Introduction to Modeling: Introduction to Modeling What is CG Modeling?: What is CG Modeling? Combination of Sculpting, Architecture, Drafting, and Painting.
The core component of computer animation. What are the challenges: – Time!: 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. Low polygon model: Low polygon model High polygon model: High polygon model Few manipulators: Few manipulators Many manipulators: Many manipulators How to create models?: 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. Generate by Hand: 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. Use a Modeling Tool - Maya: 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 Use a 3D Scanner: 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. What are the Parts of Modeling?: 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. Slide13: Structure Object Space Spaces: Spaces Coordinate Spaces
X Y Z
Local Coordinates Projections: Projections How we go from 3D to 2D
Two types: Perspective and Orthographic Objects: Objects How can you model objects?: How can you model objects? Polygonal Models.
Implicit Surfaces Polygonal Models: Polygonal Models Polygonal Models consist of:
Faces Edge Face Vertex Polygon 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. NURB Models: NURB Models NURBs are made of:
Control Points Non-Uniform Rational B-Splines 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
Subdivision Surfaces: 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.
Parametric Models and Implicit Surfaces: Parametric Models and Implicit Surfaces Mathematical representations of complex surfaces.
X^2*Y^3-Z^4- 12 X=r(t), Y=r(t)+2*r^2(t), Z=t
Not in production use at this time.
Have very beneficial mathematical properties.
Are extremely difficult to render, modify, and animate. Structures: Structures What Kinds of Modeling Operations Exist?: What Kinds of Modeling Operations Exist? Insert and Delete point, edge, face.
Boolean Operations: Union, Intersect, Difference.
Extrude along path.
Very Advanced Operations
Smooth Model What kinds of modeling jobs are there?: What kinds of modeling jobs are there? General Modelers
High poly-count modelers
Low poly-count modelers
Prop Modelers What types of animation controls are available?: 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. How do you control color and appearance.: How do you control color and appearance. Assign Materials.
Advanced Shaders – eg Renderman. What about rendering?: What about rendering? Everything is translated to Triangles. How do you Triangulate?: How do you Triangulate? Polygons
Implicit Surfaces How is everything rendered.: 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. Good References: Good References 3D Computer Graphics
The Art of 3-D Computer Animation and Imaging
Isaac Victor Kerlow
3D Animation: From Models to Movies