Obj Format

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B1.ObjectFiles(.obj)

ObjectfilesdefinethegeometryandotherpropertiesforobjectsinWavefront'sAdvancedVisualizer.ObjectfilescanalsobeusedtotransfergeometricdatabackandforthbetweentheAdvancedVisualizerandotherapplications.

ObjectfilescanbeinASCIIformat(.obj)orbinaryformat(.mod).ThisappendixdescribestheASCIIformatforobjectfiles.Thesefilesmusthavetheextension.obj.

Inthisrelease,the.objfileformatsupportsbothpolygonalobjectsandfree-formobjects.Polygonalgeometryusespoints,lines,andfacestodefineobjectswhilefree-formgeometryusescurvesandsurfaces.

Aboutthissection

The.objappendixisforthosewhowanttousethe.objformattotranslategeometricdatafromothersoftwareapplicationstoWavefrontproducts.ItalsoprovidesinformationforAdvancedVisualizeruserswhowantdetailedinformationontheWavefront.objfileformat.

Ifyouarea2.11userandwanttounderstandthesignificanceofthe3.0releaseandhowitaffectsyourexistingfiles,youmaybe

especiallyinterestedinthesectioncalled"Supersededstatements"attheendoftheappendix.Thesection,"Patchesandfree-formsurfaces,"givesexamplesofhow2.11patcheslookin3.0.

Howthissectionisorganized

Mostofthisappendixdescribesthedifferentpartsofan.objfileandhowthosepartsarearrangedinthefile.Thethreesectionsattheendoftheappendixprovidebackgroundinformationonthe3.0releaseofthe.objformat.

The.objappendixincludesthefollowingsections:

oFilestructure

oGeneralstatement

oVertexdata

oSpecifyingfree-formcurves/surfaces

oFree-formcurve/surfaceattributes

oElements

oFree-formcurve/surfacebodystatements

oConnectivitybetweenfree-formsurfaces

oGrouping

oDisplay/renderattributes

oComments

oMathematicsforfree-formcurves/surfaces


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oSupersededstatements

oPatchesandfree-formsurfaces

---------------

Thecurveandsurfaceextensionstothe.objfileformatweredevelopedinconjunctionwithmentalimagesGmbH&Co.KG,Berlin,Germany,aspartofajointdevelopmentprojecttoincorporatefree-formsurfacesintoWavefront'sAdvancedVisualizer.

Filestructure

Thefollowingtypesofdatamaybeincludedinan.objfile.Inthislist,thekeyword(inparentheses)followsthedatatype.

Vertexdata

ogeometricvertices(v)

otexturevertices(vt)

overtexnormals(vn)

oparameterspacevertices(vp)Free-formcurve/surfaceattributes

orationalornon-rationalformsofcurveorsurfacetype:basismatrix,Bezier,B-spline,Cardinal,Taylor(cstype)

odegree(deg)

obasismatrix(bmat)

ostepsize(step)

Elements

opoint(p)

oline(l)

oface(f)

ocurve(curv)

o2Dcurve(curv2)

osurface(surf)

Free-formcurve/surfacebodystatements

oparametervalues(parm)

ooutertrimmingloop(trim)

oinnertrimmingloop(hole)

ospecialcurve(scrv)


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ospecialpoint(sp)

oendstatement(end)

Connectivitybetweenfree-formsurfaces

oconnect(con)

Grouping

ogroupname(g)

osmoothinggroup(s)

omerginggroup(mg)

oobjectname(o)

Display/renderattributes

obevelinterpolation(bevel)

ocolorinterpolation(c_interp)

odissolveinterpolation(d_interp)

olevelofdetail(lod)

omaterialname(usemtl)

omateriallibrary(mtllib)

oshadowcasting(shadow_obj)

oraytracing(trace_obj)

ocurveapproximationtechnique(ctech)

osurfaceapproximationtechnique(stech)

Thefollowingdiagramshowshowthesepartsfittogetherinatypical.objfile.

FigureB1-1.Typical.objfilestructure

Generalstatement

callfilename.extarg1arg2...

Readsthecontentsofthespecified.objor.modfileatthislocation.Thecallstatementcanbeinsertedinto.objfilesusingatexteditor.

filename.extisthenameofthe.objor.modfiletoberead.Youmustincludetheextensionwiththefilename.

arg1arg2...specifiesaseriesofoptionalintegerarguments


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thatarepassedtothecalledfile.Thereisnolimittothenumberofnestedcallsthatcanbemade.

ArgumentspassedtothecalledfilearesubstitutedinthesamewayasinUNIXscripts;forexample,$1inthecalledfileisreplacedbyarg1,$2inthecalledfileisreplacedbyarg2,andsoon.

Iftheframenumberisneededinthecalledfileforvariablesubstitution,"$1"mustbeusedasthefirstargumentinthecallstatement.Forexample:

callfilename.obj$1

Thenthestatementinthecalledfile,

scmpfilename.pv$1

willworkasexpected.Formoreinformationonthescmpstatement,seeappendixC,VariableSubstitutionformoreinformation.

Anothermethodtodothesamethingis:

scmpfilename.pv$1

callfilename.obj

Usingthismethod,thescmpstatementprovidesthe.pvfileforallsubsequentlycalled.objor.modfiles.

cshcommand

csh-command

ExecutestherequestedUNIXcommand.IftheUNIXcommandreturnsanerror,theparserflagsanerrorduringparsing.

Ifadash(-)precedestheUNIXcommand,theerrorisignored.

commandistheUNIXcommand.

Vertexdata

Vertexdataprovidescoordinatesfor:

ogeometricvertices

otexturevertices

overtexnormals

Forfree-formobjects,thevertexdataalsoprovides:

oparameterspacevertices

Thevertexdataisrepresentedbyfourvertexlists;oneforeachtypeofvertexcoordinate.Aright-handcoordinatesystemisusedtospecifythecoordinatelocations.

Thefollowingsampleisaportionofan.objfilethatcontainsthefourtypesofvertexinformation.


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v-5.0000005.0000000.000000v-5.000000-5.0000000.000000v5.000000-5.0000000.000000v5.0000005.0000000.000000vt-5.0000005.0000000.000000vt-5.000000-5.0000000.000000vt5.000000-5.0000000.000000vt5.0000005.0000000.000000vn0.0000000.0000001.000000vn0.0000000.0000001.000000vn0.0000000.0000001.000000vn0.0000000.0000001.000000vp0.2100003.590000vp0.0000000.000000vp1.0000000.000000vp0.5000000.500000

WhenverticesareloadedintotheAdvancedVisualizer,theyaresequentiallynumbered,startingwith1.Thesereferencenumbersareusedinelementstatements.

Syntax

Thefollowingsyntaxstatementsarelistedinorderofcomplexity.

vxyzw

Polygonalandfree-formgeometrystatement.

Specifiesageometricvertexanditsxyzcoordinates.Rationalcurvesandsurfacesrequireafourthhomogeneouscoordinate,alsocalledtheweight.

xyzarethex,y,andzcoordinatesforthevertex.Theseare

floatingpointnumbersthatdefinethepositionofthevertexinthreedimensions.

wistheweightrequiredforrationalcurvesandsurfaces.Itisnotrequiredfornon-rationalcurvesandsurfaces.Ifyoudonotspecifyavalueforw,thedefaultis1.0.

NOTE:Apositiveweightvalueisrecommended.Usingzeroornegativevaluesmayresultinanundefinedpointinacurveorsurface.

vpuvw

Free-formgeometrystatement.

Specifiesapointintheparameterspaceofacurveorsurface.

Theusagedetermineshowmanycoordinatesarerequired.Specialpointsforcurvesrequirea1Dcontrolpoint(uonly)intheparameterspaceofthecurve.Specialpointsforsurfacesrequirea2Dpoint(uandv)intheparameterspaceofthesurface.Controlpointsfornon-rationaltrimmingcurvesrequireuandvcoordinates.Controlpointsforrationaltrimmingcurvesrequireu,


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v,andw(weight)coordinates.

uisthepointintheparameterspaceofacurveorthefirstcoordinateintheparameterspaceofasurface.

visthesecondcoordinateintheparameterspaceofasurface.

wistheweightrequiredforrationaltrimmingcurves.Ifyoudonotspecifyavalueforw,itdefaultsto1.0.

NOTE:Foradditionalinformationonparametervertices,seethecurv2andspstatements

vnijk


Specifiesanormalvectorwithcomponentsi,j,andk.

Vertexnormalsaffectthesmooth-shadingandrenderingofgeometry.Forpolygons,vertexnormalsareusedinplaceoftheactualfacetnormals.Forsurfaces,vertexnormalsareinterpolatedovertheentiresurfaceandreplacetheactualanalyticsurfacenormal.

Whenvertexnormalsarepresent,theysupersedesmoothinggroups.

ijkarethei,j,andkcoordinatesforthevertexnormal.Theyarefloatingpointnumbers.

vtuvw

Vertexstatementforbothpolygonalandfree-formgeometry.

Specifiesatexturevertexanditscoordinates.A1Dtexturerequiresonlyutexturecoordinates,a2Dtexturerequiresbothuandvtexturecoordinates,anda3Dtexturerequiresallthreecoordinates.

uisthevalueforthehorizontaldirectionofthetexture.

visanoptionalargument.

visthevaluefortheverticaldirectionofthetexture.Thedefaultis0.

wisanoptionalargument.

wisavalueforthedepthofthetexture.Thedefaultis0.

Specifyingfree-formcurves/surfaces

Therearethreestepsinvolvedinspecifyingafree-formcurveorsurfaceelement.

oSpecifythetypeofcurveorsurface(basismatrix,Bezier,B-spline,Cardinal,orTaylor)usingfree-formcurve/surfaceattributes.

oDescribethecurveorsurfacewithelementstatements.


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oSupplyadditionalinformation,usingfree-formcurve/surfacebodystatements

Thenextthreesectionsofthisappendixprovidedetailedinformationoneachofthesesteps.

