VR Basics. Virtual Reality /23/2018

Transcription

1 VR Basics Reference: Virtual Reality Technology and Applications & Stanford VR Course Virtual Reality 101 Virtual Reality An interactive computer simulation that senses the user s state and replaces / augments sensory feedback to one of more senses in such a way as to immerse them within the virtual environment. Four basic elements: 1. Virtual Environment 2. Virtual Presence 3. Sensory Feedback 4. Interactivity 1

2 Virtual Reality 101 Virtual Environment descriptions of objects within the simulation and the rules / relationships that govern the objects Displayed through visual, aural, haptic devices and perceived through vision, hearing and touch, etc Environment Topology areas and features Objects things that occupy space Intermediaries avatars / controlled by players User Interface Elements interface elements such as buttons, switches sliders Virtual Reality 101 Virtual Presence The feeling of being in the environment Physical Presence performed by using synthetic stimuli that affect the user s senses Mental Presence engagement, expectations, the feeling of being part of the world Telepresence the feeling of virtual presence in a distant location Absence the idea of removing oneself from the environment / ignoring the environment. To immerse yourself in a book you must detach from the environment around you. 2

3 Virtual Reality 101 Physical (sensory) Virtual Presence Virtual Reality 101 Physical (sensory) Virtual Presence 3

4 Virtual Reality 101 Sensory Feedback Most feedback is visual Usually, at minimum, requires tracking the user s position and orientation ART Hand Tracking System _channel=virtalis Virtual Reality 101 Interactivity - Respond to the user s actions Ability to affect the environment Update the location / view (move around) Perspective First Person looking through the eyes of an avatar Second Person Looking from the immediate vicinity of relevant activity (maybe the arm of a robot) Third Person viewing from an independent location 4

5 Virtual Reality History Stereoscopes 1931 Brave New World discussed movies called feelies that added touch to motion pictures 1957 Sensorama - virtual bicycle ride featuring moving displays, wind and vibration (first VR) Virtual Reality History 1957 Sensorama - virtual bicycle ride featuring moving displays, wind and vibration (first VR) 5

6 Virtual Reality History 1968 Sword of Damocles superimposed wireframe images over the environment (first AR) Virtual Reality History 1970s Videoplace allowed for interaction for artists 1987 VR on cover of Scientific America & Star Trek TNG Holodeck 1990s CAVE (Cave Automatic Virtual Environment) where walls are screens 6

7 Virtual Reality History 1995 Nintendo Virtual Boy Oculus Rift, HTC Vive, Explosion of VR and AR devices from major companies and startups Virtual Reality Applications Flight and Driving Simulations Ku1ZEFBJY&ab_channel=BigReviewTV Surgery Simulators Design / Visualization el=emulate3d- IndustrialControlsTesting%2CSimulationandDemonstration 7

8 Mixed Reality Mixed Reality 8

9 Modeling & Simulation Resiliency against superstorms Visualize events for public education Explain scenarios Modeling & Simulation 9

10 Medical Mixed Reality Mixed Reality encompasses all types of reality, from real to virtual Augmented Reality refers to virtual objects being merged with reality The lesser known Augmented Virtuality consists of real world objects merging with the virtual world 10

11 Mixed Reality The lesser known Augmented Virtuality consists of real world objects merging with the virtual world Here we see my son using a 3D printed T-Rex Jaw bone to try and complete the virtual skeleton Virtual Reality System 11

12 Virtual Reality System Human Visual System Light passes through the cornea, which protects the eye Passes through the pupil, the hole in the iris Light passes through a flexible lens to redirect rays of light Light passes through the vitreous humor, a gelatinous substance in the eye and strikes the fovea The photoreceptors on the retina are in central vision 12

13 Human Visual System Two types of photoreceptors: Rods Brightness Cones Color Photoreceptors are transmitted via the optic nerve and the optic chasm, the lateral geniculate nucleus, occipital cortex and visual cortex Depth Cues Monocular depth cues, stronger than binocular cues 2D Lighting & Shadows close is bright, far is dim Perspective smaller the further they are Size of known objects size expectations Detail more detail in close objects Occlusion blocking objects are in front Relative Motion far away things move slowly 13

