GPH 338 Computer Animation Survey

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GPH 338Computer Animation Survey
GPH 338 Computer Animation Survey

• Poly/NURBS/Subdiv
• --Winny

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What are the basic pieces?
GPH 338 Computer Animation Survey

• Curves one dimensional objects
• Linear curve line segments
• NURBS curved pieces (splines) using control
  vertices
• Bezier curve splines using tangent handles
• Surfaces two dimensional objects
• Polygonal surfaces (Mesh) Polygons
• Subdivision surfaces Subdivided Polygons
• NURBS surfaces flexible rectangles, bounded by
  NURBS curves
• Solids three dimensional pieces

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GPH 338 Computer Animation Survey
Polygons Polygonal surfaces (Mesh)
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GPH 338 Computer Animation Survey
Polygons are made up of several components
Vertices Edges Faces UVs
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Polygon Primitives
GPH 338 Computer Animation Survey

• Standard
• Parametric can vary their attributes
• vertices, edges, faces, subdivlevel
• Use them when appropriate

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Polygons
GPH 338 Computer Animation Survey

• Simple pieces,
• may need many
• Can build surfaces with strange shapes easily
• Rendered directly
• Efficient
• Good for games
• Need many polygons for a smooth surface (large
  files!)

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Mesh Editing
GPH 338 Computer Animation Survey

• Moving the mesh around, without changing its
  underlying topology (structure)
• Manipulate vertices, edges, faces
• Translate (Move)
• Rotate
• Scale

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Mesh Editing
GPH 338 Computer Animation Survey

• 2. Changes to mesh topology
• (the underlying pieces and the way they are
  connected)
• Subdividing
• Extruding
• Merging Edges
• Deleting
• Messes up UV coordinates (texturing)

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Poly Boolean operations
GPH 338 Computer Animation Survey

• Intersection
• Union
• Difference
• Good for solids
• Many animators
• avoid them
• Messy mesh
• Loss of control

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Polygon examples
GPH 338 Computer Animation Survey
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GPH 338 Computer Animation Survey
Polygon Texture unwrap Sample
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GPH 338 Computer Animation Survey
NURBS surfaces Non-Uniform Rational
B-Spline Flexible rectangles, bounded by NURBS
curves
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NURBS
GPH 338 Computer Animation Survey

• Flexible Rectangles Smooth
• Made by Isoparms
• U
• V
• Manipulated by Few points (CV)

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GPH 338 Computer Animation Survey
Flexible rectangles
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GPH 338 Computer Animation Survey
NURBS surfaces bounded by NURBS curves
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NURBS Curves
GPH 338 Computer Animation Survey

• Made up of many spans -piece of curve between two
  edit points
• Control Vertices (CVs)
• Doesnt pass through them!
• Heads towards them
• Hull - A loop of Control

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NURBS curves
GPH 338 Computer Animation Survey

• Maya Curve Tools
• CV tool
• Control vertices
• EP
• Edit points
• Pencil tool
• Probably want to rebuild
• Degree
• 1 Linear Curve
• 3 default for splines
• Higher can turn tighter, requires more points

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NURBS Primitives
GPH 338 Computer Animation Survey

• Standard
• Parametric can vary their attributes
• of isoparms, Hull, control vertices, etc.
• Use them when appropriate

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Surfaces from Curves
GPH 338 Computer Animation Survey
Extrude / Sweep
Loft
Surface from boundary
Revolve / Lathe
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Attaching NURBS Surfaces
GPH 338 Computer Animation Survey
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Trimmed NURBS Surface
GPH 338 Computer Animation Survey
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NURBS
GPH 338 Computer Animation Survey

• A particular model may be made up of many NURBS
  surfaces
• Not necessary one patch, can be several patch
  stitched together

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NURBS
GPH 338 Computer Animation Survey

• Great for organic, flowing surfaces
• Made by a lot of patches, usually not one
  surface.
• Not many control points needed
• Hard to get fine control (e.g., this vertex
  here!)
• UV coordinates are convenient for many reasons
• Can draw on them!
• Can put objects on them
• Easy to texture??
• Expensive for animation
• Expensive for Rendering, Usually converted to
  polygons for rendering (!)

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Subdivision Surfaces- Subdivided Polygons
GPH 338 Computer Animation Survey
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Subdivision Surfaces
GPH 338 Computer Animation Survey

• Subdivide polygons
• Hierarchy of polygons
• Manipulate at different levels

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GPH 338 Computer Animation Survey
Poly to Subdiv examples
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GPH 338 Computer Animation Survey
SubDiv Surface
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Subdivision Surfaces
GPH 338 Computer Animation Survey

• Good for complicated topology
• (This is difficult to make out of rectangles)

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GPH 338 Computer Animation Survey

• NURBS/Polygons/SubDs? It depends
• Polygons
• More efficient for animation and rendering
• Good for arbitrary topology and Texture UV
• NURBS
• Good for surfaces easily described in terms of
  flexible rectangles
• Simple manipulation, more natural for many curved
  surfaces
• Rendering is complicated
• SubDs
• Extremely handy for modeling, go back and forth
  from poly to SubD
• Heavy
• The best way is combine all together and use all
  their advantage!

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GPH 338 Computer Animation Survey
It will be really useful to use drawings as
reference.
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No matter whatKeep your model Simple Clean!
GPH 338 Computer Animation Survey

• Save a lot of work for Texturing
• Save a lot time for rendering
• Easy for later modify
• Good start for animation