au09_speakerhandout_dv9210-2

8/3/2019 AU09_SpeakerHandout_DV9210-2

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Parametric Design Modeling with Autodesk 3ds

MaxDavid Fano CASE Design, Inc - www.case-inc.com

DV9210-2This presentation will show how to use 3ds Max modeling tools to build iterative parametricdesign systems. In this session, we will cover 3ds Max geometry types (Editable Mesh, Poly, Patch andNURBS), combine modifiers to build complex systems, use wire parameters to quickly make geometricpatterns, and provide an introduction to MAXScript. In this session, you will learn to reduce the amount ofexplicit modeling, and instead build flexible design systems so you can focus more effort on design.

About the Speaker:

David Fano established CASE Design in 2008. He previously worked at SHoP Architects, where he was Director ofTechnology Research. At CASE, David has been responsible for managing the implementation of BuildingInformation Modeling (BIM) at leading architecture and construction firms. He has also lead and managed industrypartnerships with leading service providers and software vendors. His project experience at CASE has included TheNational Museum of African American History and Culture competition with Diller Scofidio+ Renfro, and The MiamiScience Museum with Grimshaw Architects. David has been an Adjunct Professor at Columbia University's Graduate

School of Architecture, Planning, and Preservation where he teaches seminars and workshops focusing on theimpact of technology on design processes. David received his Master of Architecture with honors from ColumbiaUniversity where he was the recipient of the Lucille Smyser Lowenfish Memorial Prize and the Computer AidedDesign Honor Award

[email protected]


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Parametric Design Modeling with Autodesk 3ds Max

2

This Class will cover the following topics

GeometryTypes

ParametricModeling

ModelingParametricWalkway

ModelingParametricTower


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Geometry Types

ConceptsPoints

Figure1:Pointtypesin3dsMax

Pointsareoneofthemostbasicgeometricelementsandthefoundationofmostprimitive

geometrictypes.Pointsarerepresentedbyanorderedsequenceofnumbers(coordinates),

conventionallyrepresentedas(x,y)fortwodimensionalspaceand(x,y,z)forthreedimensional

space.3Dmodelingapplicationsprovideaccesstopointsinavarietyofways.Inmostexplicit

modelingapplications,pointsarerarelydefineddirectly;instead,theyaredefinedimplicitlyby

creatingothergeometricobjects.Oncecreated,however,theseapplicationsoftenprovide

accesstopointsthroughsubobjectselectionorpropertiesofthebaseobject;forexample,the

VertexsubobjectselectioninAutoCAD2010,Autodesk3dsMax2010,andAutodesk

Maya2009software.Parametricmodelingapplicationsoftenusepointsmoredirectly,giving

userscontroloverthewayapointisdefinedandcontrolled,whichisthenusedasthebasisof

othergeometric

operations;

for

example,

the

point

object

in

the

new

Conceptual

Mass

environmentofAutodeskRevitArchitecture2010.Pointcoordinatesareacriticaland

frequentlyusedgeometricpropertyforarchitecturaldesign,astheyoftenserveasthebasisof

informationexchangebetweenvariousmodeling,analysis,andfabricationapplications.

Curves

Figure2:Curvetypesin3dsMax

Curvesarefundamentalgeometricelementsfordesignand3Dmodeling.Curvescanbe


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generalizedmathematicallyasacontinuousseriesofconnectedpoints.Therefore,straight

lines,circles,helixes,andconicsectionsarealltypesofcurves.Curvescanbedefinedand

representedmathematicallyinavarietyofwaysincludingparametrically,explicitly,and

implicitlywith

various

3D

modeling

applications,

giving

users

different

access

to

these

methods.