Datarequirementsforcurvesandsurfaces

Allcurvesandsurfacesrequireacertainsetofdata.Thisconsistsofthefollowing:

Free-formcurve/surfaceattributes

oAllcurvesandsurfacesrequiretypedata,whichisgivenwiththecstypestatement.

oAllcurvesandsurfacesrequiredegreedata,whichisgivenwiththedegstatement.

oBasismatrixcurvesorsurfacesrequireabmatstatement.

oBasismatrixcurvesorsurfacesalsorequireastepsize,whichisgivenwiththestepstatement.

Elements

oAllcurvesandsurfacesrequirecontrolpoints,whicharereferencedinthecurv,curv2,orsurfstatements.

o3Dcurvesandsurfacesrequireaparameterrange,whichisgiveninthecurvandsurfstatements,respectively.


oAllcurvesandsurfacesrequireasetofglobalparametersoraknotvector,bothofwhicharegivenwiththeparmstatement.

oAllcurvesandsurfacesbodystatementsrequireanexplicitendstatement.

Errorchecks

Theabovesetofdatastartsoutemptywithnodefaultvalueswhenreadingofan.objfilebegins.Whilethefileisbeingread,statementsareencountered,informationisaccumulated,andsomeerrorsmaybereported.

Whentheendstatementisencountered,thefollowingerrorchecks,whichinvolveconsistencybetweenvariousstatements,areperformed:

oAllrequiredinformationispresent.

oThenumberofcontrolpoints,numberofparametervalues(knots),anddegreeareconsistentwiththecurveorsurfacetype.Ifthetypeisbmatrix,thestepsizeisalsoconsistent.(Formoreinformation,refertotheparametervectorequationsinthesection,"Mathematicsoffree-formcurves/surfaces"attheendofappendixB1.)

oIfthetypeisbmatrixandthedegreeisn,thesizeofthe


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basismatrixis(n+1)x(n+1).

Notethatanyinformationgivenbythestate-settingstatementsremainsineffectfromonecurveorsurfacetothenext.Informationgivenwithinacurveorsurfacebodyisonlyeffectiveforthecurveorsurfaceitisgivenwith.

Free-formcurve/surfaceattributes

Fivetypesoffree-formgeometryareavailableinthe.objfileformat:

oBezier

obasismatrix

oB-spline

oCardinal

oTaylor

Youcanapplythesetypesonlytocurvesandsurfaces.Eachofthesefivetypescanberationalornon-rational.

Inadditiontospecifyingthetype,youmustdefinethedegreeforthecurveorsurface.Forbasismatrixcurveandsurfaceelements,youmustalsospecifythebasismatrixandstepsize.

Allfree-formcurveandsurfaceattributestatementsarestate-setting.Thismeansthatonceanattributestatementisset,itappliestoallelementsthatfollowuntilitisresettoadifferentvalue.

Syntax

Thefollowingsyntaxstatementsarelistedinorderofuse.

cstyperattype


Specifiesthetypeofcurveorsurfaceandindicatesarationalornon-rationalform.

ratisanoptionalargument.

ratspecifiesarationalformforthecurveorsurfacetype.Ifratisnotincluded,thecurveorsurfaceisnon-rational

typespecifiesthecurveorsurfacetype.Allowedtypesare:

bmatrix basismatrix

bezier Bezier

bspline B-spline

cardinalCardinal


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taylor Taylor

Thereisnodefault.Avaluemustbesupplied.

degdegudegv


Setsthepolynomialdegreeforcurvesandsurfaces.

deguisthedegreeintheudirection.Itisrequiredforbothcurvesandsurfaces.

degvisthedegreeinthevdirection.Itisrequiredonlyforsurfaces.ForBezier,B-spline,Taylor,andbasismatrix,thereisnodefault;avaluemustbesupplied.ForCardinal,thedegreeisalways3.IfsomeothervalueisgivenforCardinal,itwillbeignored.

bmatumatrix

bmatvmatrix


Setsthebasismatricesusedforbasismatrixcurvesandsurfaces.Theuandvvaluesmustbespecifiedinseparatebmatstatements.

NOTE:Thedegstatementmustbegivenbeforethebmatstatementsandthesizeofthematrixmustbeappropriateforthedegree.

uspecifiesthatthebasismatrixisappliedintheudirection.

vspecifiesthatthebasismatrixisappliedinthevdirection.

matrixliststhecontentsofthebasismatrixwithcolumnsubscript

jvaryingthefastest.Ifnisthedegreeinthegivenuorvdirection,thematrix(i,j)shouldbeofsize(n+1)x(n+1).

Thereisnodefault.Avaluemustbesupplied.

NOTE:Thearrangementofthematrixisdifferentfromthatcommonlyfoundinotherreferences.Formoreinformation,seetheexamplesattheendofthissectionandalsothesection,"Mathematicsforfree-formcurvesandsurfaces."

stepstepustepv


Setsthestepsizeforcurvesandsurfacesthatuseabasismatrix.

stepuisthestepsizeintheudirection.Itisrequiredforbothcurvesandsurfacesthatuseabasismatrix.

stepvisthestepsizeinthevdirection.Itisrequiredonlyforsurfacesthatuseabasismatrix.Thereisnodefault.Avaluemustbesupplied.


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Whenacurveorsurfaceisbeingevaluatedandatransitionfromonesegmentorpatchtothenextoccurs,thesetofcontrolpointsusedisincrementedbythestepsize.Theappropriatestepsizedependsontherepresentationtype,whichisexpressedthroughthebasismatrix,andonthedegree.

Thatis,supposewearegivenacurvewithkcontrolpoints:{v,...v}1k

Ifthecurveisofdegreen,thenn+1controlpointsareneededforeachpolynomialsegment.Ifthestepsizeisgivenass,thentheithpolynomialsegment,wherei=0isthefirstsegment,willusethecontrolpoints:

{v,...,v}is+1is+n+1

Forexample,forBeziercurves,s=n.

Forsurfaces,theabovedescriptionappliesindependentlytoeachparametricdirection.

Whenyoucreateafilewhichusesthebasismatrixtype,besureto

specifyastepsizeappropriateforthecurrentcurveorsurfacerepresentation.

Examples

1.CubicBeziersurfacemadewithabasismatrix

TocreateacubicBeziersurface:

cstypebmatrixdeg33step33bmatu1-33-1\

03-63\003-3\0001

bmatv1-33-1\03-63\003-3\0001

2.Hermitecurvemadewithabasismatrix

TocreateaHermitecurve:

cstypebmatrix

deg3step2bmatu10-32003-2\

01-2100-11

3.BezierinudirectionwithB-splineinvdirection;madewithabasismatrix

TocreateasurfacewithacubicBezierintheudirectionandcubicuniformB-splineinthevdirection:


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cstypebmatrixdeg33step31bmatu1-33-1\

03-63\003-3\0001

bmatv0.16666-0.500000.50000-0.16666\0.666660.00000-1.000000.50000\0.166660.500000.50000-0.50000\0.000000.000000.000000.16666

Elements

Forpolygonalgeometry,theelementtypesavailableinthe.objfileare:

opoints

olines

ofaces

Forfree-formgeometry,theelementtypesavailableinthe.objfileare:

ocurve

o2Dcurveonasurface

osurface

Allelementscanbefreelyintermixedinthefile.

Referencingvertexdata

Forallelements,referencenumbersareusedtoidentifygeometricvertices,texturevertices,vertexnormals,andparameterspacevertices.

Eachofthesetypesofverticesisnumberedseparately,startingwith1.Thismeansthatthefirstgeometricvertexinthefileis1,thesecondis2,andsoon.Thefirsttexturevertexinthefileis1,thesecondis2,andsoon.Thenumberingcontinuessequentiallythroughouttheentirefile.Frequently,fileshavemultiplelistsofvertexdata.Thisnumberingsequencecontinuesevenwhenvertexdataisseparatedbyotherdata.

Inadditiontocountingverticesdownfromthetopofthefirstlistinthefile,youcanalsocountverticesbackupthelistfromanelement'spositioninthefile.Whenyoucountupthelistfromanelement,thereferencenumbersarenegative.Areferencenumberof-1indicatestheverteximmediatelyabovetheelement.Areferencenumberof-2indicatestworeferencesaboveandsoon.

Referencinggroupsofvertices


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Someelements,suchasfacesandsurfaces,mayhaveatripletofnumbersthatreferencevertexdata.Thesenumbersarethereferencenumbersforageometricvertex,atexturevertex,andavertexnormal.

Eachtripletofnumbersspecifiesageometricvertex,texturevertex,andvertexnormal.Thereferencenumbersmustbeinorderandmustseparatedbyslashes(/).

oThefirstreferencenumberisthegeometricvertex.

oThesecondreferencenumberisthetexturevertex.Itfollowsthefirstslash.

oThethirdreferencenumberisthevertexnormal.Itfollowsthesecondslash.

Thereisnospacebetweennumbersandtheslashes.Theremaybemorethanoneseriesofgeometricvertex/texturevertex/vertexnormalnumbersonaline.

Thefollowingisaportionofasamplefileforafour-sidedfaceelement:

f1/1/12/2/23/3/34/4/4

Usingv,vt,andvntorepresentgeometricvertices,texturevertices,andvertexnormals,thestatementwouldread:

fv/vt/vnv/vt/vnv/vt/vnv/vt/vn

Ifthereareonlyverticesandvertexnormalsforafaceelement(notexturevertices),youwouldentertwoslashes(//).Forexample,tospecifyonlythevertexandvertexnormalreferencenumbers,youwouldenter:

f1//12//23//34//4

Whenyouareusingaseriesoftriplets,youmustbeconsistentinthewayyoureferencethevertexdata.Forexample,itisillegaltogivevertexnormalsforsomevertices,butnotall.

Thefollowingisanexampleofanillegalstatement.

f1/1/12/2/23//34//4

Syntax

Thefollowingsyntaxstatementsarelistedinorderofcomplexityofgeometry.

pv1v2v3...

Polygonalgeometrystatement.

