=Paper=
{{Paper
|id=Vol-2299/paper7
|storemode=property
|title=ViReSt - Storytelling with Volumetric Videos
|pdfUrl=https://ceur-ws.org/Vol-2299/paper7.pdf
|volume=Vol-2299
|authors=Gerhard Sprung,Andreas Egger,Alexander Nischelwitzer,Robert Strohmaier,Sandra Schadenbauer
|dblpUrl=https://dblp.org/rec/conf/fmt/SprungENSS18
}}
==ViReSt - Storytelling with Volumetric Videos==
https://ceur-ws.org/Vol-2299/paper7.pdf
ViReSt - Storytelling with Volumetric Videos
Gerhard Sprung, Andreas Egger, Alexander Nischelwitzer, Robert Strohmaier, Sandra Schadenbauer
Dep. Information Management, FH JOANNEUM, Graz, Austria
Email: [first].[last]@fh-joanneum.at
Abstract possible but brings along various technical and content-related
The aim of the project ViReSt is to explore the extent to which problems: in many museums, it not feasible for the exhibit to be
virtual reality, volumetric video and binaural audio can be utilized viewed by only one person at a time [3]. This raises the problem
to create an immersive experience for museum visitors. Museum that everyone sees and hears the same thing. Even if the acoustic
curators should be able to develop, test and create the story information can be perceived independently with the help of
themselves without programming skills. Therefore, a workflow headphones or sound domes [7], the obstacle still arises that the
was developed and tested by creating a small prototype. This playing system must be aware of the identity of the visitor,
prototype was then tested with a group of 10 participants to assess including their previously chosen role [6], the information
immersion, reception of volumetric video and binaural audio.
already received and the path through the exhibition so far. This
Keywords — VR; volumetric video; storytelling
data has then to be used to calculate and coordinate the trajectory
and distinct information that is presented [8].
I. INTRODUCTION However, if the information should also be optically adapted to
the role and trajectory of every particular visitor, this can only
In the near future Virtual Reality (VR) will be mature enough be done by spatial separation like using separate rooms, booths
to be widely used in museums. The project ViReSt (VIrtual or head mounted displays.
REality StoryTelling) addresses the question of how to create
compelling content for such projects. With our prototype, we B. Characters in VR
explored what tools are or would be needed to give museum If a museum uses storytelling to touch visitors emotionally,
designers without programming knowledge the ability to create they have to provide them with believable and convincing
interactive stories that are immersive, emotionally engage protagonists to interact with.
visitors and provide a level of interactivity.
Several researchers found that high behavioral realism and
The “wow-effect”, which is usually sufficient to attract the realistic visualization of the characters in a movie increase the
visitors’ attention to an exhibit that is presented with VR, will believability [9]–[12]. But on the other hand, artists [13] and
no longer suffice as soon as the visitors will already have other researcher stress the problem of the “Uncanny Valley-
experience with VR-devices. In the same way as in the advent Effect” [14]. This effect describes the phenomenon that the
of film and again in the early stages of the computer game audience find small discrepancies in the behavior or the realistic
industry, traditional methods and approaches for creating visualization of extremely realistic characters very disturbing
immersive experiences have to be rethought, reworked, (often described as “eerie”) [14][15][16] whereas a cartoony
redefined or even created from scratch [1]. stylization is very forgiving and can concentrate on the
personality of a character [17][18].
II. STATE OF ART
A. Storytelling in Museums Concerning the creation and digital representation of the
virtual actors there are several technical possibilities.
To offer immersive experiences in museums, several
technologies are currently to be considered. Audio guides with 1) Mesh and Bones
radio plays and spoken stories are already widely used [2][3]
although interactivity is mostly limited to starting and stopping The surface of a digital character is stored digitally and, with
the help of shaders (instructions how to calculate the color of
the recording. There are also approaches where the contents are
location-dependent [5] or the visitors can select a role from each pixel) and light simulations, an image is rendered. Game
engines are capable of creating very realistic scenes in real-time.
whose perspective the story is told [6]. Films are often used,
sometimes presented with methods that increase immersion like To create such so called “meshes” artists can use Computer
the Pepper’s Ghost Effect1, projection mapping, projections on Graphics (CG) programs to construct and sculpt the surface.
spheres and dome projection. Alternatively, real-life persons can be measured and digitized.
Museums try to personalize the visitor’s experience, make it These values can be used to reconstruct the person as a mesh.
interactive and adapt it to interests and needs. The One wide-spread approach to achieve this is by scanning with a
laser, infrared (IR) or structured light. Another approach is the
personalization of the experience during a museum visit is
1 The Pepper’s Ghost effect is an optical illusion that utilizes large pieces
of glass to partly reflect a scene which cannot be directly observed by the
audience. The viewers see the reflections as “ghosts”.
54
ViReSt – Storytelling with Volumetric Videos
calculation of the mesh with the help of Photographs and perspective and their position in the scene as well as influence
Structure from Motion (SfM) or other photogrammetry the story new techniques to plan the experience are needed [27]
techniques. [28].
