Technical Issues: Animation

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Technical IssuesAnimation
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Technical IssuesAnimation

• While graphical effects can visualize a game
  world, animation effects are what actually
  breathe life into it.
• Otherwise, you only have a static and motionless
  world.
• Properly animating a game can be costly, but the
  results can be well worth it.
• Hiring of animators and actors.
• Purchase of modeling tools.
• Purchase of motion data or motion capture
  sessions.
• Additional software and hardware resources.

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Technical IssuesAnimation
Screen shot and video of Unreal Tournament 2003.
This game introduced us to some of the best
animation effects at the time.
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Animation Requirementsfor Video Games

• Like graphics, animation is used to support the
  representation element of a video game.
• Animation captures all motions and actions within
  a game and conveys this information to the
  player.
• Animation has the same general requirements as
  graphics, plus a few more resulting from its
  dynamic nature.

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Animation RequirementsBe Smooth

• Sudden or jerky motions in a game can be very
  distracting and very annoying.
• This applies not only to any character or object
  animations, but also to any camera movement in
  the game.
• Remember that the player identifies with the
  viewpoint of the game sudden changes have been
  known to induce motion sickness!
• Instead, animation should be as smooth and fluid
  as possible.

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Animation RequirementsBe Smooth
Screen shot from Mortal Kombat Deadly Alliance.
While graphically impressive, this latest Mortal
Kombat has been criticized for animation thatis
best described as stilted and choppy. Not a
good thing.
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Animation RequirementsBe Smooth
Screen shot from Unreal II The Awakening. The
co-op multiplayer modeis a nice feature to have,
but the animation is so choppy and the frame
rateis so bad that it is very hard to play. Not
up to player expectations at all.
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Animation RequirementsMake Use of Ambient
Effects

• Animation should be used to bring life to
  ambient entities in the game world. This
  includes
• Non player characters.
• Animals, birds, insects, and other critters.
• Plant life.
• Water, clouds, and other terrain effects.
• Other game world entities including doors,
  furnishings, computers, and other objects.
• By animating these entities, the game world will
  seem more vibrant and life-like.

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Animation RequirementsMake Use of Ambient
Effects
Screen shot from the Legend of Zelda The Ocarina
of Time. The world is full of lively animated
entities, including the characters wandering
around, animals, and so on.
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Animation RequirementsStage Action Properly

• It is important to stage action properly for all
  animation in a game.
• This includes
• Choosing a viewpoint that conveys the most
  information about events being animated.
• Isolating events as much as possible so that only
  one thing at a time occupies the players
  attention.
• If this staging is not done properly, the player
  can easily get confused or miss out on vital game
  information.

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Animation RequirementsStage Action Properly
Screen shot from Killer Instinct Gold. TJ
Combos level has interestinganimated effects.
This includes a train that rumbles through every
10-20seconds. If that doesnt distract you, I
dont know what will!
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Animation RequirementsTiming is Everything

• The timing of animation is critically important
  to its success in a game.
• If it is too slow or too fast, it will appear out
  of sync with the rest of the game.
• This can be quite annoying and frustrating,
  especially if it has an impact on gameplay.
• Sometimes, however, playing with timing can lead
  to some interesting special effects and gameplay
  situations.

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Animation RequirementsTiming is Everything
Screen shot from Max Payne. With its
revolutionary bullet time, you canhave John
Woo style animations with slow motion action,
bullets zippingover your head, and so on. Just
like the movies!
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Animation RequirementsTiming is Everything
Screen shot from Jet Li Rise to Honor. A cool
fighting game with lots of features, including
bullet time (that lets you change directions
mid-flight). Some have called this the most
flagrant abuse of bullet time ever seen.
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Animation RequirementsAnticipate and
Follow-through

• Anticipation is an indication of action to come.
• Follow-through is the reaction that happens after
  the action.
• In most cases, realistic actions have both an
  anticipation and a follow-through.
• For example, a character should bend its knees
  both before jumping and when landing.
• The absence of anticipation and follow-through
  removes some of the realism and consistency of
  your game.

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Animation RequirementsAnticipate and
Follow-through
Screen shot and animation from NBA Live. Jumping
is done properly, as one can see a player prepare
to jump and also see them stickthe landing
properly. Anticipation and follow-through are
donenicely in this case.
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Animation RequirementsSecondary Motion

• When animating a character, you should first
  focus on animating its primary motion, such as
  arms and legs moving.
• Be sure, however, not to ignore a characters
  secondary motions.
• This includes things such as hair and clothing
  movement, and so on.
• While this can take lots of time to do, it can be
  well worth it in the end.