Furthermore,curveshavenumerouspropertiesthatcanbeaccessedandusedby3Dmodeling

applicationssuchaslength,direction,area,tangency,curvature,radius,andpoints.Inaddition

tothecurvetypesmentionedabove,most3Dmodelingapplicationsprovideaccesstofreeform

curvessuchasBezier,Bspline,andNURBS.Followingtheinventionofthesecurvetypesinthe

1950s,freeformcurvescanbecontrolledpreciselyusingrelativelyfewpointsthatcreatea

controlpolygonfromwhichacurveisderived.NURBS(nonuniformrationalBspline)curvesoffertheadditionalshapeparameterofweights,whichenableuserstomodifythelocal

influenceofeachcontrolpointontheshapeofthecurve.Bsplinecurvesareaspecialcaseof

NURBScurvesinwhichallweightsareequal.BsplinecurvesarecompositeBeziercurvesthat

have

the

same

tangent

and

same

curvature

at

the

connecting

points.

Autodesk

Maya

2009

offerscomprehensivecreationandeditingtoolsforNURBScurves,whileAutoCAD2010,3ds

Max2010,andRevitArchitecture2010allsupportNURBS,butofferfewerwaystocreateand

manipulatethem.

Surfaces

Figure3:Surfacetypesin3dsMax

Theabilitytocreateandmodifysurfacesisakeyfeatureofany3Dmodelingapplication.

Traditionalsurfaceclassessuchasextrusion,translational,rotational(surfacesofrevolution),

andruledarecreatedbysmoothlysweepingasingleprofilecurveonoraroundanothercurve.

Cylinders,cones,spheres,tori,ellipsoids,paraboloids,hyperboloids,helicoids,andvarious

othersurfacesfallwithintheseclasses.Thesesurfaceshavenumerouspropertiesthatsimplify

theprocess

of

rationalization

into

repeatable

planar

elements,

so

they

are

frequently

used

for

architecturaldesign.Yet,therearenumerousshapesthatcannotbecreatedusingthese

traditionalsurfaceclasses,thereforeitisnecessaryfor3Dmodelingapplicationstosupport

freeformsurfaces,mostcommonlyinone(ormore)ofthesethreetypes:Beizer/B

spline/NURBSSurfaces,meshes,andsubdivisionsurfaces.


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Beizer,Bspline,andNURBSsurfacesarebasedonthesamemathematicalprinciplesastheir

curvecounterparts,withasimplifiedcontrolmeshmadeupofrowsandcolumnsofquadrilateralpolygonsfromwhichasmoothsurfaceisderived.Also,likecurves,themain

differencebetween

B

spline

and

NURBS

surfaces

is

the

ability

to

modify

the

weight

parameter

ofindividualcontrolpointsofaNURBSsurface.NURBShavebecomethestandardsurfacetype

withintheproduct,aeronautical,andautomotiveindustrieswhereprecisecontrolover

tangency,curvature,andsurfacecontinuityareaprimaryconcern.Butduetothecosts

associatedwithbuildingthesesmoothlycurvedsurfacesforlarge,oneoffarchitectural

projects,NURBSsurfacesarerarelyuseddirectlyinarchitecture.Inmostcases,thesesmooth

surfacesarerationalizedintopanelsorwireframeedges,withconcernsofplanarityand

repetitionoftendeterminingtheapproachtorationalization.Thisiswherepolygonmeshesare

useful.

Meshesare

essentially

ordered

collections

of

points

(vertices)

that

are

connected

by

polygons

(faces).Thesefacesaretypicallytrianglesorquadrilaterals,butotherpolygonsarepossible.By

varyingthesize,shape,anddensityofpolygonfaces,thesemeshescanbemadeto

approximatelyrepresenttheshapeofasmoothsurface.Meshmodelsmuststorethe

connectivity(meshtopology),whichistherelationshipbetweentheverticesandfaces,the

orderofwhichdeterminesthedirection,ornormal,oftheface.Allmeshesmadeoftriangles

haveplanarfaces,whilethesameisnottrueofquaddominantmeshes,althoughcertain

classesofquadrilateralmeshesareplanarandthereforelendthemselvestoarchitectural

rationalization.Finally,andmostimportantly,meshesareusedinvirtuallyallaspectsof

computationalgeometryfromvisualizationtoanalysis.Maintainingcontroloverthemesh

representation

of

complex

geometry

becomes

extremely

important

when

dealing

with

analysis

applicationsthatusemeshesforfiniteelement(FEM),computationalfluiddynamics(CFD),or

thermodynamiccalculations.

