Manipulating Volume
Rendered Images Using
Intuitive Gestures
Requirements Document
Richard Paris
Richard.a.paris@vanderbilt.edu
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Mission Statement
Once implemented this system will allow the user to have control over various aspects
of volume rendering within a virtual environment using intuitive gestural interfaces. This will
increase the user’s ability to analyze and plan surgeries and give patients the ability to see what
exactly the surgery will entail. This system will also allow for quicker and simpler research to be
performed as a result of the interface that will be created.
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Background Information
In volume rendering there are seven key aspects that must be addressed; the first being
the color transfer function which determines how the any voxel will be colored. The second
aspect is the opacity transfer function which determines the opacity of a given voxel. The next
three are scale, rotation, and translation of the object; these are important to consider because
humans naturally want to pick up move and examine an object. Next is the ability to view 2D
slices of the volume which allows for a greater amount of detail to be shown. Finally
segmentation is the process of splitting up the volume into the discrete objects.
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Users and Stakeholders
Researchers
This group will consist of Dr. Landman, Dr. Bodenheimer and his graduate
students but may be extended to other medical researchers. The motivation of this
group is to gain a better understanding of the data that is being visualized and will use
the system often. These users can be considered expert users given their extensive
knowledge of volume rendering and computing, additionally these users have a
familiarity with virtual environments as it relates to visualization of medical data.
Typically this user will use the system with only soft time constraints; additionally these
constraints will be in the days rather minutes or hours. For this group the system will be
used in a professional setting, these users are paid researchers who are working
together in a collaborative environment to better understand the data. The actual use
will take place mainly within a lab or office environment, this is a result of the current
limitations of virtual environments. Dr. Landman and Dr. Bodenheimer are the
stakeholders of the project while the graduate students are the primary users.
Medical Students
The second group will be medical students who will use the system as a means
of learning about surgical procedures and understanding the organ or system of organs
being viewed. These users can be mainly classified as beginners as they have little to no
experience with volume rendering or virtual environments in general. For users of this
type the task nature can be considered very calm, they will be given guidance and will
use the system for a given amount of time regardless of how much interaction is
completed. The system will be used in a teaching lab with instruction from an expert
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user, this should be considered a work environment and be less collaborative and more
instructional. This group consists of secondary users.
Surgeons
This group will consist of medical professionals, specifically surgeons, who will
use the system as a means to plan surgeries and other medical procedures. This user
group will have varying degrees of frequency of user because it will not be required in all
surgical procedures. This user represents the intermediate user, surgeons typically have
some knowledge of volume rendering and most certainly have a great deal of
knowledge related to the human body, but likely have no experience with virtual
environments or motion capture. The surgeon will be able to use this system to plan
surgeries which results in the task being time critical depending on the severity of the
operation. The surgeon can use this system in a lab or office provided the equipment
can be set up in the room. This can be collaborative, either with fellow and subordinate
surgeons or with the patient or patient’s family. This can also be and individual exercise
as for planning rather than demonstrating the plan as it would be in a collaborative
setting. This group consists of secondary users.
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Inputs
Medical Data
The first input to the system will be the medical data to be visualized, the user
should be able to preselect data to load into the program before entering the virtual
environment. This data will be the primary interaction point for the user, i.e. the user
will work mainly with this data under the scope of this system. At this time the data will
be soft coded (determined at compile time) into the system for ease of development
and testing.
Gestures
The second input will be a set of gestures that will be developed, for this system,
at a later date. These gestures will be distinct from one another and will encompass
nearly all of the interaction with the medical data. This input will be collected using one
of three systems, the 5DT data glove, the Cyber Glove, or the Leap Motion. The former
two device are gloves that the user wears and the tension of the gloves can be
measured to determine the relative positioning of the finger joints. The latter device
tracks up to 10 pointing devices (which includes fingers) within a certain space and gives
those locations to the system.
Hand Position and Orientation
The next input is the position and orientation of each hand and will be used
primarily in determining the context of each gesture but will also be used in conjunction
with certain gestures to make the interaction more fluid. This will be the remainder of
the interaction with the medical data. The position of the hand will use an array of
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motion capture cameras and two wrist bands (one for each wrist) that have motion
tracking spheres attached.
Head Position and Orientation
The final input will be the head position and orientation which will be used to
determine the camera position and orientation, this input will not have an effect on the
interaction with the medical data. This input will be captured using a precise precision
tracking mechanism that utilized four motion capture cameras. This will be mounted on
the head mounted display and calibrated to track the device.
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Outputs
Rendering
The only output of the system is the rendered data and tools to be used within
the system. These tools may be widgets, virtual objects, and/or simply the user’s hands
and will be rendered so that the user can interact with the data. This 3D rendering will
be sent to the head mounted display for viewing by the user.
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Constraints
Computational
The system will be run using 3 computers, the first will take care of hand position
tracking. The next will be responsible for tracking the position and orientation of the
head. The final computer will be responsible for rendering the environment. Therefore
the system requires three computers each capable of performing the outlined tasks as
well as a head mounted display, a motion capture system, and one of the 5DT glove,
Cyber Glove, or Leap Motion.
