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UCBUCB Let’s get technical…Let’s get technical…

Semantics of the Course Title:

“Solid” “Modeling” (“Procedural” …)

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UCBUCB What is a Solid ? What is a Solid ?

Examples of solids and non-solids:

What are the key properties of a solid?

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UCBUCB What is a Solid ? What is a Solid ?

Examples of solids and non-solids: YES: a block of steel, wood, styrofoam

NO: clouds, liquids,

?: a flexible wire, a rubber gasket, cloth ...

What are the key properties of a solid? Maintains shape in a predictable way

Has a well-defined surface

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UCBUCB Modeling -- as in “Describing”Modeling -- as in “Describing”

Why do we create models of solids ?

What do we want to do with these models ?

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UCBUCB Modeling -- What is the Purpose ?Modeling -- What is the Purpose ?

Why do we create models of solids ? For visualization, fabrication, analysis ...

What do we want to do with these models ? Analyze: mass, momenta, strength, flexibility, beauty,

reachability, assemblability, fluid flow in cavities, ...

What types of models are we interested in ? True solid shapes, with orientable 2-manifold surfaces,

mostly rigid, perhaps with predictable deformability;

and assemblies of such objects.

What is outside scope of CS 285 – Sp.2006 ? Collections of polygons that “look like” a forest,

water, clouds, fire, rainbow (--> rendering class)

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UCBUCB Modeling -- as in “Designing”Modeling -- as in “Designing”

Where do such models come from ?

Some reality capture process e.g., 3D scanning

Some procedural generation process maximizing/minimizing some functional

(e.g., minimize area as in soap bubbles)

Some creative design process realizing some desired functionality

capturing an aesthetic vision

( BUT NO RANDOM BLOBS ! )

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UCBUCB NoNo Random Blobs ! Random Blobs !

Many modeling systems are mostly suitable to make “lumpy potatoes” by moving dozens of control vertices individually.

We will concentrate on designed shapes:These are optimal in some local domain;any small change would make them inferior.

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UCBUCB NoNo Warped Quadrilaterals Warped Quadrilaterals

A single Bézier patch or rectangular B-spline array does not make a solid.

Again, there should be an element of “DESIGN.”Just randomly moving all control pointsis not in the spirit of CS 285.

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UCBUCB Make Computer (CAD) Models of:Make Computer (CAD) Models of:

Man-made Objects: utensils, furniture, machinery, buildings, sculptures, …

(these may have come from CAD models).

NOT: complete cities, complex vehicles, ...

Natural Objects: mountains, sea shells, tree trunks, bones, …

(these allow some procedural generation).

NOT: animals, forests, hedges, …

Visualization Models of: height functions, math surfaces, 4D objects, …

(these can be constructed procedurally).

NOT: fluid-flow vector fields ...

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UCBUCB How Do You Do How Do You Do ProceduralProcedural Design? Design?

Need an Appropriate Programming Language:

Auto-LISP in AutoCAD

Other CAD extensions

Mathematica

Matlab

C,C++

SLIDE (Unigrafix, OpenGL, Tcl) == >

For your course projects you can use whatever Programming/CAD environment makes you most productive.

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UCBUCB The PROs and CONs of SLIDEThe PROs and CONs of SLIDE

Lies between:

Mathematica / Matlab and

Traditional CAD tools (Solidworks, Autocad…)

Offers interactive fine tuning of critical parameters via some sliders, gives visual feedback.

Source code is under our own control.

Not a properly maintained system.

Tcl is a pain during the debugging process!

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UCBUCB Course Projects in CS 285Course Projects in CS 285

Design something that can be fabricated: Fancy casing for a wearable computer 3D visualization model of complex geometry Snap-together mechanism

A model to be explored by simulation: Strength / sound analysis on a mechanical part Manufacturability analysis on an injection mold

The chosen shape should offer some challengesthat can best be overcome by a small programming effort which will lead to a usable utility: Gear box --> gearwheel generator.

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UCBUCB Other Possible Course ProjectsOther Possible Course Projects

Parameterized Objects that can be fine-tuned and optimized:

Bells, Sculptures, Mechanisms, Containers,Puzzles, Mathematical Models, …

My own projects of current interest: Klein’s Quartic surface

Parameterized Bell

3D Penrose Tiles

More later in the course …

Approach me with your own ideas as soon as possible.

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UCBUCB HowHow to Make a CAD Model ? to Make a CAD Model ?

How would you make a CAD model of:

a plastic spoon,

a gear wheel,

an artistic part,

a math surface ?

Typically, this is a multi-stage process !

Study this process in Assignment #1

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UCBUCB Design of a CAD ModelDesign of a CAD Model

Multi-stage Design Process:

Initial Inspiration (Mental Image)

Clear Concept (Sketch, Mock-up)(refined by fabrication concerns)

Precise Part Description (CAD file)

Fabrication Plan (Machine readable)

Finished Part (Physical Artifact)

A1

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UCBUCB Get To Know Each Other !Get To Know Each Other !

Introductions…

Team Formations

Work Together !

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UCBUCB Extras ...Extras ...

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UCBUCB What is a Solid ? -- More AnswersWhat is a Solid ? -- More Answers

The Abstraction of a “Solid” Solids are composed of atoms

Atoms are mostly empty space

Smoothing and Sampling Use a finite-size probe to determine extent of a solid

The Boundary of a Solid How far the above probe can go

Level-set surface of a filtered density function

Why are these considerations relevant ? We often make approximations to an ideal shape,

e.g., use triangle mesh to represent a spline patch