DespitetheflexibilityofbothNURBSandmeshapproachestodefiningfreeformsurfaces,there

remaincertainshapesthataredifficulttoachievewithregularmeshesorcontrolpolygons.This

iswheresubdivisionsurfacescomein.Subdivisionsurfaceswereinitiallycreatedforusein3D

animatedfeaturefilms.Theprocessofcreatingasubdivisionsurfaceinvolvesmultiplelevelsof

refinementofacoarsemesh,untilthedesiredlevelofsmoothness(whichcanachievethatofa

Bsplinesurface)orfacesize(inarchitecturalapplications)hasbeenreached.Thereare

numerous

subdivision

algorithms

available

and

3D

modeling

applications

often

provide

access

tomorethanone.ThethreemostcommonapproachesareDooSabin,CatmullClark,and

Loop,whichareallnamedaftertheirinventors.BothDooSabinandCatmullClarkrelyupon

quadmeshes,withCatmullClarkproducingsmootherresultsthatarefurtherawayfromthe

initialcontrolmesh.Loopsubdivisionutilizesandproducestriangularmeshes.Although

subdivisionsurfacemodelinghasmadeitswayintoarchitecturaldesignviaanimationtools

usedbyarchitects,theirutilityislimitedduetothelackofcontrolovertheresultsofthe

smoothingalgorithms.Therefore,geometrycreatedthroughthisprocessisoftenremodeledor


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convertedintoeitherNURBSormeshsurfacesforrationalization.

RevitArchitecture2010providestoolstocreateandmodifyBsplinesurfacesandsupports

NURBSsurfacescreatedinotherapplications.Additionally,thenewpatterningtoolsgiveRevit

userstheabilitytobreaksmoothsurfacesdownintopolygons.Maya2009isprimarilyaNURBS

surfacemodeler,withsomesupportforbothmeshandsubdivisionsurfacemodeling.AutoCAD

2010isprimarilymeshbased,withthenewfreeformmodelingtoolsaddingnewsubdivision

surfacecreationandeditingtools.3dsMax2010isalsoprimarilymeshbased,withthenew

GraphiteModelingtoolsbuildinguponanalreadystrongbaseofpolygonmeshcreationand

manipulationtools.3dsMaxalsosupportssubdivisionsurfaces,buthaslimitedsupportfor

NURBSsurfaces.


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Parametric Modeling

Concepts

SolidModeling

Figure1:Differentiationbetweensolidmodelingandsurfacemodeling

SolidModelingisatechniqueincomputeraideddesign(CAD)thatallowsforthe

representationof

solid

objects.

Its

primary

uses

are

for

fields

such

as

architectural

design,

engineeringanalysis,computergraphics,animation,productvisualization,andrapid

prototyping,amongotherthings.Originally,solidmodelingsoftwareusedoneoftwomethods

todefinesolidshapes,eitherconstructivesolidgeometry(CSG)orboundaryrepresentation(B

REP).CSGusessolidprimitivessuchasrectangularprisms,spheres,cylinders,andcones,and

booleanoperationssuchasunions,subtractions,andintersectionstocreateasolidmodel.B

REPmethods,ontheotherhand,beginwithoneormorewireframeprofilesandgeneratea

solidmodelthroughoneofvariousprocessessuchasextrusion,sweeping,revolving,or

skinning.Additionally,solidscanbeconstructedthroughasewingoperation,whichisaprocess

ofcombiningsurfacesthatoftenhavecomplexshapes.Becauseeachofthesesolidmodeling

processeshave

their

own

advantages

and

limitations,

it

is

often

most

beneficial

to

generate

solidmodelsusingacombinationofbothCSGandBREPtechniques.Autodeskapplicationsuse

ahybridofthesetechniqueswithAutoCAD2010andAutodeskRevitArchitecture2010

providingnativesupportforsolidmodeling.ModelscreatedbysewingsurfacesinAutodesk

3dsMax2010andAutodeskMaya2010canbeexportedasDWGfilesandconvertedto

solidsusingAutoCAD2010.


