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Let’s get technical…. Semantics of the Course Title: “Solid” “Modeling” (“Procedural” …). What is a Solid ? . Examples of solids and non-solids: What are the key properties of a solid?. What is a Solid ? . Examples of solids and non-solids: YES: a block of steel, wood, styrofoam
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Let’s get technical… Semantics of the Course Title: • “Solid” “Modeling” (“Procedural” …)
What is a Solid ? • Examples of solids and non-solids: • What are the key properties of 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
Modeling -- as in “Describing” • Why do we create models of solids ? • What do we want to do with these models ?
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)
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 ! )
No 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.
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 pointsis not in the spirit of CS 285.
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 ...
How Do You Do Procedural 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.
The 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!
Course 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 asmall programming effortwhich will lead toa usable utility: • Gear box --> gearwheel generator.
Other 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.
How 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
Design 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
Get To Know Each Other ! • Introductions… • Team Formations • Work Together !
What 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
