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

2. 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

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. 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

10. GPH 338 Computer Animation Survey
Polygon examples

11. GPH 338 Computer Animation Survey
Polygon Texture unwrap Sample

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

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

14. GPH 338 Computer Animation Survey
Flexible rectangles

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

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. Attaching NURBS Surfaces
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. Subdivision Surfaces - Subdivided Polygons
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. 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 …