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ParametricModeling

Figure2:Preciselycontrolledmodificationofaparametricgeometry

Aparameter,initsmostgeneralsense,definesasystemanddeterminesthelimitsand

performanceofthesystem.AfeatureofsomeCADapplicationsistheabilitytoconstructa

modelparametrically.Withinaparametricmodel,eachentitysuchasaprimitivesolid,aline,or

filletoperationpossessesassociatedparameters.Theseparameterscontrolthevarious

geometricpropertiesoftheentitysuchasitslength,width,height,radius,andsoon.Theyalso

controlthelocationsoftheseentitieswithinthemodelandhowentitiesrelatetooneanother.

Forexample,geometricentitiescanbelocatedattheoriginofacurve,themidpointofaline,

orthevertexofaface.Additionally,theparameterscanbeadjustedbytheoperatoras

necessarytocreatethedesiredgeometry.Thisprocessisknownasparameterizationandis

essentially

the

specification

of

a

point,

curve,

or

surface

by

means

of

one

or

more

variables

that

takeonvaluesinauserspecifiedrange.Parametricmodelingissignificantforconceptual

designbecauseitenablesdesignstobemodifiedandcontrolledprecisely,aslongasthese

modificationsarewithinthelimitsofthesystem.RevitArchitectureprovidesacomprehensive

setofparametricmodelingtools,whilebothMayaand3dsMaximplementparametric

behaviorbasedonconstructionhistory.AutoCADprovidesanewparametricdrawing

environmentthatallowsforthecreationof2Dgeometricanddimensionalconstraintsand

relationships,inadditiontodynamicblocks.


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FeatureBasedModeling

Figure3:Applicationofafilletfeaturetogeometry,atechniqueusedwithfeaturebasedmodeling.

Inthelate1980s,softwaredevelopersbeganimplementinghigherlevelsofabstractiontosolid

modelingconstructiontechniques.Thesetechniquesbecameknownasfeaturebasedsolid

modeling.AfeaturebasedmodelerisaCADapplicationthatenablesdesignersofvariousfields

todefineshapesusinggeometricfeaturesasopposedtoCSGorBREPtechniques.Ageometric

featureisahigherorderCADentity;forexample,operationssuchasplacingholesorfilleting

aretreatedasobjectsthatcanbeupdated,notonetimeoperations.Additionally,parametric

featurebasedmodelingpackagesusehistorytoretaininformationaboutthebuildingprocess

ofthemodel,aswellasexpressionstoconstrainassociationsamongthegeometricentities.

Thisoptionandabilitytoregeneratethemodel'sBREPbaseduponchanges,enablestheuser

to

make

a

modification

at

any

state.

Mechanical

design

applications,

such

as

Autodesk

Inventor,usefeaturebasedmodelingextensively.Autodesk3dsMaxprovidesgeometric

modifiersthatcanbelayeredorstackedonobjectstoachievefeaturebasedbehavior.

Althoughnotsupporteddirectly,bothMayaandRevitArchitecturecanachievefeaturebased

behaviorbylayeringparametricandhistorybasedmodelingoperations.Currently,AutoCAD

doesnotprovidesupportforfeaturebasedmodeling.


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Modeling a Parametric Tower

Overview

In this lesson, we will explicitly model a geometrically complex tower. You will learn how to layer

modeling operations and levels of detail in response to design criteria. The towers form is

constructed directly by manipulating the vertices, edges, and faces of the base geometry and

enabling subdivision surfaces. You will also learn the techniques of extracting geometry from

the tower to develop the building's structure and skin.

Exercise1:ContextandSiteProfile

Figure1:

Site

boundary

within

context.

Itisimportantthattheboundaryofthesite,aswellasthefootprintofthebuilding,have

contextualrelevance.Thissiteboundarywascreatedbydrawingalinesegmentandconnecting

itsstartpointandendpoint,formingaclosedspline.Inordertomaximizespaceforthe

allotmentofprogram,weusethesiteboundaryasthefootprintofthebuilding.