To animate these meshes usually digital bones are Because of the many different ways a non-linear story can
constructed to provide an underlying structure which is utilized unfold, a system to previsualize an interactive story has to be
to deform the skin. The movement of these bones either can be capable of using variables, conditions and user input. Also it is
animated by an animator (this is known as “keyframe necessary to deal with the distance to the viewer, their possible
animation”) or is acquired from human motion with the help of positions and what the viewer sees [28].
motion capture techniques.
Interactive story editors like Twine4 are designed to create
2) Images and Movies (Billboards) text-based stories. Tools like articy:draft5 (Figure 1) are already
used to create and organize interactive and non-linear game
A second approach is to use 360° movies, often called content. Programs that allow drawing, modeling and animation
spherical or 360/180 movies. In this approach, real-life scenes directly in VR [29][30][31], as well as manipulation of the flow
are filmed with a special camera to record a panoramic view. of an interactive application [32] help to position and control
Therefore, creating an interactive application with this technique visual cues. This prevents situations where the viewers oversee
requires recording all possible versions. If the user makes a important clues for the understanding of the story.
decision, the movie has to switch to the corresponding variation.
It is possible to combine spherical movies with 3D-
representation. Here the spherical movie is projected onto the
background and the characters are placed in 3-D around the
virtual camera. Characters can be represented as 3-D-meshes as
described above or as 2-dimensional objects showing a movie
(this is called a “billboard”). In this case, the shown characters
can be life-action footage or stylized representations.
Such films can then be viewed with Head Mounted Displays
(HMDs) but, apart from the head rotation, they do not allow
much interaction and are accordingly rarely immersive
Figure 1: Articy:draft
experiences.
3) Volumetric Video Although there are tools to support the development of
interactive content, real interactive utilities are still missing in
In order to facilitate Free Viewpoint Video (FVV), order to clearly present and manipulate the complex processes
techniques are developed to store video in a way that the viewer as well as provide visual aids and automatically check for weak
can choose his viewpoint arbitrarily. Volumetric Video allows points and dead ends.
the recording of people and their movement utilizing the depth
information of depth-cameras (“RGBD-camera”) [19][20], 2) Directing
photogrammetry or lasers. To store the results, the surface is In traditional movies the director guides the attention of the
either represented as a point cloud2 [21][22] for each frame of audience by choosing an appropriate frame and therefore
an animation, a dynamic mesh including all movement of the restricts the perceptional boundary. The director can decide
vertices3 or the depth information can be stored separately as an upon the position of the camera (Point of View), the focus,
image. In this way it is possible to store animations without movement of camera and actors and so forth. In 360°-movies
using bones and skin deformations [23][24]. and VR-applications the viewer himself to a high extent is
C. Story Planning for VR choosing the point of view. Although there is important research
being done concerning the use of focus and depth of field in VR,
1) Planning
these possibilities are not yet widely available [33].
In the film industry, the description of a film in form of a In order to increase immersion and to understand the story it
movie script is highly standardized. To prevent ambiguities and is extremely important to make viewers look and move in the
enable effective cooperation scripts are expected to have a right direction at specific times. Therefor the director has to use
special form and structure. Another tool for planning a film, visual [34] and acoustic [27] cues to help the audience to
Storyboards, are visualizations of each shot of the movie. understand what is happening and to guide them through the
Storyboards and the predecessor of the modern movie script story.
(Continuity Scripts) have been used since 1928 [25][26]. With
the help of storyboards, one can virtually watch the movie by If the viewers are able to move freely in the scene, their
looking on the images in the right order. possibilities should be restricted by obstacles (like walls or
fences) in the virtual world. In this case, the visitors have to be
Neither of these methods is applicable for 360° video, VR or provided with methods to cover larger distances. Flying and
interactive storytelling. Since the viewer can choose their being moved in the virtual world often leads to nausea because
2 A point cloud is a set of points in space 5 https://www.nevigo.com/en/articydraft/
3 A vertex is a point in space used to define a mesh
4 http://twinery.org/2
55
ViReSt – Storytelling with Volumetric Videos
of the discrepancies between real movement and the movement
shown in the VR-Application[35][36]. This effect seems to be
independent of the amount of immersion [37]. One promising
approach to tackle this problem is teleporting. By pointing at the
point where one wants to be the viewer instantly changes
position [38][39][40]. Sometimes stories need different ways of
navigating like a wheelchair[41].
One important help to orient in a virtual world is binaural
audio [27]. By manipulating the frequencies of an audio event,
the frequency change occurring in the outer ear (Head Related
Transfer Function HRTF) can be simulated [42][43]. Therefor
the sound seems to be coming not only from the side but also
from above, below or behind [44]. The sound sources are placed
at the appropriate positions in the virtual space. The sound is
manipulated depending on the position of the viewer, the Figure 2: Story structure in Twine
direction of the head and the size and surface of the room and
obstacles, and send to the headphones. Thus the user can B. Recording Volumetric Video
recognize if a sound event is occurring e.g. behind or above him
[45]. The method we have chosen to employ for our proof of
concept is volumetric video. To allow a simple volumetric
With the help of these technologies it is possible to create the representation, we restricted the representation to a 2.5-D
basic conditions for the so-called immersion or presence [46]. representation that spatially visualizes about half of the human
body. Our recording software encodes both the depth and color
III. PROOF-OF-CONCEPT information of a RGBD-Camera as two RGB-images into a
Based on this research we developed a workflow to create movie file. One image containing the color information and one
interactive stories incorporating volumetric video, spatial sound, image the depth information are stored side-by-side (Figure 3).
interaction triggered by various sensors and events and speech
input.
