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GPH 338 Computer Animation Survey. GPH 338 Computer Animation Survey. Poly/NURBS/Subdiv --Winny. GPH 338 Computer Animation Survey. What are the basic pieces?. Curves – one dimensional objects Linear curve: line segments NURBS: curved pieces (splines) using control vertices

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Gph 338 computer animation survey

GPH 338 Computer Animation Survey

GPH 338Computer Animation Survey

Poly/NURBS/Subdiv

--Winny


What are the basic pieces

GPH 338 Computer Animation Survey

What are the basic pieces?

  • 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


GPH 338 Computer Animation Survey

Polygons

Polygonal surfaces (Mesh)


GPH 338 Computer Animation Survey

Polygons are made up of several components:

Vertices

Edges

Faces

UVs


Polygon primitives

GPH 338 Computer Animation Survey

Polygon Primitives

  • Standard

  • Parametric – can vary their attributes

    vertices, edges, faces, subdivlevel…

  • Use them when appropriate


Polygons

GPH 338 Computer Animation Survey

Polygons

  • 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!)


Mesh editing

GPH 338 Computer Animation Survey

Mesh Editing

  • Moving the mesh around, without changing its underlying topology (structure)

  • Manipulate vertices, edges, faces

  • Translate (Move)

  • Rotate

  • Scale


Mesh editing1

GPH 338 Computer Animation Survey

Mesh Editing

2. Changes to mesh topology

(the underlying pieces and the way they are connected)

  • Subdividing

  • Extruding

  • Merging Edges

  • Deleting

  • Messes up UV coordinates (texturing)


Poly boolean operations

GPH 338 Computer Animation Survey

Poly Boolean operations

  • Intersection

  • Union

  • Difference

  • Good for solids

  • Many animators

    avoid them

    • Messy mesh

    • Loss of control



GPH 338 Computer Animation Survey

Polygon Texture unwrap Sample


GPH 338 Computer Animation Survey

NURBS surfaces

Non-Uniform Rational B-Spline

Flexible rectangles,

bounded by NURBS curves


Nurbs

“Flexible Rectangles” Smooth

Made by Isoparms

U

V

Manipulated by Few points (CV)

GPH 338 Computer Animation Survey

NURBS



GPH 338 Computer Animation Survey

NURBS surfaces

bounded by NURBS curves


Nurbs curves

GPH 338 Computer Animation Survey

NURBS Curves

  • Made up of many spans -piece of curve between two edit points

  • Control Vertices (CV’s)

    • Doesn’t pass through them!

    • Heads towards them

  • Hull - A loop of Control


Nurbs curves1

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

GPH 338 Computer Animation Survey

NURBS curves


Nurbs primitives

GPH 338 Computer Animation Survey

NURBS Primitives

  • Standard

  • Parametric – can vary their attributes

    • # of isoparms, Hull, control vertices, etc.

  • Use them when appropriate


Surfaces from curves

GPH 338 Computer Animation Survey

Surfaces from Curves

Extrude / Sweep

Loft

Surface from boundary

Revolve / Lathe


Attaching nurbs surfaces

GPH 338 Computer Animation Survey

Attaching NURBS Surfaces


Trimmed nurbs surface

GPH 338 Computer Animation Survey

Trimmed NURBS Surface


Nurbs1

GPH 338 Computer Animation Survey

NURBS

  • A particular model may be made up of many NURBS surfaces

  • Not necessary one patch, can be several patch stitched together


Nurbs2

GPH 338 Computer Animation Survey

NURBS

  • 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 ($!)


Subdivision surfaces subdivided polygons

GPH 338 Computer Animation Survey

Subdivision Surfaces- Subdivided Polygons


Subdivision surfaces

GPH 338 Computer Animation Survey

Subdivision Surfaces

  • Subdivide polygons

    • Hierarchy of polygons

    • Manipulate at different levels


GPH 338 Computer Animation Survey

Poly to Subdiv examples



Subdivision surfaces1

GPH 338 Computer Animation Survey

Subdivision Surfaces

  • Good for complicated topology

  • (This is difficult to make out of rectangles)


GPH 338 Computer Animation Survey

NURBS/Polygons/SubD’s? 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

  • SubD’s

    • 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!


GPH 338 Computer Animation Survey

It will be really useful to use drawings as reference.


No matter what keep your model simple clean

GPH 338 Computer Animation Survey

No matter what…Keep your model Simple & Clean!

  • Save a lot of work for Texturing

  • Save a lot time for rendering

  • Easy for later modify

  • Good start for animation …


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