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Exercise2:MassExtrusion

Inthisexercise,youwilllearnhowtocreateasolidbuildingmassfromaclosedsplinethrough

the

process

of

extrusion.

Figure2:Initialbuildingmassconstructedviaextrusionbaseduponthesiteboundary.

Extrudingasplinecreatesaclosedelementcomposedofpolygons.Whenapolygonis

extruded,itmovesnormaltothebaseprofilewhilecreatingnewpolygonsthatformthesides

oftheextrusion,connectingthenewobjecttothebaseprofile.Thisisaneasywaytotransition

fromatwodimensionaldrawingtoathreedimensionalobjectandbeginscreatingaformina

threedimensionalenvironment.OnceasplinehasbeenextrudedintheZdirectionanda

threedimensionalobjecthasbeencreated,inthiscase,abuildingmass,thatobjectcanbe

manipulatedthroughvariousoperationsintheX,Y,andZdirectionstocreateaunique

geometricform.Forthebuildingmass,thesiteboundarywasextrudedtocreatealowerlevel

ofcommercial

space.

To

maintain

street

walls

with

the

existing

context,

this

lower

level

will

be

extrudedtomatchtheheightofthesurroundingbuildings.


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Exercise3:SubObjectManipulation

Inthisexercise,youlearnhowtodirectlymanipulatethegeometryofabuildingmassusing

sub

objects.

Figure3:Processanddevelopmentofmanipulationtothebuildingmassatthesubobjectlevel.

Oncethesolidbuildingmasshasbeencreated,wecannowselectanddirectlymanipulateits

varioussubobjectattributes;thatis,vertex,edge,border,orpolygon.AttheVertexsubobject

level,we

can

select

single

and/or

multiple

vertices

and

move

them

in

space.

Because

vertices

definethestructureofothersubobjects,suchasedgesandpolygons,anymovementorediting

oftheirpositioningwillaffecttheconnectedsubobjectsaswell.AttheEdgesubobjectlevel,

youcanselectsingleand/ormultipleedgesandmanipulatethemthroughstandardmethods

suchastranslate,rotate,andscale.

Becauseweareconceptuallydesigningaformthroughgeometricmanipulation,anddonot

wanttobeinhibitedbynumericprecision,wewillcreatetheformofourtowerthrough

extrudingpolygonsandmovingverticesandedgesuntilwearriveatanoverallformthatweare

pleasedwith.Keepinginmindthepositioningofthebuilding,aswellasitscontextuallocation,

wewillextrudethepolygonclosesttotheoceanandmakethatthebasisofthewaterfront

tower,therebymaximizingoceanviewsaswellascreatingabackcourtyardthatintegrateswith

theexistingparkandlandscape.


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Exercise4:ImplementPrecision

Inthisexercise,youwilllearnhowtoimplementmethodsoflocalprecisionusingthe

Constraint

and

Snap

features.

Figure4:Processanddevelopmentofimplementingprecisionanditsramificationsontheoverallgeometricform

Tofurtherthedevelopmentofourconceptualbuildingdesign,andtoenhanceeaseofuse,

implementing

methods

of

local

precision

can

be

extremely

beneficial.

Two

specific

features

that

areveryusefularetheConstraintandSnapfeatures.Standardsnapsgiveyouadditionalcontrol

increating,translating,rotating,andscalingobjectsandsubobjects,andcanbecombinedwith

freepositioning,whereconstraintsareusedtospecifylimitationsinthepossiblemovementsof

thoseobjectsinspace.Theuseoftheseprecisionfeatureswillenableyoutoachievetheexact

formyoudesirewithgreatereasebecauseoftheadditionalcontrolitprovides.


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Exercise5:InformationExtractiontoCreateGeometry

Inthisexercise,youlearnhowtoextracttwodimensionalinformationfromyourbuilding

mass.