A. Planning
For the first phase –planning- we experimented with
different tools like Twine, several script editing Tools like
celtX6, scrivener7 and Trelby8. Additionally storyboarding tools
like storyboarder9 and articity:draft were evaluated. The highly
branched structure[47][48], which is also dependent on
conditions and variables has led us to exclude all script-editors
and linear storyboarding tools. In future projects we will use
Twine, a simple Editor for interactive text stories which is
capable of visualizing the structure and the flow of the story
(Figure 2). With this software, even variables and conditions can
be defined and interactively tested.
Figure 3: Side by side film
We used the Microsoft Kinect 2, which has 512x424-pixel
resolution for the depth information, which was sufficient for
our tests. To improve the results, we processed the images with
the post-production software Blackmagic Fusion10. We
extracted the background, improved color and contrast, softened
the edges and enhanced the depth information.
C. Editor
To add interactivity, we had to develop an editing application
that was capable of defining objects, events, sensors and triggers
(Figure 4).
6 https://www.celtx.com/index.html 9 https://wonderunit.com/storyboarder/
7 https://www.literatureandlatte.com/scrivener/overview 10 https://www.blackmagicdesign.com/at/products/fusion/
8 https://www.trelby.org/
56
ViReSt – Storytelling with Volumetric Videos
for predefined phrases in the spoken text and reacts accordingly,
e.g. by starting an animation.
To implement binaural audio in our application we used the
Resonance Audio SDK by Google13. Resonance Audio allows
to apply head-related transfer functions (HRTFs) to the
soundfield to enable spatial hearing.
As the space that can be detected by the trackers of the
Oculus Rift HMD is limited, the space of the story had to be
limited accordingly. This was achieved by creating a scene in a
prison cell. The walls of the cell represent the borders of the
space, which could be tracked. It would have been possible to
put real walls where the users saw walls just as it would have
been possible to put real chairs and a bed into the scene. The
downside of this approach is that it would require additional
effort for calibrating the trackers.
Figure 4: Screenshot of the Editor
Objects can play animations and sound files if they are
triggered and all conditions are met. Therefore, features for
defining variables, timers and possibilities for user-input had to
be provided [49]. With this editor, even persons who are not used
to writing code are able to design complex interactive scenes and
branched plots. The resulting definitions of scenes can be tested
in a generic 3D-environment to detect any gaps, loops or dead
ends of the story and to test different paths through the story.
For future applications we will integrate visual editing. For
this purpose, screenshots will be created and displayed in the 3D
environment. The connections between events will be displayed
as lines and the corresponding conditions and variables will be
Figure 5: Screenshot of the application
visualized.
We also intend to introduce interactive story design in a VR- IV. TEST
environment. To assess immersion, reception of volumetric video and of
D. Player binaural audio we conducted user tests on 10 participants at the
ages of 20-26. In a prequestionnaire, the former experiences of
Within the game-engine Unity3D11, a mesh is automatically the participants concerning VR and interactive applications in
prepared utilizing the previously described video containing the museums were surveyed.
depth information (Figure 5). This is achieved by the help of our
vertex-shaders, which refine (“tessellate”) the mesh and displace In the user test, the participants had to explore an interactive
the vertices according to the brightness of the depth-image VR-scene. With a HMD (HTC Vive) and headphones including
stored in the movie. Thus a 3-dimensional object is created and a microphone they were able to experience a scene in a prison
shown in the scene. cell as a prisoner and interact with other persons in the scene.
All actions and reactions of the participants were recorded. With
These volumetric videos are placed in the appropriate a postquestionnaire, they were questioned about their
positions according to a file created by the editor. The runtime- understanding of the situation and their role in the virtual scene,
module (player) displays, starts and ends the presentation of as well as their emotional involvement and satisfaction.
these videos depending on the variables in the scene description.
It also reacts to user inputs to trigger processes and animations. In the second part of the test, we wanted to test the reception
The triggers that are implemented in the application are capable of and reactions to different ways of presenting the volumetric
of responding to gaze (is the viewer actually seeing an object), videos. The participants had to rate different versions of
time events (has something already happened), and the end of visualizations of human characters in the VR-application
other animations. One additional experimental trigger was the (Figure 6).
human voice. The Windows Speech API which is available in
Unity3D provides the required phrase recognition capability12.
We implemented the possibility that under certain conditions the
user can talk to the character in the scene. The engine searches
11 https://unity3d.com/ 13 https://developers.google.com/resonance-audio/
12 https://developer.microsoft.com/en-us/windows/speech
57
ViReSt – Storytelling with Volumetric Videos
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