Specifiesapointelementanditsvertex.Youcanspecifymultiplepointswiththisstatement.Althoughpointscannotbeshadedorrendered,theyareusedbyotherAdvancedVisualizerprograms.

visthevertexreferencenumberforapointelement.Eachpointelementrequiresonevertex.Positivevaluesindicateabsolute


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vertexnumbers.Negativevaluesindicaterelativevertexnumbers.

lv1/vt1v2/vt2v3/vt3...


Specifiesalineanditsvertexreferencenumbers.Youcanoptionallyincludethetexturevertexreferencenumbers.Althoughlinescannotbeshadedorrendered,theyareusedbyotherAdvancedVisualizerprograms.

Thereferencenumbersfortheverticesandtextureverticesmustbeseparatedbyaslash(/).Thereisnospacebetweenthenumberandtheslash.

visareferencenumberforavertexontheline.Aminimumoftwovertexnumbersarerequired.Thereisnolimitonthemaximum.Positivevaluesindicateabsolutevertexnumbers.Negativevaluesindicaterelativevertexnumbers.

vtisanoptionalargument.

vtisthereferencenumberforatexturevertexinthelineelement.Itmustalwaysfollowthefirstslash.

fv1/vt1/vn1v2/vt2/vn2v3/vt3/vn3...


Specifiesafaceelementanditsvertexreferencenumber.Youcanoptionallyincludethetexturevertexandvertexnormalreferencenumbers.

Thereferencenumbersforthevertices,texturevertices,andvertexnormalsmustbeseparatedbyslashes(/).Thereisnospacebetweenthenumberandtheslash.

visthereferencenumberforavertexinthefaceelement.Aminimumofthreeverticesarerequired.


vtisthereferencenumberforatexturevertexinthefaceelement.Italwaysfollowsthefirstslash.

vnisanoptionalargument.

vnisthereferencenumberforavertexnormalinthefaceelement.Itmustalwaysfollowthesecondslash.

Faceelementsusesurfacenormalstoindicatetheirorientation.Ifverticesareorderedcounterclockwisearoundtheface,boththefaceandthenormalwillpointtowardtheviewer.Ifthevertexorderingisclockwise,bothwillpointawayfromtheviewer.Ifvertexnormalsareassigned,theyshouldpointinthegeneraldirectionofthesurfacenormal,otherwiseunpredictableresultsmayoccur.

Ifafacehasatexturemapassignedtoitandnotextureverticesareassignedinthefstatement,thetexturemapisignoredwhen


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theelementisrendered.

NOTE:Anyreferencestofo(faceoutline)arenolongervalidasofversion2.11.Youcanusef(face)togetthesameresults.Referencestofoinexisting.objfileswillstillberead,however,theywillbewrittenoutasfwhenthefileissaved.

curvu0u1v1v2...

Elementstatementforfree-formgeometry.

Specifiesacurve,itsparameterrange,anditscontrolvertices.Althoughcurvescannotbeshadedorrendered,theyareusedbyotherAdvancedVisualizerprograms.

u0isthestartingparametervalueforthecurve.Thisisafloatingpointnumber.

u1istheendingparametervalueforthecurve.Thisisafloatingpointnumber.

visthevertexreferencenumberforacontrolpoint.Youcanspecifymultiplecontrolpoints.Aminimumoftwocontrolpointsarerequiredforacurve.

Foranon-rationalcurve,thecontrolpointsmustbe3D.Forarationalcurve,thecontrolpointsare3Dor4D.Thefourthcoordinate(weight)defaultsto1.0ifomitted.

curv2vp1vp2vp3...


Specifiesa2Dcurveonasurfaceanditscontrolpoints.A2Dcurveisusedasanouterorinnertrimmingcurve,asaspecialcurve,orforconnectivity.

vpistheparametervertexreferencenumberforthecontrolpoint.Youcanspecifymultiplecontrolpoints.Aminimumoftwocontrolpointsisrequiredfora2Dcurve.

Thecontrolpointsareparameterverticesbecausethecurvemustlieintheparameterspaceofsomesurface.Foranon-rationalcurve,thecontrolverticescanbe2D.Forarationalcurve,thecontrolverticescanbe2Dor3D.Thethirdcoordinate(weight)defaultsto1.0ifomitted.

surfs0s1t0t1v1/vt1/vn1v2/vt2/vn2...

Elementstatementforfree-formgeometry.

Specifiesasurface,itsparameterrange,anditscontrolvertices.Thesurfaceisevaluatedwithintheglobalparameterrangefroms0tos1intheudirectionandt0tot1inthevdirection.

s0isthestartingparametervalueforthesurfaceintheudirection.

s1istheendingparametervalueforthesurfaceintheudirection.


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t0isthestartingparametervalueforthesurfaceinthevdirection.

t1istheendingparametervalueforthesurfaceinthevdirection.

visthereferencenumberforacontrolvertexinthesurface.


vtisthereferencenumberforatexturevertexinthesurface.Itmustalwaysfollowthefirstslash.

vnisanoptionalargument.

vnisthereferencenumberforavertexnormalinthesurface.Itmustalwaysfollowthesecondslash.

Foranon-rationalsurface,thecontrolverticesare3D.Forarationalsurfacethecontrolverticescanbe3Dor4D.Thefourthcoordinate(weight)defaultsto1.0ifommitted.

NOTE:Formoreinformationontheorderingofcontrolpointsfor

survaces,refertothesectiononsurfacesandcontrolpointsin"mathematicsoffree-formcurves/surfaces"attheendofthisappendix.

Examples

Theseareexamplesforpolygonalgeometry.

Forexamplesusingfree-formgeometry,seetheexamplesattheendofthenextsection,"Free-formcurve/surfacebodystatements."

1. Square

Thisexampleshowsasquarethatmeasurestwounitsoneachsideandfacesinthepositivedirection(towardthecamera).Notethattheorderingoftheverticesiscounterclockwise.Thisorderingdeterminesthatthesquareisfacingforward.

v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000v2.0000002.0000000.000000f1234

2.Cube

Thisisacubethatmeasurestwounitsoneachside.Eachvertexissharedbythreedifferentfaces.

v0.0000002.0000002.000000v0.0000000.0000002.000000v2.0000000.0000002.000000v2.0000002.0000002.000000


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v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000v2.0000002.0000000.000000f1234f8765f4378f5148f5621f2673

3.Cubewithnegativereferencenumbers

Thisisacubewithnegativevertexreferencenumbers.Eachelementreferencestheverticesstoredimmediatelyaboveitinthefile.Notethatverticesarenotshared.

v0.0000002.0000002.000000v0.0000000.0000002.000000v2.0000000.0000002.000000v2.0000002.0000002.000000f-4-3-2-1

v2.0000002.0000000.000000

v2.0000000.0000000.000000v0.0000000.0000000.000000v0.0000002.0000000.000000f-4-3-2-1

v2.0000002.0000002.000000v2.0000000.0000002.000000v2.0000000.0000000.000000v2.0000002.0000000.000000f-4-3-2-1

v0.0000002.0000000.000000v0.0000002.0000002.000000

v2.0000002.0000002.000000v2.0000002.0000000.000000f-4-3-2-1

v0.0000002.0000000.000000v0.0000000.0000000.000000v0.0000000.0000002.000000v0.0000002.0000002.000000f-4-3-2-1

v0.0000000.0000002.000000v0.0000000.0000000.000000v2.0000000.0000000.000000

v2.0000000.0000002.000000f-4-3-2-1


Youcanspecifyadditionalinformationforfree-formcurveandsurfaceelementsusingaseriesofstatementscalledbodystatements.Theseriesisconcludedbyanendstatement.


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Bodystatementsarevalidonlywhentheyappearbetweenthefree-formelementstatement(curv,curv2,surf)andtheendstatement.Iftheyareanywhereelseinthe.objfile,theydonothaveanyeffect.

Youcanusebodystatementstospecifythefollowingvalues:

oparameter

oknotvector

otrimmingloop

ohole

ospecialcurve

ospecialpoint

Youcannotuseanyotherstatementsbetweenthefree-formcurveorsurfacestatementandtheendstatement.Usinganyotheroftypeofstatementmaycauseunpredictableresults.

Thisportionofasamplefileshowstheknotvectorvaluesfora

rationalB-splinesurfacewithatrimmingloop.Noticetheendstatementtoconcludethebodystatements.

cstyperatbsplinedeg22surf-1.02.5-2.02.0-9-8-7-6-5-4-3-2-1parmu-1.00-1.00-1.002.502.502.50parmv-2.00-2.00-2.00-2.00-2.00-2.00trim0.02.01end

Parametervaluesandknotvectors

Allcurveandsurfaceelementsrequireasetofparametervalues.

Forpolynomialcurvesandsurfaces,thisspecifiesglobalparametervalues.ForB-splinecurvesandsurfaces,thisspecifiestheknotvectors.

Forsurfaces,theparametervaluesmustbespecifiedforboththeuandvdirections.Forcurves,theparametervaluesmustbespecifiedforonlytheudirection.

Ifmultipleparametervaluestatementsforthesameparametricdirectionareusedinsideasinglecurveorsurfacebody,thelaststatementisused.

Trimmingloopsandholes

Thetrimmingloopstatementbuildsasingleoutertrimmingloopasasequenceofcurveswhichlieonagivensurface.

Theholestatementbuildsasingleinnertrimmingloopasasequenceofcurveswhichlieonagivensurface.Theinnerloopcreatesahole.

Thecurvesarereferencedbynumberinthesamewayverticesare


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referencedbyfaceelements.

Theindividualcurvesmustlieend-to-endtoformaclosedloopwhichdoesnotintersectitselfandwhichlieswithintheparameterrangespecifiedforthesurface.Theloopasawholemaybeorientedineitherdirection(clockwiseorcounterclockwise).

Tocutoneormoreholesinaregion,useatrimstatementfollowedbyoneormoreholestatements.Tointroduceanothertrimmedregioninthesamesurface,useanothertrimstatementfollowedbyoneormoreholestatements.Theorderingthatassociatesholesandtheregionstheycutisimportantandmustbemaintained.