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Animation RequirementsSecondary Motion
Screen shot from Dead or Alive 3. A lot of
attention is paid to animating secondary motion
of hair, clothing, and so on.
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Animation RequirementsBe Representative

• The animations of a character or an object should
  reveal or reflect their various properties and
  behaviours.
• For example, a rubber ball would distort when
  bounced on the floor, whereas a metal ball would
  perhaps only wobble or resonate.
• This helps reinforce consistency and immersion in
  a game, as characters and objects would act in a
  way that is fitting and suitable to themselves.

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Animation RequirementsBe Representative
Screen shot and video from Dead or Alive 3. The
animation of each character, including Brad Wong
above, reflects their personality, behaviour, and
fighting style in the game.
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Animation RequirementsObey Appropriate Laws

• It is important for animation to follow
  appropriate laws of physics and nature according
  to the type of game being played.
• This includes gravity, friction, momentum,
  skeletal mechanics, acceleration, force transfer,
  and so on.
• It does not matter whether these laws are
  realistic or not, as long as they are in sync
  with the players expectations of the game.
• Depending on the genre and style of game, physics
  and natural laws can be realistic or more
  cartoonish.
• Supporting player expectations is the key!

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Animation RequirementsObey Appropriate Laws
Screen shot from Oni. Despite being unconscious,
the guard has absolutelyno difficulty in keep
his legs in the air. Such disrespect for the law
ofgravity is quite noticeable to the player.
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Animation RequirementsObey Appropriate Laws
Video from Unreal Tournament 2003. Note the
realistic skeletal mechanics when you fall and
die. Bodies will shape themselves toterrain
quite naturally.
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Animation RequirementsObey Appropriate Laws
Videos produced using the Havok 2 game engine.
These showsome really nice animation effects
based on physics and accurate modelsof the game
characters. This engine is used in Max Payne 2,
Half Life 2,and Deus Ex, Invisible War.
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Animation RequirementsBe As Dynamic As Possible

• Instead of using a small number of preset
  animations, better results can sometimes be
  achieved by dynamic animation techniques.
• Fluidly chaining a number of short animations
  together to form a large variety of longer
  animation sequences.
• Providing the user the ability to define their
  own animations based on the structure of the game
  characters and objects they interact with.
• Letting your physics engine drive your
  animations.
• Doing this effectively can add depth and a lot of
  variety to animations in games.

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Animation RequirementsBe As Dynamic As Possible
Screen shot of Die by the Sword. This was an
innovative title that gave theplayer total
control over how the hero wielded his weapon
direction,force, momentum, and so on. By proper
mouse movements, or key presses,you could slice
apart your opponents in a stunning variety of
ways.
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Animation RequirementsBe As Dynamic As Possible
Screen shots from Stair Dismount (above left),
Truck Dismount (above right),and Dismount Levels
(bottom right). These are incredibly fun little
games that employ some interesting dynamic
animation and rag doll physics. Expect to waste
lots of time with these gems!
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Animation RequirementsBe As Dynamic As Possible
Screen shot and video of Rag Doll Kung Fu. In
this game, there are no pre-scripted animations.
Instead, players have total control over moving
charactersby grabbing a part of the body and
moving around the screen. An interestingconcept
in which players can define their own fighting
moves!
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Animation RequirementsBe As Dynamic As Possible
Screen shots and movies from Pseudo Interactives
Crash demos. These demos show off new lighting
and shading techniques, new physics models,and
some pretty cool dynamic animation techniques.
The demos are basedon Microsofts new cross
platform XNA technologies. Hopefully all
carcrashes in games will look like this soon!
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Animation Techniques

• There are a variety of different techniques for
  providing animation in video games.
• Among these are the following
• Simple animation effects.
• Rigid body animation.
• Articulated structure animation.
• Dynamic simulation.
• Particle animation.
• Behavioural animation.

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Simple Animation Effects

• There are several simple animation tricks that
  can be done in real-time.
• These are some of the first techniques, and are
  therefore hardware based.
• Palette or colour map animation
• Simple animation effects are achieved by
  manipulating the palette or colour map of a
  bitmap or texture (also known as look-up-table
  animation).
• Hardware based sprite animation
• Some graphics hardware has support for sprites,
  and allows motion and other manipulations. (In
  some cases, this is how mouse cursors are
  implemented.)

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Simple Animation Effects
A simple example of palette animation. This is
simple colour cycling, where colours of the
palette are merely shifted to produce an
animation. Similar techniques can be used to
produce waterfalls, waves, and so on.
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Simple Animation Effects
A more impressive demonstration of palette
animation. It can be usedto create a variety of
effects with minimal difficulty.
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Rigid Body Animation

• Rigid body animation is a relatively simple form
  of animation that is an extension of existing
  rendering techniques.
• Animated scenes can be produced simply by
  rendering a scene with objects in different
  positions and orientations.
• The problem is, however, how do we specify and
  control the movement of objects in a scene?
• There are two main approaches to doing this
• Keyframing or interpolation.
• Explicit scripting.