14 Depth Cues Lighting & Shadows influences the orientation and distance between lights and objects Depth Cues Occlusion/Interposition when objects partial hide one another the hidden object is interpreted as further away 14

15 Depth Cues Relative Size objects of the same type that get smaller appear further away Depth Cues Detail more detail in close objects 15

16 Depth Cues Perspective smaller the further they are, two types: Oblique Perspective edges parallel Linear Perspective has a vanishing point Depth Cues Variation in Visibility Fog, particles suspended in air 16

17 Depth Cues Motion Parallax objects close move faster than objects further away Depth Cues Motion Parallax objects close move faster than objects further away 17

18 Depth Cues Proprioceptive Cues information from joints and muscles though the nervous system Accommodation muscles that shape the lens and the sharpness of the image Depth Cues Proprioceptive Cues information from joints and muscles though the nervous system Convergence muscles that rotate the eye in the socket 18

19 Depth Cues Stereopsis using our two eyes that are horizontally separated to obtain supplementary depth cues Retinal Disparity The closer the object, the more obtuse the angle is on the fovea of the eye Depth Cues Binocular disparity is a strong depth cue but it requires creating two images, one for each eye from independent views If the depth cues are not correct, one may become dominant, depth can be exaggerated or the scene may become discomforting to view Using stereo pairs does not fix the problem of Accommodation since we are looking at a flat plane at all times Max separation should be 1/30 th the distance from the viewer to the display 19

20 Artificial Stereoscopic Vision Two images are presented to the user, with some method being used to only allow one image to be seen by each eye Objects will appear behind, at or in front of a screen based on where the angle of our eyes intersects Glasses Based Stereo Anaglyph Passive and inexpensive Only requires rendering the display in two colors Not capable of rendering all colors Monochrome Anaglyph convert to grey scale and assign red channel to the left eye and green and blue to the right 20

21 Glasses Based Stereo Anaglyph Full color Anaglyph assign red channel to the left eye and green and blue to the right Glasses Based Stereo Polarization Restricts light that reaches each eye Two images are projected on the same screen, each with a different polarizing filter Glasses restrict what type of light reaches each eye Two types: Linear Polarized requires the head to stay level Circularly Polarized does not require head to stay level 21

22 Glasses Based Stereo Polarization Produces full-color images and does not feature binocular rivalry Costs 50% more than anaglyph Does not require power or any synchronization with the display Lightweight Requires lower resolution for a single screen or multiple projectors Glasses Based Stereo Shutter Glasses Actively shutters to present light to one eye while blocking light to the other Uses liquid crystal shutter glasses that turn opaque when voltage is applied Use a timing signal to synchronize the display with the glasses using infrared or radio Ghosting or cross talk between glasses can be apparent Require batteries, more expensive 22

23 Glasses Based Stereo Shutter Glasses Ghosting Auto-Stereoscopic Screens Parallax-Barrier Screens Nintendo 3DS Interface a left and right image using a filter to separate what parts are visible Requires exact placement of the eyes to get the proper image 23

24 Auto-Stereoscopic Screens Lenticular Networks Semi-cylindrical lenses in front of interlaced left and right images VR Headsets A separate screen is reserved for each eye with a divider between them, placed very close to the eyes Crystalline lenses alter our accommodation so that we can focus on a point normally too close for our eyes 24

25 Parallax Stereo Pairs Toe-in (where our eyes face inward at a single point) is easy to implement Drawback: projection planes separate vertically If the depth cues are not correct, one may become dominant, depth can be exaggerated or the scene may become discomforting to view 25

26 Stereo Pairs Off-axis Projection planes are lined and is less stressful stereo Requires the use of a nonsymmetric camera frustum Creating the Off-Axis Frustum Calculate widthdiv2 Tan θ = opp adj Tan aperture 2 = widthdiv2 camera. near 26

27 Creating the Off-Axis Frustum Calculate the Frustrum s left, right, bottom, top, near, far Tan θ = opp adj Tan aperture 2 = widthdiv2 camera. near near plane D = 0.5 eyeseparation camera f 0 Tracking & User Environment Tracking the user s pose and actions is important Pose sensors include: 27