Figure5:Processofarrayingasectioncutandconvertingthatplanarinformationintousefulsolidgeometry

Twodimensionalinformationextractedfromathreedimensionalobjectcanbeusedasa

referenceforfurthermodeldevelopment.Toputthisideaintoaction,sectioncutscanbe

generatedfromathreedimensionalmodelandarrayedinanequidistantfashiontocreate

splinesthatwillbeusedasthebasisofthreedimensionalfloorslabs.Liketheoriginalbuilding

mass,thefloorslabsarecreatedbyextrudingtheclosedsplinesofthesectioncuts,

transformingthem

from

simple

lines

to

athree

dimensional

solid.

This

is

auseful

technique,

particularlyinrespecttoconceptualdesignwithinarchitecture,asitallowsforaquickmethod

forextractingplanarinformationfromamodel,aswellastheabilitytoapplyaspecific

operationtomorethanoneelementatatime.


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Exercise6:ReuseGeometry

Inthisexercise,youlearnhowtoisolateandeditspecificgeometryfromyourbuildingmass.

Figure6:

Isolated

faade

geometry

that

will

be

further

manipulated

to

articulate

structure

and

enclosure.

Reusinggeometryisanimportantskillinthreedimensionalmodelingbecauseitenablesusto

isolatespecificareasofourthreedimensionalmodelandapplytransformationsonalocal,as

opposedtoglobal,scale.Inthiscase,wewillbeusingthisfeaturetoisolatethesidesofthe

towerthatwewillusetoaddstructuralandenclosureelementsinlaterexercises.Basedupon

thetower'sgeographicallocationandorientation,aswellassolarpositioning,wehavechosen

toisolateboththesouthandeastelevationstoaddstructureandcladding.Toisolatethese

facesfromtherestofthemass,weneedtoselectandthenextractthem.Oncethefaceshave

beenextractedfromthemainbuildingmass,theyarereadytobemodifiedusingadditional

operations.


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Exercise7:DefineStructure

Inthisexercise,youlearnhowtocreatebuildingstructure.

Figure7:Processanddevelopmentofdefiningastructuralpatternandconvertingitintosolidgeometry.

Thereareavarietyofwaystoexplicitlydesignandmodelstructuralelements.Wewillbegin

thisprocessbycreatingagridthatcanbeusedasabasisfordesigningthestructure.Forthe

tower,wewillcreateaverticalstructuralsystemthatisbasedoffofafaceted,angularpattern.

Wewilldrawthispatternexplicitlythroughtheprocessofcuttingfaces,basedonthis

underlyinggrid.Inthepreviousexercise,weisolatedthefacesofthesouthandeastelevations.

Wewillusethepatternasareference,cuttingthesefaceswithangularverticalelementsthat

createatriangulatedstructuraldesign.Tothencreatepanelsoutofthesetriangulatedfaces,

wesimplyoffsetthefacestocreateafaceandthenextrudetogivethestructurethickness.


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Exercise8:DesignanEnclosure

Inthisexercise,youlearnhowtocreateapatternforabuilding'senclosure.

Figure8:Detailingfaadedesignatthelocallevelandcompilingallgeometricalsetstoformcompleteddesign.

Likethestructuralpatterns,thereareavarietyofwaystodesignandmodelpatternsfora

building'sskin.Tomaintainaconsistentdesignmethodology,wewillagainusetheprocessof

cuttinggeometrytocreateafacetedenclosuresystem.Unlikethelargegesturesofthe

structure,wecanmanysmallermovesfortheenclosure,asitrequiresagreaterlevelofdetail.

Onceyouhavearrivedatthelevelofdetailthatyoudeemappropriate,mirrortheprocessthat

weusedtodefinethestructuretocreatethisenclosuresystem.Thefacessimplyneedtobe

offsetandextruded.

Afurtherlevelofdesigndetailingcanbeaddedatthisstagebytransformingthiscladdingfrom

ameshtoasubdivisionsurface.Thisconvertstheoriginalcoursefacetingoftheenclosure

systemintoasmoothtopology.