Ifthefirsttrimstatementinthesequenceisomitted,theenclosingoutertrimmingloopistakentobetheparameterrangeofthesurface.Ifnotrimorholestatementsarespecified,thenthesurfaceistrimmedatitsparameterrange.

Thisportionofasamplefileshowsanon-rationalBeziersurfacewithtworegions,eachwithasinglehole:

cstypebezierdeg11surf0.02.00.02.01234

parmu0.002.00parmv0.002.00trim0.04.01hole0.04.02trim0.04.03hole0.04.04end

Specialcurve

Aspecialcurvestatementbuildsasinglespecialcurveasasequenceofcurveswhichlieonagivensurface.

Thecurvesarereferencedbynumberinthesamewayverticesarereferencedbyfaceelements.

Aspecialcurveisguaranteedtobeincludedinanytriangulationofthesurface.Thismeansthatthelineformedbyapproximatingthespecialcurvewithasequenceofstraightlinesegmentswillactuallyappearasasequenceoftriangleedgesinthefinaltriangulation.

Specialpoint

Aspecialpointstatementspecifiesthatspecialgeometricpointsaretobeassociatedwithacurveorsurface.Forspacecurvesandtrimmingcurves,theparameterverticesmustbe1D.Forsurfaces,theparameter

verticesmustbe2D.

Thesespecialpointswillbeincludedinanylinearapproximationofthecurveorsurface.

Forspacecurves,thismeansthatthepointcorrespondingtothegivencurveparameterisincludedasoneoftheverticesinanapproximationconsistingofasequenceoflinesegments.

Forsurfaces,thismeansthatthepointcorrespondingtothegiven


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holeu0u1curv2du0u1curv2d...

Bodystatementforfree-formgeometry.

Specifiesasequenceofcurvestobuildasingleinnertrimmingloop(hole).

u0isthestartingparametervalueforthetrimmingcurvecurv2d.

u1istheendingparametervalueforthetrimmingcurvecurv2d.

curv2distheindexofthetrimmingcurvelyingintheparameterspaceofthesurface.Thiscurvemusthavebeenpreviouslydefinedwiththecurv2statement.

scrvu0u1curv2du0u1curv2d...


Specifiesasequenceofcurveswhichlieonthegivensurfacetobuildasinglespecialcurve.

u0isthestartingparametervalueforthespecialcurvecurv2d.

u1istheendingparametervalueforthespecialcurvecurv2d.

curv2distheindexofthespecialcurvelyingintheparameterspaceofthesurface.Thiscurvemusthavebeenpreviouslydefinedwiththecurv2statement.

spvp1vp...


Specifiesspecialgeometricpointstobeassociatedwithacurveorsurface.Forspacecurvesandtrimmingcurves,theparameter

verticesmustbe1D.Forsurfaces,theparameterverticesmustbe2D.

vpisthereferencenumberfortheparametervertexofaspecialpointtobeassociatedwiththeparameterspacepointofthecurveorsurface.

end


Specifiestheendofacurveorsurfacebodybegunbyacurv,curv2,orsurfstatement.

Examples

1.Taylorcurve

Forcreatingasingle-segmentTaylorpolynomialcurveoftheform:

234x=3.00+2.30t+7.98t+8.30t+6.34t


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234y=1.00-10.10t+5.40t-4.70t+2.03t

234z=-2.50+0.50t-7.00t+18.10t+0.08t

andevaluatedbetweentheglobalparameters0.5and1.6:

v3.0001.000-2.500v2.300-10.1000.500v7.9805.400-7.000v8.300-4.70018.100v6.3402.0300.080cstypetaylordeg4curv0.5001.60012345parmu0.0002.000end

2.Beziercurve

Thisexampleshowsanon-rationalBeziercurvewith13controlpoints.

v-2.3000001.9500000.000000v-2.2000000.7900000.000000v-2.340000-1.5100000.000000v-1.530000-1.4900000.000000v-0.720000-1.4700000.000000v-0.7800000.2300000.000000v0.0700000.2500000.000000v0.9200000.2700000.000000v0.800000-1.6100000.000000v1.620000-1.5900000.000000v2.440000-1.5700000.000000v2.6900000.6700000.000000v2.9000001.9800000.000000

#13vertices

cstypebezierctechcparm1.000000deg3curv0.0000004.00000012345678910\111213parmu0.0000001.0000002.0000003.000000\4.000000end#1element

3.B-splinesurface

ThisisanexampleofacubicB-splinesurface.

gbspatchv-5.000000-5.000000-7.808327v-5.000000-1.666667-7.808327v-5.0000001.666667-7.808327v-5.0000005.000000-7.808327


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v-1.666667-5.000000-7.808327v-1.666667-1.66666711.977780v-1.6666671.66666711.977780v-1.6666675.000000-7.808327v1.666667-5.000000-7.808327v1.666667-1.66666711.977780v1.6666671.66666711.977780v1.6666675.000000-7.808327v5.000000-5.000000-7.808327v5.000000-1.666667-7.808327v5.0000001.666667-7.808327v5.0000005.000000-7.808327#16vertices

cstypebsplinestechcurv0.510.000000deg338surf0.0000001.0000000.0000001.0000001314\1516910111256781234parmu-3.000000-2.000000-1.0000000.000000\1.0000002.0000003.0000004.000000parmv-3.000000-2.000000-1.0000000.000000\1.0000002.0000003.0000004.000000end

#1element

4.Cardinalsurface

ThisexampleshowsaCardinalsurface.

v-5.000000-5.0000000.000000v-5.000000-1.6666670.000000v-5.0000001.6666670.000000v-5.0000005.0000000.000000v-1.666667-5.0000000.000000v-1.666667-1.6666670.000000

v-1.6666671.6666670.000000v-1.6666675.0000000.000000v1.666667-5.0000000.000000v1.666667-1.6666670.000000v1.6666671.6666670.000000v1.6666675.0000000.000000v5.000000-5.0000000.000000v5.000000-1.6666670.000000v5.0000001.6666670.000000v5.0000005.0000000.000000#16vertices

cstypecardinal

stechcparma1.0000001.000000deg33surf0.0000001.0000000.0000001.0000001314\1516910111256781234parmu0.0000001.000000parmv0.0000001.000000end#1element


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5.RationalB-splinesurface

Thisexamplecreatesasecond-degree,rationalB-splinesurfaceusingopen,uniformknotvectors.Atexturemapisappliedtothesurface.

v-1.3-1.00.0v0.1-1.00.47.6v1.4-1.00.02.3v-1.40.00.2v0.10.00.90.5v1.30.00.41.5v-1.41.00.02.3v0.11.00.36.1v1.11.00.03.3vt0.00.0vt0.50.0vt1.00.0vt0.00.5vt0.50.5vt1.00.5vt0.01.0vt0.51.0vt1.01.0cstyperatbspline

deg22surf0.01.00.01.01/12/23/34/45/56/6\7/78/89/9parmu0.00.00.01.01.01.0parmv0.00.00.01.01.01.0end

6.TrimmedNURBsurface

ThisisacompleteexampleofafilecontainingatrimmedNURBsurfacewithnegativereferencenumbersforvertices.

#trimmingcurvevp-0.6751.8503.000vp0.9151.930vp2.4850.4702.000vp2.485-1.030vp1.605-1.89010.700vp-0.745-0.6540.500cstyperatbezierdeg3curv2-6-5-4-3-2-1-6parmu0.001.002.00end#surface

v-1.350-1.0300.000v0.130-1.0300.4327.600v1.480-1.0300.0002.300v-1.4600.0600.201v0.1200.0600.9150.500v1.3800.0600.4541.500v-1.4801.0300.0002.300v0.1201.0300.3946.100v1.1701.0300.0003.300cstyperatbspline


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deg22surf-1.02.5-2.02.0-9-8-7-6-5-4-3-2-1parmu-1.00-1.00-1.002.502.502.50parmv-2.00-2.00-2.00-2.00-2.00-2.00trim0.02.01end

7.Twotrimmingregionswithahole

ThisexampleshowsaBeziersurfacewithtwotrimmingregions,eachwithaholeinthem.

#outerloopoffirstregiondeg1cstypebeziervp0.1000.100vp0.9000.100vp0.9000.900vp0.1000.900curv212341parmu0.001.002.003.004.00end#holeinfirstregion

vp0.3000.300vp0.7000.300vp0.7000.700vp0.3000.700curv256785parmu0.001.002.003.004.00end#outerloopofsecondregionvp1.1001.100vp1.9001.100vp1.9001.900vp1.1001.900curv291011129

parmu0.001.002.003.004.00end#holeinsecondregionvp1.3001.300vp1.7001.300vp1.7001.700vp1.3001.700curv21314151613parmu0.001.002.003.004.00end#surfacev0.0000.0000.000v1.0000.0000.000

v0.0001.0000.000v1.0001.0000.000deg11cstypebeziersurf0.02.00.02.01234parmu0.002.00parmv0.002.00trim0.04.01hole0.04.02trim0.04.03


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hole0.04.04end

8.TrimmingwithaspecialcurveThisexampleissimilartothetrimmedNURBsurfaceexample(6),exceptthereisaspecialcurveonthesurface.Thisexampleusesnegativevertexnumbers.

#trimmingcurvevp-0.6751.8503.000vp0.9151.930vp2.4850.4702.000vp2.485-1.030vp1.605-1.89010.700vp-0.745-0.6540.500cstyperatbezierdeg3curv2-6-5-4-3-2-1-6parmu0.001.002.00end#specialcurvevp-0.1850.322vp0.2140.818

vp1.6520.207vp1.652-0.455curv2-4-3-2-1parmu2.0010.00end#surfacev-1.350-1.0300.000v0.130-1.0300.4327.600v1.480-1.0300.0002.300v-1.4600.0600.201v0.1200.0600.9150.500v1.3800.0600.4541.500v-1.4801.0300.0002.300

v0.1201.0300.3946.100v1.1701.0300.0003.300cstyperatbsplinedeg22surf-1.02.5-2.02.0-9-8-7-6-5-4-3-2-1parmu-1.00-1.00-1.002.502.502.50parmv-2.00-2.00-2.002.002.002.00trim0.02.01scrv4.29.72end

9.Trimmingwithspecialpoints

ThisexampleextendsthetrimmedNURBsurfaceexample(6)toincludespecialpointsonboththetrimmingcurveandsurface.Aspacecurvewithaspecialpointisalsoincluded.Thisexampleusesnegativevertexnumbers.

