gph 338 computer animation survey
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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 - PowerPoint PPT PresentationTRANSCRIPT
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GPH 338 Computer Animation Survey
GPH 338Computer Animation Survey
Poly/NURBS/Subdiv
--Winny
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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
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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 EdgesFaces UVs
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Polygon Primitives
• Standard• Parametric – can vary their attributes
vertices, edges, faces, subdivlevel…• Use them when appropriate
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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!)
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Mesh Editing
1. Moving the mesh around, without changing its underlying topology (structure)
• Manipulate vertices, edges, faces
• Translate (Move)• Rotate• Scale
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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)
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Poly Boolean operations
• Intersection• Union• Difference• Good for solids• Many animators avoid them
– Messy mesh– Loss of control
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Polygon examples
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GPH 338 Computer Animation Survey
Polygon Texture unwrap Sample
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GPH 338 Computer Animation Survey
NURBS surfacesNon-Uniform Rational B-Spline
Flexible rectangles, bounded by NURBS curves
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NURBS• “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
• 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
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NURBS curves
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
Loft Extrude / Sweep
Revolve / LatheSurface from boundary
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Attaching NURBS Surfaces
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Trimmed NURBS Surface
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NURBS
• 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• 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
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Subdivision Surfaces
• 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
• Good for complicated topology• (This is difficult to make out of rectangles)
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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!
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It will be really useful to use drawings as reference.
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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 …
GPH 338 Computer Animation Survey