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Bridge Parametric Design

Overview

In this lesson, we will use parametric and associative modeling to create various configurations

for the design of a bridge. The following exercises address a secondary phase of the design

process where iterative variations on individual geometric concepts are needed. Custom

parameters can be created, and used with associative history, for rapid regeneration of

modeling procedures in order to refine ideas.

Exercise1:CreateaSolidGeometricObjectfromaSpline

Inthisexercise,youlearnhowtouseasplineasabasereferencetocreatesolidgeometry.

Figure1:Processandgeneratinganassociativelylinkedsolidgeometryfromaspline

Themodel

that

we

will

create

in

this

lesson

is

aparametric

bridge.

The

initial

geometry

is

generatedfromasplinethatyouintuitivelysketch.Tocreateasurfacefromthespline,wefirst

extrudeitinthepositiveZdirection.Followingthis,wewillselectthesurfaceandoffsetit,

transformingitfromasurfacetoathreedimensionalsolid.Becauseofhistory,any

manipulationsthatwemaketothebasesplinewillaffectoursolidaswellbecausethesolidis

associativelylinkedtothespline.


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Exercise2:ReferencingGeometryInthisexercise,youlearnhowtocreategeometrythroughtheprocessofreferencing.

Figure2:Creatingadditionalassociativelylinkedgeometryfromthebasespline.

Creatingareference,baseduponaselectedpieceofgeometry,isaformofcopyingthat

maintainsassociativitytotheoriginalelement.Thefirstcaseinwhichreferencinggeometry

becomesusefulisintheconstructionofthebridgerailings.Becausethebasesplineisthe

foundationfortheparametricbridge,wewanttoensurethatallgeometricobjectsarebased

uponthisspline.Toinsurethis,weneedtomakereferencesofthesplineandthenusethose

referencestogeneratetheadditionalobjects.Thiswillguaranteethatallgeometriespossess

thesamebasicattributesandarelinkedtoformareferentialsystem.


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Exercise3:AddParametricVariabilitytoGeometryInthisexercise,youlearnhowtointroducevariabilityintoyourgeometrythroughtheprocess

ofapplying

and

adjusting

parameters.

Figure3:Usingthesameglobaloperations,butwithdifferingvalues,atalocalscaletodetailthebridgerailings

Oncethebasegeometryiscreated,themodelingprocessbecomeslargelybaseduponthe

implementationof

parametric

variability

and

how

those

parameters

can

affect

the

form,

detail,

andpositioningofthegeometry.Wewillmakeadditionalelementsusingsomeofthetools

fromthepreviousexercise,butwewillmodifythecontrolparametersinordertosatisfy

differentmodelingrequirements.Forexample,wecreatedthebaseofthebridgebyfirst

extrudingandthenoffsettingtheoriginalspline.Tocreatethebridgerailings,weagainextrude

andoffsetthebasespline,thistimeusingsmallernumericalvaluesforthecontrolparameters.

Thesameoperationisused,buttheresultantgeometryvariesinbothdimensionandscale,

basedonthecontrolparametersthatcorrespondtodifferentdesigncriteria.


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Exercise4:InstancingParametricModificationsInthisexercise,youlearnhowtocopygeometricmodificationsthroughtheprocessof

instancingto

create

an

associative

parametric

system.

Figure4:Instancingbridgeparametersontoitstrusssothatbothgeometriescreateacomplexassociativesystem.

Creatinganinstanceisyetanotherformofcopying.Inthisexercise,wecreateinstancesof

parametersthat

we

have

already

applied

to

existing

geometry,

and

we

apply

them

to

additional

geometricelements.Bygeneratinginstancesofparametersalreadyinuseandapplyingthemto

newelementswithinthemodel,wewillparametricallylinkbothsetsofgeometrytoone

anothersothatmodificationstoeitheroneaffecttheother.Thislayeringofparameterscreates

associationsbetweendisparategeometricelementsandcanbeusedtocreatecomplexsystems

relativelyquickly.Inthislesson,wehavechosentoinstancetheparametersofthebridgeand

therailing,sothatthemovementofoneaffectstheotherinaconsistentmanner.

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