#specialpointandspacecurvedatavp0.500vp0.700vp1.100


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vp0.2000.950v0.3001.5000.100v0.0000.0000.000v1.0001.0000.000v2.0001.0000.000v3.0000.0000.000cstypebezierdeg3curv0.20.9-4-3-2-1sp1parmu0.001.00end#trimmingcurvevp-0.6751.8503.000vp0.9151.930vp2.4850.4702.000vp2.485-1.030vp1.605-1.89010.700vp-0.745-0.6540.500cstyperatbeziercurv2-6-5-4-3-2-1-6parmu0.001.002.00sp23end

#surfacev-1.350-1.0300.000v0.130-1.0300.4327.600v1.480-1.0300.0002.300v-1.4600.0600.201v0.1200.0600.9150.500v1.3800.0600.4541.500v-1.4801.0300.0002.300v0.1201.0300.3946.100v1.1701.0300.0003.300cstyperatbsplinedeg22surf-1.02.5-2.02.0-9-8-7-6-5-4-3-2-1

parmu-1.00-1.00-1.002.502.502.50parmv-2.00-2.00-2.002.002.002.00trim0.02.01sp4end

Connectivitybetweenfree-formsurfaces

Connectivityconnectstwosurfacesalongtheirtrimmingcurves.

Theconstatementspecifiesthefirstsurfacewithitstrimmingcurveandthesecondsurfacewithitstrimmingcurve.Thisinformationisusefulforedgemerging.Withoutthissurfaceandcurvedata,

connectivitymustbedeterminednumericallyatgreaterexpenseandwithreducedaccuracyusingthemgstatement.

Connectivitybetweensurfacesindifferentmerginggroupsisignored.Also,althoughconnectivitywhichcrossespointsofC1discontinuityintrimmingcurvesislegal,itisnotrecommended.Instead,usetwoconnectivitystatementswhichmeetatthepointofdiscontinuity.

Thetwocurvesandtheirstartingandendingparametersshouldallmaptothesamecurveandstartingandendingpointsinobjectspace.


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Syntax

consurf_1q0_1q1_1curv2d_1surf_2q0_2q1_2curv2d_2


Specifiesconnectivitybetweentwosurfaces.

surf_1istheindexofthefirstsurface.

q0_1isthestartingparameterforthecurvereferencedbycurv2d_1.

q1_1istheendingparameterforthecurvereferencedbycurv2d_1.

curv2d_1istheindexofacurveonthefirstsurface.Thiscurvemusthavebeenpreviouslydefinedwiththecurv2statement.

surf_2istheindexofthesecondsurface.

q0_2isthestartingparameterforthecurvereferencedbycurv2d_2.

q1_2istheendingparameterforthecurvereferencedbycurv2d_2.

curv2d_2istheindexofacurveonthesecondsurface.Thiscurvemusthavebeenpreviouslydefinedwiththecurv2statement.

Example

1.Connectivitybetweentwosurfaces

Thisexampleshowstheconnectivitybetweentwosurfaceswithtrimmingcurves.

cstypebezier

deg11

v000v100v010v110

vp00vp10vp11vp01

curv212341

parmu0.01.02.03.04.0end

surf0.01.00.01.01234parmu0.01.0parmv0.01.0trim0.04.01end

v100


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v200v110v210

surf0.01.00.01.05678parmu0.01.0parmv0.01.0trim0.04.01end

con12.02.0124.03.01

Grouping

Therearefourstatementsinthe.objfiletohelpyoumanipulategroupsofelements:

o GropunamestatementsareusedtoorganizecollectionsofelementsandsimplifydatamanipulationforoperationsinModel.

o Smoothinggroupstatementsletyouidentifyelementsoverwhichnormalsaretobeinterpolatedtogivethoseelementsasmooth,

non-facetedappearance.Thisisaquickwaytospecifyvertexnormals.

o Merginggroupstatementsareusedtoideneifyfree-formelementsthatshouldbeinspectedforadjacencydetection.Youcanalsousemerginggroupstoexcludesurfaceswhicharecloseenoughtobeconsideredadjacentbutshouldnotbemerged.

o Objectnamestatementsletyouassignanametoanentireobjectinasinglefile.

Allgroupingstatementsarestate-setting.Thismeansthatonceagroupstatementisset,itappliestoallelementsthatfollow

untilthenextgroupstatement.

Thisportionofasamplefileshowsasingleelementwhichbelongstothreegroups.Thesmoothinggroupisturnedoff.

gsquarethingallsofff1234

Thisexampleshowstwosurfacesinmerginggroup1withamergeresolutionof0.5.

mg1.5

surf0.01.012345678910111213141516surf0.01.017181920212223242526272829303132

Syntax

ggroup_name1group_name2...


Specifiesthegroupnamefortheelementsthatfollowit.Youcan


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havemultiplegroupnames.Iftherearemultiplegroupsononeline,thedatathatfollowsbelongtoallgroups.Groupinformationisoptional.

group_nameisthenameforthegroup.Letters,numbers,andcombinationsoflettersandnumbersareacceptedforgroupnames.Thedefaultgroupnameisdefault.

sgroup_number


Setsthesmoothinggroupfortheelementsthatfollowit.Ifyoudonotwanttouseasmoothinggroup,specifyofforavalueof0.

TodisplaywithsmoothshadinginModelandPreView,youmustcreatevertexnormalsafteryouhaveassignedthesmoothinggroups.YoucancreatevertexnormalswiththevnstatementorwiththeModelprogram.

TosmoothpolygonalgeometryforrenderingwithImage,itissufficienttoputelementsinsomesmoothinggroup.However,vertexnormalsoverridesmoothinginformationforImage.

group_numberisthesmoothinggroupnumber.Toturnoffsmoothinggroups,useavalueof0oroff.Polygonalelementsusegroupnumberstoputelementsindifferentsmoothinggroups.Forfree-formsurfaces,smoothinggroupsareeitherturnedonoroff;thereisnodifferencebetweenvaluesgreaterthan0.

mggroup_numberres


Setsthemerginggroupandmergeresolutionforthefree-formsurfacesthatfollowit.Ifyoudonotwanttouseamerginggroup,specifyofforavalueof0.

Adjacencydetectionisperformedonlywithingroups,neverbetweengroups.Connectivitybetweensurfacesindifferentmerginggroupsisnotallowed.Surfacesinthesamemerginggrouparemergedtogetheralongedgesthatarewithinthedistanceresapart.

NOTE:Adjacencydetectionisanexpensivenumericalcomparisonprocess.Itisbesttorestrictthisprocesstoassmalladomainaspossiblebyusingsmallmerginggroups.

group_numberisthemerginggroupnumber.Toturnoffadjacencydetection,useavalueof0oroff.

resisthemaximumdistancebetweentwosurfacesthatwillbemergedtogether.Theresolutionmustbeavaluegreaterthan0.Thisisarequiredargumentonlywhenusingmerginggroups.

oobject_name


Optionalstatement;itisnotprocessedbyanyWavefrontprograms.Itspecifiesauser-definedobjectnamefortheelementsdefined


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afterthisstatement.

object_nameistheuser-definedobjectname.Thereisnodefault.

Examples

1.Cubewithgroupnames

Thefollowingexampleisacubewitheachofitsfacesplacedinaseparategroup.Inaddition,allelementsbelongtothegroupcube.

v0.0000002.0000002.000000v0.0000000.0000002.000000v2.0000000.0000002.000000v2.0000002.0000002.000000v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000v2.0000002.0000000.000000#8vertices

gfrontcubef1234gbackcube

f8765grightcubef4378gtopcubef5148gleftcubef5621gbottomcubef2673#6elements

2.Twoadjoiningsquareswithasmoothinggroup

Thisexampleshowstwoadjoiningsquaresthatshareacommonedge.ThesquaresareplacedinasmoothinggrouptoensurethattheircommonedgewillbesmoothedwhenrenderedwithImage.

v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000v2.0000002.0000000.000000v4.0000000.000000-1.255298v4.0000002.000000-1.255298#6vertices

galls1f1234f4356#2elements

3.Twoadjoiningsquareswithvertexnormals

Thisexamplealsoshowstwosquaresthatshareacommonedge.Vertex


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normalshavebeenaddedtothecornersofeachsquaretoensurethattheircommonedgewillbesmoothedduringdisplayinModelandPreViewandwhenrenderedwithImage.

v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000v2.0000002.0000000.000000v4.0000000.000000-1.255298v4.0000002.000000-1.255298vn0.0000000.0000001.000000vn0.0000000.0000001.000000vn0.2765970.0000000.960986vn0.2765970.0000000.960986vn0.5316110.0000000.846988vn0.5316110.0000000.846988#6vertices

#6normals

galls1f1//12//23//34//4f4//43//35//56//6

#2elements

4.Merginggroup

ThisexampleshowstwoBeziersurfacesthatmeetatacommonedge.Theyhavebothbeenplacedinthesamemerginggrouptoensurecontinuityattheedgewheretheymeet.Thisprevents"cracks"fromappearingalongtheseambetweenthetwosurfacesduringrendering.Merginggroupswillbeignoredduringflat-shading,smooth-shading,andmaterialshadingofthesurface.

v-4.949854-5.0000000.000000

v-4.949854-1.6666670.000000v-4.9498541.6666670.000000v-4.9498545.0000000.000000v-1.616521-5.0000000.000000v-1.616521-1.6666670.000000v-1.6165211.6666670.000000v-1.6165215.0000000.000000v1.716813-5.0000000.000000v1.716813-1.6666670.000000v1.7168131.6666670.000000v1.7168135.0000000.000000v5.050146-5.0000000.000000v5.050146-1.6666670.000000

v5.0501461.6666670.000000v5.0501465.0000000.000000v-15.015566-4.9749910.000000v-15.015566-1.6416580.000000v-15.0155661.6916750.000000v-15.0155665.0250090.000000v-11.682233-4.9749910.000000v-11.682233-1.6416580.000000v-11.6822331.6916750.000000v-11.6822335.0250090.000000


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v-8.348900-4.9749910.000000v-8.348900-1.6416580.000000v-8.3489001.6916750.000000v-8.3489005.0250090.000000v-5.015566-4.9749910.000000v-5.015566-1.6416580.000000v-5.0155661.6916750.000000v-5.0155665.0250090.000000

mg10.500000

cstypebezierdeg33surf0.0000001.0000000.0000001.0000001314\1516910111256781234parmu0.0000001.000000parmv0.0000001.000000endsurf0.0000001.0000000.0000001.00000029303132252627282122\232417181920parmu0.0000001.000000parmv0.0000001.000000end

Display/renderattributes

DisplayandrenderattributesdescribehowanobjectlookswhendisplayedinModelandPreVieworwhenrenderedwithImage.

