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GPH 338 Computer Animation Survey

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

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  1. GPH 338 Computer Animation Survey GPH 338Computer Animation Survey Poly/NURBS/Subdiv --Winny

  2. 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

  3. GPH 338 Computer Animation Survey Polygons Polygonal surfaces (Mesh)

  4. GPH 338 Computer Animation Survey Polygons are made up of several components: Vertices Edges Faces UVs

  5. GPH 338 Computer Animation Survey Polygon Primitives • Standard • Parametric – can vary their attributes vertices, edges, faces, subdivlevel… • Use them when appropriate

  6. 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!)

  7. 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

  8. 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)

  9. GPH 338 Computer Animation Survey Poly Boolean operations • Intersection • Union • Difference • Good for solids • Many animators avoid them • Messy mesh • Loss of control

  10. GPH 338 Computer Animation Survey Polygon examples

  11. GPH 338 Computer Animation Survey Polygon Texture unwrap Sample

  12. GPH 338 Computer Animation Survey NURBS surfaces Non-Uniform Rational B-Spline Flexible rectangles, bounded by NURBS curves

  13. “Flexible Rectangles” Smooth Made by Isoparms U V Manipulated by Few points (CV) GPH 338 Computer Animation Survey NURBS

  14. GPH 338 Computer Animation Survey Flexible rectangles

  15. GPH 338 Computer Animation Survey NURBS surfaces bounded by NURBS curves

  16. 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

  17. 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

  18. GPH 338 Computer Animation Survey NURBS Primitives • Standard • Parametric – can vary their attributes • # of isoparms, Hull, control vertices, etc. • Use them when appropriate

  19. GPH 338 Computer Animation Survey Surfaces from Curves Extrude / Sweep Loft Surface from boundary Revolve / Lathe

  20. GPH 338 Computer Animation Survey Attaching NURBS Surfaces

  21. GPH 338 Computer Animation Survey Trimmed NURBS Surface

  22. 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

  23. 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 ($!)

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

  25. GPH 338 Computer Animation Survey Subdivision Surfaces • Subdivide polygons • Hierarchy of polygons • Manipulate at different levels

  26. GPH 338 Computer Animation Survey Poly to Subdiv examples

  27. GPH 338 Computer Animation Survey SubDiv Surface

  28. GPH 338 Computer Animation Survey Subdivision Surfaces • Good for complicated topology • (This is difficult to make out of rectangles)

  29. 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!

  30. GPH 338 Computer Animation Survey It will be really useful to use drawings as reference.

  31. 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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