indicating to the player that it is interactable. These events are part of creating a responsive and dynamic VR environment that provides feedback to the user's actions.

Highlights

Introduction to grabbing objects in VR using XR Grab Interactable and XR Direct Interactor components.

Adding XR Direct Interactor to the controllers with a sphere collider set as a trigger.

Adjusting the collider size for a more precise interaction with objects.

Setting up the Interaction Manager and Interaction Layer Mask for object interaction.

Explanation of different select action triggers like States Change, State, Toggle, and Sticky.

Option to hide the controller on select for a more realistic grabbing experience.

Creating grab interactables by adding the XR Grab Interactable component to objects.

Requirement of a Rigidbody and collider for XR Grab Interactables to function properly.

Setting the Collision Detection mode to Continuous Dynamic for more accurate interactions.

Configuring the Select Mode for single or multiple hand grabbing.

Discussing movement types like Kinematic, Instantaneous, and Velocity Tracking.

Creating an Attach Transform for precise object attachment to the hand.

Adjusting the Attach Transform's rotation to match the hand's orientation.

Using Interactable Events to trigger actions like changing mesh or activating items.

Incorporating Audio and Haptic Events to enhance user interaction and immersion.

Practical demonstration of grabbing objects in a VR scene with the configured settings.

Encouragement for Patreon support and appreciation for viewers.