Someattributesapplytobothfree-formandpolygonalgeometry,suchasmaterialnameandlibrary,raytracing,andshadowcasting.Interpolationattributesapplyonlytopolygonalgeometry.Curveandsurfaceresolutionsareusedforonlyfree-formgeometry.

Thefollowingchartshowsthedisplayandrenderstatementsavailableforpolygonalandfree-formgeometry.

TableB1-1.Displayandrenderattributes

polygonalonly polygonalorfree-form free-formonly-------------- ---------------------- --------------bevel lod ctechc_interp usemtl stechd_interp mtllib

shadow_objtrace_obj

Alldisplayandrenderattributestatementsarestate-setting.Thismeansthatonceanattributestatementisset,itappliestoall

elementsthatfollowuntilitisresettoadifferentvalue.

Thefollowingsampleshowsrenderinganddisplaystatementsforafaceelement.:

s1usemtlblueusemapmarblef1234


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Syntax

Thefollowingsyntaxstatementsarelistedbythetypeofgeometry.Firstarestatementsforpolygonalgeometry.Secondarestatementsforbothfree-formandpolygonalgeometry.Thirdarestatementsforfree-formgeometryonly.

bevelon/off


Setsbevelinterpolationonoroff.Itworksonlywithbeveledobjects,thatis,objectswithsidesseparatedbybeveledfaces.

Bevelinterpolationusesnormalvectorinterpolationtogiveanillusionofroundnesstoaflatbevel.Itdoesnotaffectthesmoothingofnon-bevelledfaces.

Bevelinterpolationdoesnotalterthegeometryoftheoriginalobject.

onturnsonbevelinterpolation.

offturnsoffbevelinterpolation.Thedefaultisoff.

NOTE:Imagecannotrenderbevel-interpolatedelementsthathavevertexnormals.

c_interpon/off


Setscolorinterpolationonoroff.

Colorinterpolationcreatesablendacrossthesurfaceofapolygonbetweenthematerialsassignedtoitsvertices.Thiscreatesablendingofcolorsacrossafaceelement.

Tosupportcolorinterpolation,materialsmustbeassignedpervertex,notperelement.Theilluminationmodelsforallmaterialsofverticesattachedtothepolygonmustbethesame.Colorinterpolationappliestothevaluesforambient(Ka),diffuse(Kd),specular(Ks),andspecularhighlight(Ns)materialproperties.

onturnsoncolorinterpolation.

offturnsoffcolorinterpolation.Thedefaultisoff.

d_interpon/off


Setsdissolveinterpolationonoroff.

Dissolveinterpolationcreatesaninterpolationorblendacrossapolygonbetweenthedissolve(d)valuesofthematerialsassignedtoitsvertices.Thisfeatureisusedtocreateeffectsexhibitingvaryingdegreesofapparenttransparency,asinglassorclouds.

Tosupportdissolveinterpolation,materialsmustbeassignedper


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mtllibfilename1filename2...


Specifiesthemateriallibraryfileforthematerialdefinitionssetwiththeusemtlstatement.Youcanspecifymultiplefilenameswithmtllib.Ifmultiplefilenamesarespecified,thefirstfilelistedissearchedfirstforthematerialdefinition,thesecondfileissearchednext,andsoon.

WhenyouassignamateriallibraryusingtheModelprogram,onlyonemaplibraryper.objfileisallowed.Youcanassignmultiplelibrariesusingatexteditor.

filenameisthenameofthelibraryfilethatdefinesthematerials.Thereisnodefault.

shadow_objfilename


Specifiestheshadowobjectfilename.Thisobjectisusedtocastshadowsforthecurrentobject.Shadowsareonlyvisibleinarenderedimage;theycannotbeseenusinghardwareshading.The

shadowobjectisinvisibleexceptforitsshadow.

Anobjectwillcastshadowsonlyifithasashadowobject.Youcanuseanobjectasitsownshadowobject.However,asimplifiedversionoftheoriginalobjectisusuallypreferableforshadowobjects,sinceshadowcastingcangreatlyincreaserenderingtime.

filenameisthefilenamefortheshadowobject.Youcanenteranyvalidobjectfilenamefortheshadowobject.Theobjectfilecanbean.objor.modfile.Ifafilenameisgivenwithoutanextension,anextensionof.objisassumed.

Onlyoneshadowobjectcanbestoredinafile.Ifmorethanone

shadowobjectisspecified,thelastonespecifiedwillbeused.

trace_objfilename


Specifiestheraytracingobjectfilename.Thisobjectwillbeusedingeneratingreflectionsofthecurrentobjectonreflectivesurfaces.Reflectionsareonlyvisibleinarenderedimage;theycannotbeseenusinghardwareshading.

Anobjectwillappearinreflectionsonlyifithasatraceobject.Youcanuseanobjectasitsowntraceobject.However,a

simplifiedversionoftheoriginalobjectisusuallypreferablefortraceobjects,sinceraytracingcangreatlyincreaserenderingtime.

filenameisthefilenamefortheraytracingobject.Youcanenteranyvalidobjectfilenameforthetraceobject.Youcanenteranyvalidobjectfilenamefortheshadowobject.Theobjectfilecanbean.objor.modfile.Ifafilenameisgivenwithoutanextension,anextensionof.objisassumed.


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Onlyonetraceobjectcanbestoredinafile.Ifmorethanoneisspecified,thelastoneisused.

ctechtechniqueresolution


Specifiesacurveapproximationtechnique.Theargumentsspecifythetechniqueandresolutionforthecurve.

Youmustselectfromoneofthefollowingthreetechniques.

ctechcparmres

Specifiesacurvewithconstantparametricsubdivisionusingoneresolutionparameter.Eachpolynomialsegmentofthecurveissubdividedntimesinparameterspace,wherenistheresolutionparametermultipliedbythedegreeofthecurve.

resistheresolutionparameter.Thelargerthevalue,thefinertheresolution.Ifreshasavalueof0,eachpolynomialcurvesegmentisrepresentedbyasinglelinesegment.

ctechcspacemaxlength

Specifiesacurvewithconstantspatialsubdivision.Thecurveisapproximatedbyaseriesoflinesegmentswhoselengthsinrealspacearelessthanorequaltothemaxlength.

maxlengthisthemaximumlengthofthelinesegments.Thesmallerthevalue,thefinertheresolution.

ctechcurvmaxdistmaxangle

Specifiescurvature-dependentsubdivisionusingseparateresolutionparametersforthemaximumdistanceandthemaximumangle.

Thecurveisapproximatedbyaseriesoflinesegmentsinwhich1)thedistanceinobjectspacebetweenalinesegmentandtheactualcurvemustbelessthanthemaxdistparameterand2)theangleindegreesbetweentangentvectorsattheendsofalinesegmentmustbelessthanthemaxangleparameter.

maxdististhedistanceinrealspacebetweenalinesegmentandtheactualcurve.

maxangleistheangle(indegrees)betweentangentvectorsattheendsofalinesegment.

Thesmallerthevaluesformaxdistandmaxangle,thefinertheresolution.

NOTE:Approximationinformationfortrimming,hole,andspecialcurvesisstoredinthecorrespondingsurface.Thectechstatementforthesurfaceisused,notthectechstatementappliedtothecurv2statement.Althoughuntrimmedsurfaceshavenoexplicittrimmingloop,aloopisconstructedwhichboundsthelegalparameterrange.Thisimplicitloopfollowsthesamerulesasanyotherloopandisapproximatedaccordingtothectechinformation


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forthesurface.

stechtechniqueresolution


Specifiesasurfaceapproximationtechnique.Theargumentsspecifythetechniqueandresolutionforthesurface.

Youmustselectfromoneofthefollowingtechniques:

stechcparmauresvres

Specifiesasurfacewithconstantparametricsubdivisionusingseparateresolutionparametersfortheuandvdirections.Eachpatchofthesurfaceissubdividedntimesinparameterspace,wherenistheresolutionparametermultipliedbythedegreeofthesurface.

uresistheresolutionparameterfortheudirection.

vresistheresolutionparameterforthevdirection.

Thelargerthevaluesforuresandvres,thefinerthe

resolution.Ifyouenteravalueof0forbothuresandvres,eachpatchisapproximatedbytwotriangles.

stechcparmbuvres

Specifiesasurfacewithconstantparametricsubdivision,withrefinementusingoneresolutionparameterforboththeuandvdirections.

Aninitialtriangulationisperformedusingonlythepointsonthetrimmingcurves.Thistriangulationisthenrefineduntilalledgesareofanappropriatelength.Theresultingtrianglesarenotorientedalongisoparametriclinesastheyareinthe

cparmatechnique.

uvresistheresolutionparameterforboththeuandvdirections.Thelargerthevalue,thefinertheresolution.

stechcspacemaxlength

Specifiesasurfacewithconstantspatialsubdivision.