Physical
The system will be confined to a lab or office environment because it requires a
great deal of computational power as well as three computers to run the system. The
lab will need to be open and have a large area to walk around in, as required by the
motion capture systems. Finally the area will need to be closed off from various outside
effects such as light which can cause errors in the motion capture system. The virtual
environment can only be a certain size, and this size is based on the physical dimensions
of the room.
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Requirements
Functional Requirements
#01 Color Transfer Function Control
The Rationale for this requirement is that the user needs to be able to
control the coloring of the objects for the purposes of visualization and this is
done using the color transfer function.
The Description of this requirement is that the user needs to be able to
create a piecewise linear function from one variable to three within the system
which represents the color transfer function.
The Validation for this requirement is to see if a semi-experienced used
can create a transfer function.
#02 Opacity Transfer Function Control
The Rationale for this requirement is that the user needs to be able to
control the opacity of the objects for the purposes of visualization and this is
done using the opacity transfer function.
The Description of this requirement is that the user needs to be able to
create a piecewise linear within the system that represents the opacity transfer
function.
The Validation for this requirement is to see if a semi-experienced used
can create a transfer function.
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#03 Object Scale Control
The Rationale for this requirement is that the user needs to be able to
expand and contract the volume rendered object to allow for increased detail or
a higher level view of the object.
The Description of this requirement is that the user needs be able to
scale the object interactively while maintaining proper spatial relationships.
The Validation for this requirement is to have a user scale an object to a
set of sizes and ensure that all of these sizes are possible
#04 Rotation Control
The Rationale for this requirement is that it will be easier to rotate the
object rather than walk around it.
The Description of this requirement is that the user needs to be able to
rotate the object along any given axis which will be indicated by a certain
gesture.
The Validation for this requirement is to test and ensure that various
axes of rotation can be created and that the user can rotate the object to a given
set of orientations.
#05 Translation Control
The Rationale for this requirement is that it is easier to move the object
around in the space than to walk to the object.
The Description of this requirement is that the user needs to be able to
move the object to any 3D position within the room.
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The Validation for this requirement is to have the user move the object
along various directions and have the user move the object to a set of locations.
#06 Object Occlusion Control
The Rationale for this requirement is that certain objects do not always
contain the most pertinent information and it would be useful to be able to look
behind the less important objects.
The Description of this requirement is that the user needs to be able to
hide any object in the data. The user then needs to be able to unhide any of
those objects
The Validation for this requirement is to have the user hide every object
in the system in a given order, then unhide them in a different (not reverse)
order.
#07 Cutting Plane Control
The Rationale for this requirement is that viewing slices of data can give a
better more traditional look at the specific object, it can also be easier to
interpret a 2D image in certain circumstances.
The Description of this requirement is that the user should be able to
create a cutting plane along any of the three Cartesian axes.
The Validation for this requirement is for the user to create a cutting
plane in multiple spots along these three axes.
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Non Functional Requirements
#08 Fluidity of Visualization
The Rationale for this requirement is that if the frames per second is too
low the experience diminishes and the user no longer feels as if the system is
interactive.
The Description of this requirement is that the rendering must achieve at
least 10 frames per second.
The Validation for this requirement is to track the frames per second and
ensure that during testing the value stays above 10 for at least 90% of the
interactions.
#09 Robustness
The Rationale for this requirement is that a similar system would be of
benefit for visualizing a number of different data sets such as brain, heart, lungs
etc. rather than just the abdominal data for this project.
The Description of this requirement is that the system must be
transferable to the other data sets.
The Validation for this requirement is to use these other data sets and
ensure the requirements still hold true.
#10 Input Accuracy
The Rationale for this requirement is that precise and accurate gestures
are necessary to control the functions of the system.
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The Description of this requirement is that the system should be able to
routinely identify the gesture being performed as it is being performed.
The Validation for this requirement is to display the gesture being
performed as soon as it is identified and determine if the gesture identified is the
same as intended by the user.
User Requirements
#11 Medical Background Knowledge
The Rationale for this requirement is that users need some medical
background in order to understand the system.
The Description of this requirement is users must have at least some
domain knowledge.
This requirement has no Validation it is up to the user to decide this.
Usability Requirements
#12 Gesture Based Interface
The Rationale for this requirement is that the system is based on using
gestures as input so all actions should be gesture based rather than menu based.
The Description of this requirement is that all actions should be gesture
based rather than menu based.
The Validation for this requirement is that all of the functional
requirements can be achieved without the use of a menu or touch based system.
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#13 Gesture Response Rate
The Rationale for this requirement is that the system should quickly
respond to gestures to ensure that the user is able to control the object as the
interaction is occurring.
The Description of this requirement is the gesture must be determined
within 100 milliseconds.
The Validation for this requirement is to display the gesture being
performed as soon as it is identified and see if a typical user can notice any
undue delay between the action and the response.
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Schedule
Determine what the Leap Motion can do - September 18th
Determine what the users need to be able to do - September 19th
Design gestures for each - September 24th
Implement gestures for cyberglove - September 26th
Implement gestures for 5DT glove - September 28th
Implement gestures for leap motion - September 30th
Develop virtual environment - October 3rd
Design criteria for evaluation - October 5th
Design survey/form to test criteria - October 15th
Perform user evaluation - October 16th - November 5th
Interpret data to decide on the best system - November 12th
Deliver completed project - November 19th