Transcripts

let's talk about grabbing objects in VR

and in order to grab things we're going

to need to know how to use two

components that being the XR grab

interactable and the XR direct

interactor as always I want to cover as

much as possible in the smallest amount

of time so let's get started opening up

the project you'll see here I haven't

really added anything new I do have this

new object here that I'll go over later

in the video but yeah we have the XR

origin and then we have our left and

right hand controllers let's kick things

off by adding a XR direct interact to do

that all we have to do is Select our two

controllers here and I'm going to type

in XR direct interactor and there we go

we have the XR director interactor but

it's also going to need some form of

collider that's going to act as a

trigger without that this will not work

so I'm going to add a sphere collider

and expand this out I'm going to set it

to is trigger and then we have a pretty

big radius here so we need to reduce it

down and you know I'm just going to grab

the hand model for a reference let's see

where is my yeah let's go with the right

hand and I'll just drag this into the

scene make sure it's zeroed out

all right and so I'm going to take this

radius and reduce it I'm going to try

point one and you see that is just about

the right size you know you could try

something like

.08 if you want it to be a little more

exact for when your hand interacts with

an object and then we just have to make

sure that we do this for the left hand

as well yeah you know I like .08 a

little better and then I'm just going to

get rid of this reference so with that

let's go over the director interactor

looking through some of these components

you can see we have an interaction

manager so that is going to be handling

the interaction between our interactor

which is going to be our hand and then

the interactable which will be the

objects that we can pick up next we have

an interaction layer mask so we might

not want to interact with every single

object in the scene sometimes you want

your UI components to just interact with

UI components and so this is where we

would add a layer to separate these

interactions and you just click add

layer and we could add one here called

the interactable

coming back to our hands so you know I

could say uh I don't want this to

interact with anything I only want

things to interact with the interactable

layer and then down here we have an

attached transform so if you do not have

anything here and this is set to none

it's just going to use the transform of

the XR direct interactor which I'm okay

with right now we also have select

action trigger so this would determine

how our select starts so it's kind of

interesting so States change is how you

would expect you know you go down you

grab an object and then when you pick it

up you know you're holding the grip

button but when you release it it drops

the other ones we have is state so how

State works is when you go in and you

are holding the button even if you are

not interacting with the object if you

ran into it while holding the grip

button it would pick it up which is kind

of a weird interaction but there it is

we also have toggle and sticky and

toggle and sticky are very similar in

the sense that you would be hovering

over a object and when it's togg you can

press the grip button or whatever your

activation button is and then when you

release it it'll still stay on you but

when you press it again then it will

release and how sticky works is the same

way but it only lets go of the object

when you let go for this second time so

yeah there you go a few options on how

you can pick up your objects we also

have hide controller on select and you

know I'm going to select both my left

and right hand controller and I'm just

going to check that so if you don't have

a custom animation or dynamic grabbing

for your objects it kind of looks a

little wonky the hand will go right

through the object and personally I like

to hide the controller on select but you

know actually for demonstration purposes

later I'm going to check this off for

now we also have the odd choice right

here of starting selected interactable

so if we boot up the scene and head

something here if we had something that

was a XR grab interactable then this

would just start off in our hand at the

beginning of the scene so say you want

the player just to have a gun in their

hand at the beginning this is where you

could put that and finally we have a

bunch of events here audio events haptic

events in interactor events that we can

use when we pick up our objects but we

don't have any objects to pick up so

let's fix that now in order to grab

things we need grab interactables and

well just objects to grab them so I am

going to activate this and show you what

I've done here and as you can see I'm

actually going to hide these for now all

I have here is a table and the table is

just comprised of a cube that I made I

put a 0.5 position and scale of one and

yeah this is just a simple little table

so we can grab onto things and you'll

see the XR origin is right here so when

we start up the scene we'll be looking

at this table and be able to grab things

off it and well let's make a grab

interactable so to do that we need to

right click grab a 3D cube I am going to

reduce this to let's see 0.2 might be a

good size yeah just for now and there we

go next we need to add a well grab

interactable component to it so I'm

going to come over here add X our grab

interactable and one thing I want to

point out is you'll notice that it added

a rigid body right here XR grab

interactables will not work without a

rigid body you kind of like how our

hands will not work without a sphere

collider set to trigger or any collider

set to trigger we need to have a rigid

body on our XR grab interactables and

also some form of collider as well one

thing I'll point out about the rigid

body is you might want to up the

Collision detection so I'm going to set

this to continuous Dynamic and this is

going to be a little more expensive than

doing something like discrete or

continuous but it does help prevent

objects from flying through the ground

when they're going at higher speeds if

you're ever having those problems where

the colliders aren't really picking

things up you might want to consider

continuous Dynamic expanding this out

let's go over some things for the grab

interact you'll see here that it has the

interaction manager from before the one

that is responsible for handling our

interactions between our interactables

and interact doors we also have the

interaction layer mask and this is set

to default and if you remember just a

second ago I set this to only

interactable so we need to make sure

that this is set to the proper one so

I'm going to oh where is it there we go

and there we go I'm going to set it to

interactable take it off default we also

have different types of Select mode so

there is single and multiple just for

this one I'm just going to cover single

we'll cover multiple hand grabbing

objects later we have a gaze

configuration which well I can't afford

the Oculus Pro or any other eye tracking

device so I can't cover it sorry but hey

I do have a patreon if you want to help

me out with that patreon plug seriously

though just a like would be enough if

you're finding this video helpful but

yeah all right let's move on uh we also

have different movement types I will

cover this in a second we also can

determine if we want the object to track

or not so if we don't want it to track

let's say the position we could turn

that off here or if you want the rate

rotation of the object to be maintained

so even though we're turning our

controllers then if we turn this off it

wouldn't turn with it it just moves the

position we can also decide to smooth

this out and so this kind of gives you a

bit of a floaty feel that you can play

with same with the road rotation we also

have a ton of options when it comes to

throwing and so we can determine if we

want to throw on detach or just drop it

immediately and not track the velocity

and we can play with this later I'm

going to try to make a video that

perfects throwing because well for the

game Jam I made a game where you

primarily throw things and God did I

hate my throwing but right and then we

have attached transforms where we can

specifically say where I pick up an

object I want you to attach exactly at

this location and I will cover that in

just one second now I know I keep saying

one second and that one second has

passed so let's cover what the movement

types are so I'm going to go ahead and

click this off

and I'm going to activate these three

cubes and as you can see here there's

nothing crazy going on I've just put a

little canvas on these to symbolize what

these are going to stand for and so what

we have here is a cube with kinematic

instantaneous and velocity tracking

movement and if I start up the scene

you'll see when I grab the instantaneous

Cube it moves instantly with my hand but

when I push it through the table it goes

right through and that's because it

disables the rigid body on it and the

same with the kinematic but the

kinematic has kind of a bit of a

floatiness to it it lags behind but

still goes through the table and finally

we have velocity tracking which has that

lagging but also stops when you try to

push it through the table and yeah that

is all of them boopping back to the

project I think it's important to

mention the attach transform and how

this essentially works is we'd have to

create an empty object here I'm going to

call it attach transform or actually

even better since this one's a little

long I'm going to choose the velocity

tracking one

you know I'm gonna go with attach point

I like that name better and so if we see

here this is going to be zeroed out on

our velocity tracking object and what we

want to keep in mind is we want to make

sure that this is set to local

in that the rotation is correct here and

what I mean by that is the x-axis this

red axis should be pointed towards the

palm of our hand the y-axis should be

pointed towards where we consider the

top and then the Z should be pointed

forwards now for this example let's say

I want the top of this surface to be

pointing forwards I want the V to be

pointing upwards and then I want this to

be pointing towards my palm so I would

switch to rotation and I would adjust

those accordingly

oop my bad I have the wrong thing

selected it's the attach point that we

need to rotate

all right so now we have the y-axis that

is pointing upwards and so my V should

be pointing upwards and then the x is

pointed towards my palm and then this

should be pointing forwards when I pick

it up now the last thing I need to make

sure I do is make sure that I set the

attach point so I'm going to come over

here I'm going to drag that there and

then let's boot up the scene now as you

see when I pick it up the V points

upward because the Y position was there

the X points towards the palm of my hand

and the Z points forward next we need to

look at interactable events and so these

are events where well if you imagine the

interact door comes in contact with our

interactable so that could be it

hovering that could be it selecting it

or deselecting it and we can use these

to do things like when we hover over it

maybe change the mesh so the player

knows that the object is interactable

and we could also do things like when we

select it maybe you want to make that

item active so maybe it turns on a

shield for the player and then you know

if we go over to the XR direct interact

tour we also have the same kind of

events that we can play with but even

more so we have these events so we have

audio events that we can trigger in

haptic events so on select entered you

might want to add in an audio clip and

play a sound for the player or when we

come over here we might want to do

haptic events this is really important

for immersion so again when they're

selecting when you grab something in

real life you kind of have a tactile

response and this little vibration and

duration that you can add here is going

to let the player know that okay they've

grabbed something and based on if it's a

heavier object maybe you want it to have

a very intense haptic feedback now when

it comes to interacting with objects you

know the basics of it as always I love

you my patreon members and I hope you

found this useful and I'll see you in

the next one bye

[Music]