CHS
UCB
Let’s get technical…
Semantics of the Course Title:
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“Solid” “Modeling” (“Procedural” …)
CHS
UCB
What is a Solid ?
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Examples of solids and non-solids:
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What are the key properties of a solid?
CHS
UCB
What is a Solid ?
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Examples of solids and non-solids:
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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?
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Maintains shape in a predictable way
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Has a well-defined surface
CHS
UCB
Modeling -- as in “Describing”
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Why do we create models of solids ?
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What do we want to do with these models ?
CHS
UCB
Modeling -- What is the Purpose ?
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Why do we create models of solids ?
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What do we want to do with these models ?
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For visualization, fabrication, analysis ...
Analyze: mass, momenta, strength, flexibility, beauty,
reachability, assemblability, fluid flow in cavities, ...
What types of models are we interested in ?
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True solid shapes, with orientable 2-manifold surfaces,
mostly rigid, perhaps with predictable deformability;
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and assemblies of such objects.
What is outside scope of CS 285 – Sp.2006 ?
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Collections of polygons that “look like” a forest,
water, clouds, fire, rainbow (--> rendering class)
CHS
UCB
Modeling -- as in “Designing”
Where do such models come from ?
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Some reality capture process
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Some procedural generation process
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e.g., 3D scanning
maximizing/minimizing some functional
(e.g., minimize area as in soap bubbles)
Some creative design process
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realizing some desired functionality
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capturing an aesthetic vision
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( BUT NO RANDOM BLOBS ! )
CHS
UCB
No Random Blobs !
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Many modeling systems are mostly suitable
to make “lumpy potatoes” by moving dozens
of control vertices individually.
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We will concentrate on designed shapes:
These are optimal in some local domain;
any small change would make them inferior.
CHS
UCB
No 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 points
is not in the spirit of CS 285.
CHS
UCB
Make Computer (CAD) Models of:
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Man-made Objects:
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utensils, furniture, machinery, buildings, sculptures, …
(these may have come from CAD models).
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NOT: complete cities, complex vehicles, ...
Natural Objects:
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mountains, sea shells, tree trunks, bones, …
(these allow some procedural generation).
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NOT: animals, forests, hedges, …
Visualization Models of:
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height functions, math surfaces, 4D objects, …
(these can be constructed procedurally).
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NOT: fluid-flow vector fields ...
CHS
UCB
How Do You Do Procedural Design?
Need an Appropriate Programming Language:
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Auto-LISP in AutoCAD
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Other CAD extensions
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Mathematica
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Matlab
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C,C++
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SLIDE (Unigrafix, OpenGL, Tcl) == >
For your course projects you can use whatever
Programming/CAD environment makes you
most productive.
CHS
UCB
The PROs and CONs of SLIDE
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Lies between:
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Mathematica / Matlab and
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Traditional CAD tools (Solidworks, Autocad…)
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Offers interactive fine tuning of critical parameters
via some sliders, gives visual feedback.
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Source code is under our own control.
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Not a properly maintained system.
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Tcl is a pain during the debugging process!
CHS
UCB
Course Projects in CS 285
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Design something that can be fabricated:
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Fancy casing for a wearable computer
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3D visualization model of complex geometry
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Snap-together mechanism
A model to be explored by simulation:
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Strength / sound analysis on a mechanical part
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Manufacturability analysis on an injection mold
The chosen shape should offer some challenges
that can best be overcome
by a small programming effort
which will lead to a usable utility:
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Gear box --> gearwheel generator.
CHS
UCB
Other Possible Course Projects
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Parameterized Objects
that can be fine-tuned and optimized:
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Bells, Sculptures, Mechanisms, Containers,
Puzzles, Mathematical Models, …
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My own projects of current interest:
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Klein’s Quartic surface
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Parameterized Bell
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3D Penrose Tiles
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More later in the course …
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Approach me with your own ideas
as soon as possible.
CHS
UCB
How to Make a CAD Model ?
How would you make a CAD model of:
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a plastic spoon,
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a gear wheel,
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an artistic part,
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a math surface ?
Typically, this is a multi-stage process !
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Study this process in Assignment #1
CHS
UCB
Design of a CAD Model
Multi-stage Design Process:
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Initial Inspiration (Mental Image)
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Clear Concept (Sketch, Mock-up)
(refined by fabrication concerns)
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Precise Part Description (CAD file)
A1
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Fabrication Plan (Machine readable)
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Finished Part (Physical Artifact)
CHS
UCB
Get To Know Each Other !
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Introductions…
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Team Formations
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Work Together !
CHS
UCB
Extras ...
CHS
UCB
What is a Solid ? -- More Answers
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The Abstraction of a “Solid”
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Solids are composed of atoms
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Atoms are mostly empty space
Smoothing and Sampling
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Use a finite-size probe to determine extent of a solid
The Boundary of a Solid
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How far the above probe can go
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Level-set surface of a filtered density function
Why are these considerations relevant ?
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We often make approximations to an ideal shape,
e.g., use triangle mesh to represent a spline patch