28 Tracking & User Environment In a perfect world motion tracking should be: Small Self-Contained Complete (6 degrees of freedom) Accurate ( < 1mm & < 0.1 degrees) Fast ( 1kHz ) Occlusion Free Robust (temp, moisture, radio frequency) Unlimited working area Wireless Cheap Of course, this is impossible to achieve in the real world Mechanical Tracking Assumes direct physical connection between user and measurement device Segments with joints for measuring angles High accuracy and sampling but is complex and introduces motion constraints 28

29 Ultrasonic Tracking Uses high frequency sound to measure distance between a speaker and receiver In dry 20 degrees C sound moves at m/sec Length = c * travel time Three receivers are used in an XYZ configuration Greatest weakness is the changing speed of sound based on temperature, pressure, humidity, and occlusion Optical Tracking / Videometric Optical tracking can use active or passive markers, usually with infrared light Camera lens can be mathematically modeled and using triangulation, a 3D point can be determined Videometric has the camera attached to the user and set points around the room 29

30 Optical Tracking / Videometric Electromagnetic Tracking Based on the local vector of the magnetic field Earth s magnetic field isn t accurate enough Uses a source and a sensor to determine 6 DoF pose Sensors are compact, light and cheap No ferromagnetic materials can be nearby Frequency is limited by the generation of the magnetic fields 30

31 Considerations to Improve Presentation Ghosting leakage of the left eye image to the right eye and the opposite. High Contrast increases ghosting Screen border objects that get cut off by the screen will conflict since it is set as zero-parallax Occlusion by Audience if someone is in front of you it will create conflicting depth cues Motion Cues Animation enhances understanding of depth Vertical Structure - Considerations to Improve Presentation Parallax/Structure Interference frequency of geometry matches parallax separation Noisy Texture high frequency information gives little depth information Mirror Reflections many times we cheat with reflections, with stereo it can create big problems 31

32 Considerations to Improve Presentation Specular Highlights based on camera position and since we have two different cameras, you might get different images Positive Parallax easier to look at, reducing eye-strain Focal Distance Changes quick changes cause eye-strain Causes of Visual Fatigue in Stereoscopic Vision Conflict between accommodation and convergence In artificial vision we accommodate on the screen but converge on the depth of the object During adolescence a link is developed between accommodation and convergence If the disparity is too great it can cause double vision Eyestrain Reduction In Stereoscopy 32

33 VR in Unity HTC Vive Enable Virtual Reality in your Application VR in Unity HTC Vive Remove Oculus and choose OpenVR for HTC Vive Steam and Steam VR are required to make OpenVR applications work on your computer 33

34 VR in Unity HTC Vive For People Using Macs Unity OpenVR requires Metal graphics and 64 bit application and OpenGL is not supported Can work with macos but optimized for High Sierra+ VR in Unity HTC Vive menu sensor trackpad trigger system status light grip micro usb 34

35 VR in Unity HTC Vive Go into your Input Manager Add 16 additional Inputs (18 -> 34) Consult the Unity manual on the controller hardware that is exposed: VR in Unity HTC Vive Example of Input for left and right controller menu buttons Note that to access joystick buttons, we use the syntax: joystick button X 35

36 VR in Unity HTC Vive Example of Input for left trackpad horizontal and vertical axes Note that axis 1 and 2 are labeled the X axis and Y axis in Unity, respectively Note the Dead Zone, this is how far you need to move the trackpad before if starts returning values that are not zero No trackpad / axis is perfect, set your dead zone to some value above zero, or you will get drift! VR in Unity HTC Vive We have three Classes to work with under the XR namespace: XR.XRSettings global XR settings such as: enabled, what devices is loaded, supported devices XR.XRDevice describes the XR device being used, such as: is present, refresh rate, model XR.InputTracking Handling data coming in from the tracking system such as position, rotation 36