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Rigid Body AnimationKeyframing or Interpolation

• Keyframing systems are based on a well-known
  production technique in traditional animation.
• To cope with lengthy animations, companies
  adopted a hierarchical system in which lead
  animators specify a sequence by drawing keyframes
  at certain intervals.
• Other animators would then draw the intermediate
  frames to complete the animation.
• This same approach can be taken for animation in
  video games.
• The participants, however, are different.

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Rigid Body AnimationKeyframing or Interpolation

• In this case, animators specify the keyframes
  themselves, and a computer will generate the
  intermediate frames.
• Usually, this generation uses some form of
  mathematical interpolation.
• Linear interpolation is simple, but this approach
  on its own is often inadequate.
• Non linear interpolation (for example, with
  splines) can sometimes provide better, or more
  realistic results.
• Sometimes, however, interpolation still does not
  produce what the animator is looking for.

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Rigid Body AnimationKeyframing or Interpolation
Original keyframes fora bouncing ballanimation
sequence.
Animation pathgenerated usinglinear
interpolation(not very realistic).
Animation pathgenerated usingnon linear
interpolation. The bounce is morerealistic
this time.
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Rigid Body AnimationExplicit Scripting

• Explicit scripting is a process that allows
  animators to specify the complete animation path
  of objects.
• This includes
• Changes in object position, orientation, and
  other characteristics.
• Changes in object velocity and acceleration.
• Scripting can be done in a graphical or
  mathematical fashion.

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Rigid Body AnimationExplicit Scripting
Finish
V
Start
Finish
Start
Animation path of an object (left) along with its
velocity curve (right). Combining the two
together, the position of the object in its
animationcan be determined quite easily using
this simple scripting.
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Articulated Structure Animation

• The premise behind articulated structure
  animation is that many objects have an underlying
  structure that dictates the kinds of motions the
  object is capable of.
• This includes a variety of game elements
• Game characters.
• Animal and plant life.
• Non rigid composite objects.
• Because of this underlying structure, special
  considerations are necessary.

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Articulated Structure Animation

• To support this kind of animation, the underlying
  structure of an object must be defined in
  addition to any surface modeling.
• This structure is a collection of rigid objects
  connected by joints which enable the parts of the
  structure to move with respect to one another.
• For example, the skeleton of a game character
  must be provided in addition to a polygonal mesh
  for realistic animation.

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Articulated Structure Animation
Sample skeleton model for a game character. By
defining a skeleton,and attaching surface
polygons, we have a fully articulated
modelsuitable for animation purposes.
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Articulated Structure Animation

• Animation with these articulated structures is
  accomplished using similar approaches to rigid
  body systems
• Keyframing or interpolation.
• Explicit scripting.
• This time, animation is defined in terms of joint
  movement in the structures.
• Corresponding polygons attached to the structure
  move accordingly.
• When rendered in the game with textures, the
  animation is complete.

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Articulated Structure Animation
Sample animations of a game character running
(left) and jumping (right). By manipulating the
underlying articulated structure, it is
possibleto generate some reasonably realistic
animation.
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Articulated Structure Animation
Sample completed animation with polygonal model,
shading, and texturing complete.
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Articulated Structure Animation
Another completed example, where you can view the
skeleton, joints, wireframe, and the final
textured and shaded result.
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Dynamic Simulation

• The previous animation techniques involve
  specifying the motion of game entities with
  little regard for the laws of the game world.
• Dynamic simulation involves the rigorous
  application of physical and natural laws to
  simulate motion for animation.
• The basic premise is that adherence to these laws
  should produce more realistic or natural
  animation than more traditional techniques.
• The problem is, however, that doing this removes
  artistic control from the animator.

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Dynamic Simulation

• The general approach to dynamic simulation
  animation is
• Determine which laws you wish to apply to the
  game world and all of its objects.
• Define the game world and its objects, ensuring
  you have all of the required attributes and
  information.
• Identify the motions you want the objects to
  exhibit.
• Simulate the motions and save the results.
• If this does not produce the desired animation,
  game world and object data may need tuning, or
  artistic intervention is necessary.

