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Introduction to Modeling

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Introduction to Modeling What is CG Modeling? Combination of Sculpting, Architecture, Drafting, and Painting. The core component of computer animation. – PowerPoint PPT presentation

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Title: Introduction to Modeling


1
Introduction to Modeling
2
What is CG Modeling?
  • Combination of Sculpting, Architecture, Drafting,
    and Painting.
  • The core component of computer animation.

3
What are the challenges Time!
  • Time to create the models.
  • Time to render the models.
  • Time to animate the models.

What are our options?
  • To improve rendering time reduce polygon count.
  • To improve realism increase polygon count.
  • To create models faster reduce polygon count.
  • To reduce animation time reduce number of
    manipulators.
  • To improve animation realism increase the number
    of manipulators.

4
Low polygon model
5
High polygon model
6
Few manipulators
7
Many manipulators
8
How to create models?
  • Hand code the model no one does this anymore.
  • Use a modeling tool eg Maya.
  • Scan physical models using a 3D scanner.

9
Generate by Hand
Pros/Cons Very very exact. You know exactly what
you get. Very very time consuming. Not possible
to build large or Complex models.
10
Use a Modeling Tool - Maya
Pros/Cons Quick to build models. Can build very
complex models Lots of controls and
manipulators Easy to build overly complex
models Tools can be difficult t learn. Can be
difficult to control output. Can be hard to port
to other tools
11
Use a 3D Scanner
Pros/Cons Very quick to build models. Can be
done automatically. Can hire students to do
it. Few controls and manipulators. Requires
extensive re-editing. Generates models with too
many polygons. Limits animators flexibility.
12
What are the Parts of Modeling?
  • Scene when modeling work on a scene at a time.
  • Spaces Where your models sit in space.
  • Objects the primitives used to build your
    models.
  • Structures combine objects to make structures.
  • Operators Tools to build structures from
    objects.

13
Space
Structure
Object
14
Spaces
  • Coordinate Spaces
  • X Y Z
  • Cartesian Coordinates
  • Rectangular Coordinates
  • Global Coordinates
  • Local Coordinates

15
Projections
  • How we go from 3D to 2D
  • Two types Perspective and Orthographic

16
Objects
17
How can you model objects?
  • Polygonal Models.
  • NURBS
  • Subdivision Surfaces
  • Parametric Models
  • Implicit Surfaces

18
Polygonal Models
Pros/Cons Simple to understand. Simple to
render. Simple to combine to make
shapes. Hardware supported rendering Need lots
of polygons for complex shapes. Difficult to
animate lots of polygons. Lots of controls
needed. Advanced modeling operations are
difficult. Continuity problems.
  • Polygonal Models consist of
  • Vertices
  • Edges
  • Faces

Polygon
Vertex
Face
Edge
19
NURB Models
Non-Uniform Rational B-Splines
  • NURBs are made of
  • Patches
  • Curves
  • Control Points

Pros/Cons Need fewer patches for complex
objects. Easier to animate patches. Fewer
controls needed. No Continuity problems. Advanced
modeling operations are easier. Hard to create
corners! Difficult to understand. Difficult to
render. Simple to combine to make shapes. Render
by converting to polygons
20
Subdivision Surfaces
  • Provides Localized Refinement
  • Allows you to mix sharp and smooth corners.
  • Continuity controlled locally.
  • Increased rendering time
  • Requires clear understanding to generate good
    models.
  • Can be difficult to animate.

21
Parametric Models and Implicit Surfaces
Mathematical representations of complex
surfaces. X2Y3-Z4- 12 Xr(t),
Yr(t)2r2(t), Zt Not in production use at
this time. Have very beneficial mathematical
properties. Are extremely difficult to render,
modify, and animate.
22
Structures
23
What Kinds of Modeling Operations Exist?
  • Insert and Delete point, edge, face.
  • Add Polygon/NURB
  • Boolean Operations Union, Intersect, Difference.
  • Advanced Operations
  • Extrude along path.
  • Loft surface
  • Revolve
  • Bend
  • Split
  • Very Advanced Operations
  • Smooth Model

24
What kinds of modeling jobs are there?
  • General Modelers
  • Photo-realistic modelers
  • High poly-count modelers
  • Low poly-count modelers
  • Character Animators
  • Prop Modelers

25
What types of animation controls are available?
  • Simple directly keying specific components.
  • Moderate An I/K skeleton, Solvers.
  • Complex Programmed Mel Scripts, advanced
    solvers. Linked Solvers.

26
How do you control color and appearance.
  • Assign Materials.
  • Assign Shaders.
  • Assign Textures.
  • Advanced Shaders eg Renderman.

27
What about rendering?
  • Everything is translated to Triangles.

28
How do you Triangulate?
  • Polygons
  • NURBS
  • Subdivision Surfaces
  • Parametric Surfaces
  • Implicit Surfaces

29
How is everything rendered.
  • First everything is converted to polygons
  • Second everything is converted to triangles.
  • Then everything is rendered thru the graphics
    pipeline discussed in the prior lecture.

30
Good References
  • 3D Computer Graphics
  • Alan Watt
  • The Art of 3-D Computer Animation and Imaging
  • Isaac Victor Kerlow
  • 3D Animation From Models to Movies
  • Adam Watkins
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