IAT 241

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IAT 241

• Jay C. Page

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What is Animation?

• Series of still images
• Perception of continuous motion
• Persistence of vision
• Suspension of disbelief
• Rules of reality need not apply

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History of Animation

• Ancient wall carvings
• Roman paintings with pillars
• Zoetrope
• Flip Book and other mechanisms
• Film
• Drawn (flat artwork)
• Stop Motion (real objects)
• Computer Generated (no objects)

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Frame Rate

• Time as uniform discrete chunks
• Frames per Second (FPS)
• Important Frame rates 8 , 24, 30, 60
• Stroboscopic effects
• Strobe appearing to stop rotation
• Wheels seem to spin backwards

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What is 3D ?

• What is 2D ?
• What is 1D ?
• What is D ?

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Cartesian Coordinates Review

• 1D is a number line
• Counting can be absolute or relative
• 2D is 2 perpendicular axes (x, y)
• 3D is 3 perpendicular axes (x, y, z)

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3D Planes

• 3 unique planes exits between axes
• XY Plane between X and Y axes
• XZ Plane between X and Z axes
• YZ Plane between Y and Z axes

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3D Polygonal Object

• Vertices (plural form of vertex)
• Edge(s)
• Face(s)
• Normal(s)

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Anatomy of a 3D object

• Vertex list
• Face List
• Extra data for vertices or faces
• Transformation Matrix

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Transformations

• Translation (movement)
• Rotation (spinning)
• Scale (size)

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Translation

• All parts of an object move together specified by
  X, Y, Z values

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Rotation

• All parts of an object spin together around a
  common center.
• Rot. center is described as an axis.
• ie Rotating around X, Y or Z axis by a certain
  number of degrees.
• These are known as Euler angles.

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Scale

• All parts of an object move towards or away from
  a common center.
• Scale is a multiple. ie 0.5 is ½ size
• Scale is applied independently along each axis

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Coordinate systemsGlobal

• Global coordinate system axes are absolute and
  universally oriented the same.
• The global axes can be configured in different
  ways. ie Z up or Y up

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Coordinate SystemsLocal

• Local coordinate systems are relative to their
  reference system.
• Their 3 perpendicular axes may be oriented in any
  direction.

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Projecting 3D onto 2D

• Perspective and Orthographic projections are
  used.
• Cameras are used to define perspective
  projections and associated parameters.

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Orthographic Projections

• In Orthographic projections, parallel lines
  remain parallel.
• No matter how far away an object is it will
  remain the same size.
• Multiple orthographic projections are needed to
  properly locate objects.

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Perspective Projections

• Parallel lines converge in the distance.
• The farther away an object is, the smaller is
  appears.
• Field of View (FOV) is the angle which describes
  the edges of the projection plane and perspective
  amount.

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Clipping Distance

• Objects farther from the camera than the clipping
  distance will not be projected.

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End of Slides