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Dynamic Simulation
Sample pictures and animations of aliens using
dynamic simulation, as well as more traditional
techniques.
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Dynamic Simulation
Examples of dynamic animation using the open
source physics engine called the Open Dynamics
Engine (ODE). It has been used in avariety of
games, simulation tools, and other 3D
applications.
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Dynamic Simulation
Screen shots and demos from the Tokamak physics
engine. While notopen source, the Tokamak
engine is freely available. It has been usedin
several games, and features include object
breakage, ragdoll physics,stacking, particle
effects, collision detection, and so on.
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Dynamic Simulation
Screen shots and demos of the Newton Game Dynamic
engine. Onceagain, this is a free engine that
can be used in conjunction with a varietyof
tools, programming languages, and other game
engines.
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Dynamic Simulation
Examples of dynamic animation using the Meqon
physics engine.3D Realms has announced it is
using Meqon in Duke Nukem Forever.Ill believe
it when I see it.
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Particle Animation

• Particle animation refers to the animation of a
  large population of independent particles to
  simulate some phenomenon.
• This phenomenon is viewed as the overall movement
  of the collection of particles.
• This form of animation can be used to model
  several different kinds of effects
• Smoke, clouds, fire, explosions, sparks, debris,
  tornados, sand storms, and so on.

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Particle Animation

• Each particle behaves relatively independently,
  according to some kind of scripted behaviour.
• Each frame of a particle animation is generally
  constructed as follows
• New particles are generated and injected into
  the current system.
• Each new particle is assigned its individual
  attributes.
• Any particles that have exceeded their lifetime
  are extinguished.
• The current particles are moved according to
  their scripted behaviour.
• The current particles are then rendered.

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Particle Animation
Particle animation can add greatly to the special
effects in a game, as shown in this image and
demo.
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Behavioural Animation

• Behavioural animation means modeling the
  behaviour of game world objects.
• This is more complex than just basic movement.
• This depends on certain behavioural rules and
  attributes defined for each object.
• This may also depend upon the behaviour of
  nearby objects as well.
• A collection of entities in behavioural
  animation evolve according to the behaviour of
  neighbours in the population.
• The goal is to make the collection look realistic.

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Behavioural Animation
Screen shot and video from Dead or Alive 3. The
animation of each character, including Brad Wong
above, reflects their personality, behaviour, and
fighting style in the game.
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Behavioural Animation
Screen shots from several flocking programs with
different behaviours. (Go back to our artificial
life/flockingdiscussion for more information.)
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Motion Capture Acquiring Data for Animation

• Where does data come from to create realistic
  animations in games?
• Typically, such data is the result of some kind
  of motion capture process.
• This technique is growing in popularity, and is
  now in use in many video games.
• It has been around since at least 1915, when
  rotoscoping was invented to assist in cartoon
  production.

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Motion Capture Acquiring Data for Animation
Clip from the Simpsons. No one does motion
capture better than Homer!
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Motion Capture Techniques

• Motion capture data can be collected in a variety
  of different ways.
• Rotoscoping
• Traditional video of motion is projected onto
  paper or a computer screen, one frame at a time,
  where it is traced for use in character
  animations.
• Optical motion capture
• Reflective markers at key points on the subject
  are captured by several cameras this data is fed
  into and analyzed by computers to produce the
  motion capture data.

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Motion CaptureTechniques
Screen shot of Karateka. Created in 1986, this
is perhaps the first video game to use motion
capture, with all character animationscreated
with the help of rotoscoping.
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Motion Capture Techniques
Images from a motion capture session of Roger
Clemens for 989 Sports MLB 2002. On the left
is Clemens suited for optical motion capture on
the right are the generated skeletal models and
final textured representation.
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Motion Capture Techniques

• Electromagnetic trackers
• The subject is fitted with several sensors that
  measure their spatial relationship to a nearby
  transmitter generating an electromagnetic field
  their data is then fed into a computer.
• Electromechanical suits
• The suit is composed of a group of structures
  linked by some form of angular measurement
  devices located at the major joints of the
  subject. The suit is driven by the subjects
  actions, with all data from the measurement
  devices recorded by a computer.

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Motion Capture Techniques
Pictures of an electromagnetic tracking system
(left) and anelectromechanical suit (right) for
motion capture.
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Motion Capture Techniques

• Digital armatures
• These are posable models constructed out of rigid
  modules connected by joints whose rotations are
  measured by angular sensors.
• There are two kinds of armatures stop-motion
  armatures (used in keyframing) and puppeteering
  armatures (used in real-time).
• The motion capture techniques listed on these
  last few slides vary in expense, resolution and
  sampling capabilities, and general availability.
• It is important to weigh the various factors in
  choosing which motion capture is right for you.

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Motion Capture Techniques
Picture of the Monkey 2 modular digital armature.
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Motion Capture Issues

• The following are issues to consider when
  considering motion capture for a game
• Do you want realistic motion?
• Can the desired data be successfully captured?
• Do you have the budget and time to afford motion
  capture for the project?
• Do you have the budget to hire the talent
  (actors, athletes, and so on) for the session?
• How do you choose and locate the talent to use?
• Which actions do you want captured and which will
  you use traditional techniques on?
• Do you have the software tools and skills on your
  development team to effectively use the data once
  it has been captured?