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Chapter 3

IAT 343 Chapter 3: Modeling Concepts


Department
Interactive Arts & Tech
Course Code
IAT 343
Professor
Steve DiPaola
Chapter
3

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WK1:Chapter3
April19,2018 8:00PM
Chapter3ModelingConcepts:Pg.93‑114
3.1Space,Objects,andStructures
Right‑handedorleft‑handedCoordinateSystem93
• Masonsandarchitectshavedevelopedconventionssothatthey
canbepreciseandclearaboutmeasuringspaces,building
objects,andarrangingtheminstructures
Right‑handedcoordinatesystem:thevaluesonthexaxis
becomelargertotherightoftheorigin,thevaluesontheyaxis
increaseastheymoveabovetheorigin,andthevaluesonthez
axisgrowastheygetclosertous
Left‑handedcoordinatesystem:thevaluesonthezaxis
decreaseastheygetclosertous
• Severalvariationsofthedirectionalityoftherectangular
coordinatesystem,most3dsystemsusetheright‑handed
coordinatesystemtodescribethevirtualworld
• 3axesintherectangularcoordinatesystem:
1. Frontplane‑xyaxes
2. Topplane–xzaxes
3. Sideplane–yzaxes
Spherical/azimuthalcoordinatesystemprovidesasimple
methodforplacingobjectsina3dworldintermsoftheir
distancetotheobject,theiranglearoundthepointofinterest,
andtheiraltitudeangleabovethepointofinterest
Sphericalsystemisusefulforplacingandmovingcameraand
lightingsourcesina3dscene
World/globalcoordinatesystemfocusesonplacingormoving
objectsintheworldinrelationtoeachother
• Worldcoordinatesareabsolutevaluesthatarerelativetothe
originoftheworld
○ Donotdependonanyspecificobjectintheworld
○ Appliestoallobjectsintheworldindistinctly
• Eachobjectintheworldcanhaveitsownobject/local
coordinatesystem(valuesrelativetotheoriginoftheobject,
sometimesplacedatthecenteroftheobject)
3.3Vertices,Edges,andFacets
Polygon98
• 3dobjectsaredefinedbypoints,lines,edges,places/facets
• Points,lines,andfacetsarethebasicelementsthatcanbeused
tobuild3dobjects
Point–easilydefinedbyitsxyzlocation
Line–definedbythexyzlocationofitstwoendpoints
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