Thesurfaceissubdividedinrectangularregionsuntilthelengthinrealspaceofanyrectangleedgeislessthanthemaxlength.Theserectangularregionsarethentriangulated.

maxlengthisthelengthinrealspaceofanyrectangleedge.Thesmallerthevalue,thefinertheresolution.

stechcurvmaxdistmaxangle

Specifiesasurfacewithcurvature-dependentsubdivisionusingseparateresolutionparametersforthemaximumdistanceandthemaximumangle.

Thesurfaceissubdividedinrectangularregionsuntil1)the


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distanceinrealspacebetweentheapproximatingrectangleandtheactualsurfaceislessthanthemaxdist(approximately)and2)theangleindegreesbetweensurfacenormalsatthecornersoftherectangleislessthanthemaxangle.Followingsubdivision,theregionsaretriangulated.

maxdististhedistanceinrealspacebetweentheapproximatingrectangleandtheactualsurface.

maxangleistheangleindegreesbetweensurfacenormalsatthecornersoftherectangle.

Thesmallerthevaluesformaxdistandmaxangle,thefinertheresolution.

Examples

1.Cubewithmaterials

Thiscubehasadifferentmaterialappliedtoeachofitsfaces.

mtllibmaster.mtl

v0.0000002.0000002.000000

v0.0000000.0000002.000000v2.0000000.0000002.000000v2.0000002.0000002.000000v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000v2.0000002.0000000.000000#8vertices

gfrontusemtlredf1234gback

usemtlbluef8765grightusemtlgreenf4378gtopusemtlgoldf5148gleftusemtlorangef5621gbottomusemtlpurple

f2673#6elements

2.Cubecastingashadow

Inthisexample,thecubecastsashadowontheotherobjectswhenitisrenderedwithImage.Thecube,whichisstoredinthefilecube.obj,referencesitselfastheshadowobject.


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mtllibmaster.mtlshadow_objcube.obj

v0.0000002.0000002.000000v0.0000000.0000002.000000v2.0000000.0000002.000000v2.0000002.0000002.000000v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000v2.0000002.0000000.000000#8vertices

gfrontusemtlredf1234gbackusemtlbluef8765grightusemtlgreenf4378gtopusemtlgold

f5148gleftusemtlorangef5621gbottomusemtlpurplef2673#6elements

3.Cubecastingareflection

Thiscubecastsitsreflectiononanyreflectiveobjectswhenitis

renderedwithImage.Thecube,whichisstoredinthefilecube.obj,referencesitselfasthetraceobject.

mtllibmaster.mtltrace_objcube.obj

v0.0000002.0000002.000000v0.0000000.0000002.000000v2.0000000.0000002.000000v2.0000002.0000002.000000v0.0000002.0000000.000000v0.0000000.0000000.000000v2.0000000.0000000.000000

v2.0000002.0000000.000000#8vertices

gfrontusemtlredf1234gbackusemtlbluef8765gright


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usemtlgreenf4378gtopusemtlgoldf5148gleftusemtlorangef5621gbottomusemtlpurplef2673#6elements

4.Texture-mappedsquare

Thisexampledescribesa2x2square.Itismappedwitha1x1squaretexture.Thetextureisstretchedtofitthesquareexactly.

mtllibmaster.mtl

v0.0000002.0000000.000000v0.0000000.0000000.000000

v2.0000000.0000000.000000v2.0000002.0000000.000000vt0.0000001.0000000.000000vt0.0000000.0000000.000000vt1.0000000.0000000.000000vt1.0000001.0000000.000000#4vertices

usemtlwoodf1/12/23/34/4#1element

5.Approximationtechniqueforasurface

ThisexampleshowsaB-splinesurfacewhichwillbeapproximatedusingcurvature-dependentsubdivisionspecifiedbythestechcommand.

gbspatchv-5.000000-5.000000-7.808327v-5.000000-1.666667-7.808327v-5.0000001.666667-7.808327v-5.0000005.000000-7.808327v-1.666667-5.000000-7.808327v-1.666667-1.66666711.977780v-1.6666671.66666711.977780v-1.6666675.000000-7.808327

v1.666667-5.000000-7.808327v1.666667-1.66666711.977780v1.6666671.66666711.977780v1.6666675.000000-7.808327v5.000000-5.000000-7.808327v5.000000-1.666667-7.808327v5.0000001.666667-7.808327v5.0000005.000000-7.808327#16vertices


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gbspatchcstypebsplinestechcurv0.510.000000deg33surf0.0000001.0000000.0000001.0000001314\1516910111256781234parmu-3.000000-2.000000-1.0000000.000000\1.0000002.0000003.0000004.000000parmv-3.000000-2.000000-1.0000000.000000\1.0000002.0000003.0000004.000000end#1element

6.Approximationtechniqueforacurve

ThisexampleshowsaBeziercurvewhichwillbeapproximatedusingconstantparametricsubdivisionspecifiedbythectechcommand.

v-2.3000001.9500000.000000v-2.2000000.7900000.000000v-2.340000-1.5100000.000000v-1.530000-1.4900000.000000

v-0.720000-1.4700000.000000v-0.7800000.2300000.000000v0.0700000.2500000.000000v0.9200000.2700000.000000v0.800000-1.6100000.000000v1.620000-1.5900000.000000v2.440000-1.5700000.000000v2.6900000.6700000.000000v2.9000001.9800000.000000#13vertices

gdefaultcstypebezier

ctechcparm1.000000deg3curv0.0000004.00000012345678910\111213parmu0.0000001.0000002.0000003.000000\4.000000end#1element

Comments

Commentscanappearanywhereinan.objfile.Theyareusedtoannotatethefile;theyarenotprocessed.

Hereisanexample:

#thisisacomment

TheModelprogramautomaticallyinsertscommentswhenitcreates.objfiles.Forexample,itreportsthenumberofgeometricvertices,texturevertices,andvertexnormalsinafile.


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#4vertices#4texturevertices#4normals

Mathematicsforfree-formcurves/surfaces

[IapologizebutthissectionwillmakeabsolutelynosensewhatsoeverwithouttheequationsanddiagramsandtherewasjustnoeasywaytoincludetheminapureASCIIdocument.Youshouldprobablyjustskipaheadtothesection"Supersededstatements."-Jim]

Generalforms

Rationalandnon-rationalcurvesandsurfaces

Ingeneral,anynon-rationalcurvesegmentmaybewrittenas:

where

K+1isthenumberofcontrolpoints

diarethecontrolpoints

nisthedegreeofthecurve

Ni,n(t)arethedegreenbasisfunctions

Extendingthistothebivariatecase,anynon-rationalsurfacepatchmaybewrittenas:

where:

K1+1isthenumberofcontrolpointsintheudirection

K2+1isthenumberofcontrolpointsinthevdirection

di,jarethecontrolpoints

misthedegreeofthesurfaceintheudirection

nisthedegreeofthesurfaceinthevdirection

Ni,m(u)arethedegreembasisfunctionsintheudirection

Nj,n(v)arethedegreenbasisfunctionsinthevdirection

NOTE:Thefrontofthesurfaceisdefinedasthesidewheretheuparameterincreasestotherightandthevparameterincreasesupward.

Wemayextendthiscurvetotherationalcaseas:

wherewiaretheweightsassociatedwiththecontrolpointsdi.Similarly,arationalsurfacemaybeexpressedas:

wherewi,jaretheweightsassociatedwiththecontrolpointsdi,j.

NOTE:Ifacurveorsurfaceinan.objfileisrational,itmustuse


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theratoptionwiththecstypestatementanditrequiressomeweightvaluesforeachcontrolpoint.

Theweightsfortherationalformaregivenasathirdcontrolpointcoordinate(fortrimmingcurves)orfourthcoordinate(forspacecurvesandsurfaces).Theseweightsareoptionalanddefaultto1.0ifnotgiven.

Thisdefaultweightisonlyreasonableforcurvesandsurfaceswhosebasisfunctionssumto1.0,suchasBezier,Cardinal,andNURB.ItdoesnotmakesenseforTaylorandmayormaynotmakesenseforarepresentationgiveninbasis-matrixform.

ForallformsotherthanB-spline,thefinalcurveorsurfaceisconstructedbypiecingtogethertheindividualcurvesegmentsorsurfacepatches.Aglobalparameterspaceisthendefinedovertheentirecompositecurveorsurfaceusingtheparametervectorgivenwiththeparmstatement.

Theparametervectorforacurveisalistofpglobalparametervalues

{t1,...,tp}.Ift1t


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1.xixi+1,

2.x0


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withtheparmstatementmustbeK-n+2,whereKisthenumberofcontrolpoints.Forsurfaces,thisrequirementappliesindependentlyfortheuandvparametricdirections.

Taylor

TypetaylorspecifiesarbitrarydegreeTaylorpolynomialcurvesandsurfaces.Thebasisfunctionissimply:

NOTE:Thecontrolpointsinthiscasearethepolynomialcoefficientsandhavenoobviousgeometricsignificance.

Whenusingtypetaylor,thenumberofglobalparametervaluesgivenwiththeparmstatementmustbe(K+1)/(n+1)+1,whereKisthenumberofcontrolpoints.Forsurfaces,thisrequirementappliesindependentlyfortheuandvparametricdirections.

Basismatrix

Typebmatrixspecifiesgeneral,arbitrary-degreecurvesdefinedthroughtheuseofabasismatrixratherthananexplicittypesuchasBezier.Thebasisfunctionsaredefinedas:

wherethebasismatrixisthebi,j.Inordertomakethematrixnature

ofthismoreobvious,wemayalsowrite:

Whenconstructingbasismatrices,youshouldkeepthisdefinitioninmind,asdifferentauthorswritethisindifferentways.Amorecommonmatrixrepresentationis:

Tousesuchmatricesinthe.objfile,simplytransposethematrixandreversethecolumnordering.

Whenusingtypebasis,thenumberofglobalparametervaluesgivenwiththeparmstatementmustbe(K-n)/s+2,whereKisthenumberofcontrolpointsandsisthestepsizegivenwiththestepstatement.Forsurfaces,thisrequirementappliesindependentlyfortheuandv

parametricdirections.