37 VR in Unity HTC Vive At any time we could potentially lose connection to our controllers due to Bluetooth issues, battery failure or one thrown through a monitor We need to continually check to see if the controllers are available We can query the connected joysticks using: string[] joysticks = Input.GetJoystickNames(); Vive Controllers have specific names: OpenVR Controller - Left OpenVR Controller - Right Iterating through the array of joystick names and searching for these strings will let us know if they are connected VR in Unity HTC Vive 37

38 VR in Unity HTC Vive We can query button presses as usual with Input.GetKeyDown and use the JoystickButton virtual keycodes: We can query axes based on the names we setup in the Input Manager C# Delegates & Events Think of a delegate as a function pointer They are created using the keyword delegate with the signature of the method afterwards A delegate is able to hold a method and call it later It is the first part in creating Events, which fire off at the correct time and notify subscribers of the event public delegate int DelegateName(int x, float y) Notice that this part looks just like a typical method 38

39 C# Delegates & Events Events work with delegates to fire off when something important happens public event delegatetype InputRecieved; An event will notify everyone who has subscribed Only methods with the delegate s signature are allowed to subscribe to the event! public void HandleLTrackpadHorz() { // Do Something here} C# Delegates & Events We can add and subtract methods to the event using the += and -= operators OnLeftTrackpadHorz += HandleLTrackpadHorz; OnLeftTrackpadHorz -= HandleLTrackpadHorz; When the times comes, our event calls all the methods that has been subscribed Tell all subscribers Player.ReactToInput() Checking if event happened Yes OnInputReceived Movement.Reaction() MenuSystem.DealWith() 39

40 C# Delegates & Events Make your delegates and events Poll for a change, check if anyone has subscribed and fire! Somewhere else make your method and register it VR in Unity HTC Vive XRNode Numeration the possible objects that are being tracked that you can query for information such as position and rotation XRNode.LeftEye left eye XRNode.RightEye right eye XRNode.CenterEye between the left and right eye XRNode.Head user s head XRNode.LeftHand left hand XRNode.RightHand right hand XRNode.GameController not associated with a hand XRNode.TrackingReference stationary physical device XRNode.HardwareTracker device arbitrarily attached to other objects Those in red can have multiples in the scene, require you to call InputTracking.GetNodeStates() 40

41 VR in Unity HTC Vive We can query tracking data such as the position and orientation: VR in Unity SteamVR The SteamVR plugin is also offered on the Unity Asset Store, which provides many helpful scripts and hints at how to use VR successfully Using OpenVR/ OpenXR properly means learning Valve s way of coding For instance, input is handled very differently than we have seen so far in Unity Note, what we are about to go over was released September 21 st, 2018 so it is very new and buggy even I can t get everything to work yet! 41

42 VR in Unity SteamVR Actions Actions in SteamVR are a way to abstract away all the input possibilities Rather than thinking about the controller being depressed by X%, we instead think of the action we want to use, such as Grab There are 6 different types of action Input: 1. Boolean binary, either it is on or off no inbetween 2. Single analog values between 0 and 1 such as a throttle 3. Vector2 X & Y analog such as a touch pad 4. Vector3 not commonly used 5. Pose tracking your VR controllers 6. Skeleton estimates finger orientation One output option - vibration VR in Unity SteamVR Actions Actions are placed in groups called Action Sets Helps to allow the player to rebind your actions Component SteamVR_ActivateSetOnLoad which turns on and off actions based on the scene you are in Activates in Start(), deactivates in OnDestroy() 42

43 VR in Unity SteamVR Input Window Actions are stored in an actions.json file at your project s root Default set is active all the times and the device specific sets are only active while using that device Pressing Save & Generate creates scriptable objects for each action so we can use them in inspectors VR in Unity SteamVR Input Window The first time your game is loaded either your default bindings will be used or SteamVR will ask the user to create a binding or use a community binding Go into Open Binding UI to bind your controls Will take you to a local page to setup the binding 43

44 VR in Unity SteamVR Input Window VR in Unity SteamVR Input Window 44

45 VR in Unity SteamVR Input Window For example, I define my own action called Walk, which is a vector2 type and is mandatory to play the game Create a new script and expose the action and the input source in the inspector VR in Unity SteamVR Input Window 45

46 VR in Unity SteamVR Input Window 46