VR UI, Notes on Projects, Intro' to Object Descriptions

1
VR UI, Notes on Projects,Intro. to Object
Descriptions

• Glenn G. ChappellCHAPPELLG_at_member.ams.org
• U. of Alaska Fairbanks
• CS 481/681 Lecture Notes
• Wednesday, February 25, 2004

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ReviewVR TRANSF 1/2

• In terms of transformations, one of the trickier
  parts of VR is moving objects together in an
  arbitrary frame of reference.
• For example, moving an object with the wand.
• To draw an object in the wands frame of
  reference
• glPushMatrix()
• glTransform(myUser.getTransf(USR_WAND))
• // Draw transformed objects
• glPopMatrix()

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ReviewVR TRANSF 2/2

• To find where the wand points
• vec wandDir myUser.getFrontVec(USR_WAND)
• How do we turn this into a 2-D vector (no
  up/down)?
• Solution 1
• wandDir1 0.
• wandDir wandDir.normalized()
• Solution 2
• wandDir - wandDir.component(vec(0.,1.,0.))
• wandDir wandDir.normalized()

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VR User InterfaceThree Hard Problems

• In CS 381, we discussed view the world and
  move in the world interfaces. We also discussed
  picking, keyboard-handling, and menus.
• There are three problems here
• How to Navigate
• Move in the World
• Flying, driving, etc.
• How to Manipulate Objects.
• View the World
• Picking
• How to Initiate Actions
• In other words, how to tell the computer what you
  want
• Picking, keyboard, menu
• All of these are trickier in VR.

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VR User InterfaceNavigation 1/2

• In VR we are generally either moving around on a
  floor/ground surface, or in the air/space.
• In the latter case, we can have a uniform up
  direction or not.
• Or we may not be able to move at all.
• This gives four general types of navigation
• None
• Like most desktop programs objects move, but the
  user is stationary.
• Sort of
• Walking/Driving
• We still might allow stairs, bridges, elevators
• Airplane-style Flying
• Up is always up.
• Spaceship-style Flying
• Anything goes.

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VR User InterfaceNavigation 2/2

• Four Types of Navigation
• None
• Walking/Driving
• Airplane-style Flying
• Spaceship-style Flying
• What would be a useful UI for each of these?

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VR User InterfaceObject Manipulation 1/2

• When we manipulate objects, we deal with the
  following
• Can we pick up an object?
• If so, how do we determine which one?
• How do we drop it?
• What does it do while it is grabbed?
• Can we move an object without picking it up?
• How?
• Can we perform actions with/on an object without
  moving it?
• What things?
• Similar questions to those above

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VR User InterfaceObject Manipulation 2/2

• Other Problems
• How to deal with clutter?
• How to limit the number of actions we can perform
  so that users dont have to learn remember a
  lot, and internal object interfaces are simpler?
• How can we write object interfaces so that all
  objects can coexist in a friendly way?

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VR User InterfaceInitiating Actions

• More generally, we have the problem of how to
  tell the computer what to do.
• Remember, we are in a VR environment. Users
  already know how to deal with reality (we hope).
  How can we make use of this knowledge?
• Users have 3-D input devices. So, for example,
  treating the wand like a 2-D mouse is silly.
• There is no keyboard.
• Menus are a pain, as usual.

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Notes on ProjectsOverview

• 100 points of your grade in this class will be a
  project.
• Projects will be graded via a contract system
• Each student individually negotiates project
  requirements with me.
• If all requirements are met, then you get 100.
• Proposed requirements are due, as part of
  Assignment 5, in a couple of weeks.
• Your grade on Assignment 5 has nothing to do with
  your grade on the project.
• General requirements
• Projects will be due on Thursday, April 22.
• It is generally expected that you will turn in a
  preliminary version two weeks before that
  (Thursday, April 8).
• In your project proposal, specify what the
  preliminary version will include.
• If, for some reason, you think you need to handle
  the preliminary version differently, put this in
  your proposal.
• Some documentation is required. It need not be
  extensive.
• Plan to do a short in-class presentation as well.

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Notes on ProjectsWhat to Do?

• For project length and difficulty, think in terms
  of four regular assignments.
• Possible topics
• Implement, and use in a program, some
  (relatively) advanced CG method.
• Ray tracing?
• Try out some new user-interface idea.
• A navigation method in VR, etc.
• Two words VR game (okay, thats three words).
• 3-D fractals, chaos, or whatever.
• Something else
• Use of VR Juggler the Discovery Lab is
  encouraged, but not required.

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Intro. to Object DescriptionsOverview 1/2

• Descriptions of surfaces (and thus of 3-D
  objects) can be roughly split into three types
• Polygon List
• A list of the polygons (and/or polylines, points)
  that make up a surface.
• Example triangle (0, 0, 0), (0.5, 0, 0), (1,
  1.2, 0) triangle (1, 1.2, 0), (0.5, 0, 0), (2,
  1, 1).
• Explicit Description
• Surface is described explicitly, using formulae.
• We call this a parametric surface.
• Example (s, t, t2), for 0 ? s ? 1 and 0 ? t ? 1.
• Implicit Description
• Surface is described implicitly, using equations.
• Example x3 3xyz3 4z2sin y 8.

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Intro. to Object DescriptionsOverview 2/2

• Again
• Polygon List
• Explicit Description
• Implicit Description
• So far, we have dealt only with polygon lists.
• Now, we look at
• Pros Cons of the above three.
• Using formulae to describe curves and curved
  surfaces.
• Splines Generating useful explicit descriptions
  based on control points.
• Implicit surfaces and their applications.