Surfacevertexdata

Controlpoints

Thecontrolpointsforasurfaceconsistingofasinglepatcharelistedintheorderi=0toK1forj=0,followedbyi=0toK1forj=1,andsoonuntilj=K2.

Forsurfacesmadeupofmanypatches,whichistheusualcase,thecontrolpointsareorderedasifthesurfacewereasinglelargepatch.Forexample,thecontrolpointsforabicubicBeziersurfaceconsisting

offourpatcheswouldbearrangedasfollows:

where(m,n)istheglobalparameterspaceofthesurfaceandthenumbersindicatetheorderingofthevertexindicesinthesurfstatement.

Textureverticesandtexturemapping

Whentextureverticesarenotsupplied,theoriginalsurfaceparameterizationisusedfortexturemapping.However,iftexture


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verticesaresupplied,theyareinterpretedasadditionalinformationtobeinterpolatedorapproximatedseparatelyfrom,butusingthesameinterpolationfunctionsasthecontrolvertices.

Thatis,whereasthesurfaceitself,inthenon-rationalcase,wasgiveninthesection"Rationalandnon-rationalcurvesandsurfaces"as:

thetextureverticesareinterpolatedorapproximatedby:

whereti,jarethetextureverticesandthebasisfunctionsarethesameasforS(u,v).ItisT(u,v),ratherthanthesurfaceparameterization(u,v),whichisusedwhenatexturemapisapplied.

Vertexnormalsandnormalmapping

Vertexnormalsaretreatedexactlyliketexturevertices.Whenvertexnormalsarenotsupplied,thetruesurfacenormalsareused.Ifvertexnormalsaresupplied,theyarecalculatedas:

whereqi,jarethevertexnormalsandthebasisfunctionsarethesameasforS(u,v)andT(u,v).

NOTE:Vertexnormalsdonotaffecttheshapeofthesurface;theyaresimplyassociatedwiththetriangleverticesinthefinaltriangulation.Aswithfaces,supplyingvertexnormalsonlyaffectslightingcalculationsforthesurface.

Thetreatmentofbothtextureverticesandvertexnormalsinthecaseofrationalsurfacesisidentical.ItisimportanttonoticethatevenwhenthesurfaceS(u,v)isrational,thetextureandnormalsurfaces,T(u,v)andQ(u,v),arenotrational.Thisisbecausethecontrolpoints(thetextureverticesandvertexnormals)areneverrational.

Curveandsurfaceoperations

Specialpoints

Thefollowingequationsgiveamoreprecisedescriptionofspecialpointsforspacecurvesanddiscusstheextensiontotrimmingcurvesandsurfaces.

LetC(t)beaspacecurvewiththeglobalparametert.Wecanapproximatethiscurvebyasetofk-1linesegmentswhichconnectthepoints:

forsomesetofkglobalparametervalues{t1,...,tk}

Givenaspecialpointtsintheparameterspaceofthecurve(referencedbyvp),weguaranteethatts{t1,...,tk}.Morespecifically,weapproximatethecurveby:

where,atthepointiwheretsisinserted,wehavetits


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LetT(t)beaspecialcurvewiththeglobalparametert.Wehave:

where(m,n)isapointintheglobalparameterspaceofasurface.Wecanapproximatethiscurvebyasetofk-1linesegmentswhichconnectthepoints:

forsomesetofkglobalparametervalues.

LetS(m,n)beasurfacewiththeglobalparametersmandn.Wecanapproximatethissurfacebyatriangulationofasetofppoints.

whichlieonthesurface.WefurtherdefineEasthesetofalledgessuchthatei,jEimpliesthatS(mi,ni)andS(mj,nj)areconnectedinthetriangulation.Finally,weguaranteethatthereexistssomesubsetofE:

suchthatthepoints:

areconnectedinthetriangulation.

Connectivity

Recallthatthesyntaxoftheconstatementis:

consurf_1q0_1q1_1curv2d_1surf_2q0_2q1_2curv2d_2

Ifwelet:

T1(t1)bethecurvereferencedbycurv2d_1

S1(m1,n1)bethesurfacereferencedbysurf1onwhichT1(t1)lies

T2(t2)bethecurvereferencedbycurv2d_2

S2(m2,n2)bethesurfacereferencedbysurf2onwhichT2(t2)lies

thenS1(T1(t1)),S2(T2(t2))mustbeidenticaluptoreparameterization.Moreover,itmustbethecasethat:

S1(T1(q0_1))=S2(T2(q0_2))

and:

S1(T1(q1_1))=S2(T2(q1_2))

ItisalongthecurveS1(T1(t1))betweent1=q0_1andt1=q1_1,andthecurveS2(T2(t2))betweent2=q0_2andt2=q1_2thatthesurfaceS1(m1,n1)isconnectedtothesurfaceS2(m2,n2).

Supersededstatements

Thenew.objfileformathaseliminatedtheneedforseveralpatchandcurvestatements.Thesestatementshavebeenreplacedbyfree-formgeometrystatements.

Inthe3.0release,thefollowingkeywordshavebeensuperseded:


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obsp

obzp

ocdc

ocdp

ores

Youcanstillreadthesestatementsinthisversion3.0,however,thesystemwillnolongerwritefilesinthisformat.

Thisreleaseisthelastreleasethatwillreadthesestatements.Ifyouwanttosaveanydatafromthisformat,readinthefileandwriteitout.Thesystemwillconvertthedatatothenew.objformat.

Formoreinformationonthenewsyntaxstatements,see"Specifyingfree-formcurvesandsurfaces."

Syntax

Thefollowingsyntaxstatementsareforthesupersededkeywords.

bspv1v2...v16

SpecifiesaB-splinepatch.B-splinepatcheshavesixteencontrolpoints,definedasvertices.Onlyfourofthecontrolpointsaredistributedoverthesurfaceofthepatch;theremainderaredistributedaroundtheperimeterofthepatch.

PatchesmustbetessellatedinModelbeforetheycanbecorrectlyshadedorrendered.

visthevertexnumberforacontrolpoint.Sixteenvertexnumbersarerequired.Positivevaluesindicateabsolutevertexnumbers.Negativevaluesindicaterelativevertexnumbers.

bzpv1v2...v16

SpecifiesaBezierpatch.Bezierpatcheshavesixteencontrolpoints,definedasvertices.Thecontrolpointsaredistributeduniformlyoveritssurface.



cdcv1v2v3v4v5...

SpecifiesaCardinalcurve.Cardinalcurveshaveaminimumoffourcontrolpoints,definedasvertices.

Cardinalcurvescannotbecorrectlyshadedorrendered.TheycanbetessellatedandthenextrudedinModeltocreate3Dshapes.

visthevertexnumberforacontrolpoint.Aminimumoffour


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vertexnumbersarerequired.Thereisnolimitonthemaximum.Positivevaluesindicateabsolutevertexnumbers.Negativevaluesindicaterelativevertexnumbers.

cdpv1v2v3...v16

SpecifiesaCardinalpatch.Cardinalpatcheshavesixteencontrolpoints,definedasvertices.Fourofthecontrolpointsareattachedtothecornersofthepatch.



resusegvseg

Referenceanddisplaystatement.

SetsthenumberofsegmentsforBezier,B-splineandCardinalpatchesthatfollowit.

usegisthenumberofsegmentsintheudirection(horizontalorxdirection).Theminimumsettingis3andthemaximumsettingis120.Thedefaultis4.

vsegisthenumberofsegmentsinthevdirection(verticalorydirection).Theminimumsettingis3andthemaximumsettingis120.Thedefaultis4.

Comparisonof2.11and3.0syntax

Cardinalcurve

Thefollowingexampleshowsthe2.11syntaxandthe3.0syntaxforthe

sameCardinalcurve.

2.11Cardinalcurve

#2.11CardinalCurve

v2.5700001.2800000.000000v0.9400001.3400000.000000v-0.6700000.8200000.000000v-0.770000-0.9400000.000000v1.030000-1.3500000.000000v3.070000-1.3100000.000000#6vertices

cdc123456

3.0Cardinalcurve

#3.0Cardinalcurve

v2.5700001.2800000.000000v0.9400001.3400000.000000


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v-0.6700000.8200000.000000v-0.770000-0.9400000.000000v1.030000-1.3500000.000000v3.070000-1.3100000.000000#6vertices

cstypecardinaldeg3curv0.0000003.000000123456parmu0.0000001.0000002.0000003.000000end#1element

Bezierpatch

Thefollowingexampleshowsthe2.11syntaxandthe3.0syntaxforthesameBezierpatch.

2.11Bezierpatch

#2.11BezierPatchv-5.000000-5.0000000.000000v-5.000000-1.6666670.000000v-5.0000001.6666670.000000

v-5.0000005.0000000.000000v-1.666667-5.0000000.000000v-1.666667-1.6666670.000000v-1.6666671.6666670.000000v-1.6666675.0000000.000000v1.666667-5.0000000.000000v1.666667-1.6666670.000000v1.6666671.6666670.000000v1.6666675.0000000.000000v5.000000-5.0000000.000000v5.000000-1.6666670.000000v5.0000001.6666670.000000v5.0000005.0000000.000000

#16vertices

bzp12345678910111213141516#1element

3.0Bezierpatch

#3.0Bezierpatch

v-5.000000-5.0000000.000000v-5.000000-1.6666670.000000v-5.0000001.6666670.000000v-5.0000005.0000000.000000

v-1.666667-5.0000000.000000v-1.666667-1.6666670.000000v-1.6666671.6666670.000000v-1.6666675.0000000.000000v1.666667-5.0000000.000000v1.666667-1.6666670.000000v1.6666671.6666670.000000v1.6666675.0000000.000000v5.000000-5.0000000.000000v5.000000-1.6666670.000000


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v5.0000001.6666670.000000v5.0000005.0000000.000000#16vertices

cstypebezierdeg33surf0.0000001.0000000.0000001.0000001314\1516910111256781234parmu0.0000001.000000parmv0.0000001.000000end#1element

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