Cad ala brep, csg and sweep representation gtu

gtu be mechanical
CAD Computer Aided Design
ppt ALA Sem 6th
B rep CSG & Sweep Representation

1. Computer Aided Design(2161903)
B.E. MECH –Sem VI
th
Prepared by,
NAME ENROLLMENT NO.
•PANDYA RUSHI R. 170953119024
•PARMAR RONAKKUMAR V. 170953119026
•PATEL DRUPAD H. 170953119027
•PATEL JEET R. 170953119029
•PATEL MEET M. 170953119030
•PATEL SHREY B. 170953119031
Guided by,
Asst. Prof. Jay Shah
(Mechanical Deptt)
Batch:-6B2 GroupNo :-B6

2. CONTENTS
•Boundary representation (B-REP)
–Topological and geometrical information of b-rep
–Advantages and disadvantages BOUNDARY REPRESENTATION
•Constructive solid geometry (CSG)
–Typical standard primitives
–Types of CSG schemes
–Advantages and disadvantages CONSTRUCTIVE SOLID GEOMETRY (CSG)
•Sweep representation
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3. BOUNDARY REPRESENTATION (B-REP)
•Insolidmodelingandcomputer-aideddesign,boundaryrepresentationisoften
abbreviatedasB-reporBREP.Itisamethodforrepresentingshapesusingthe
limits.
•Asolidisrepresentedasacollectionofconnectedsurfaceelements,the
boundarybetweensolidandnon-solid.
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4. •ModelsareamoreexplicitrepresentationthanCSG.Theobjectis
representedbyacomplicateddatastructuregivinginformationabout
eachoftheobject'sfaces,edgesandverticesandhowtheyarejoined
together.
•AppearstobeamorenaturalrepresentationforVisionsincesurface
informationisreadilyavailable.
•Thedescriptionoftheobjectcanbeintotwoparts:
Topology
•Recordtheconnectivityofthefaces,edgesandverticesbymeansofpointersinthedata
structure.
Geometry
•Describestheexactshapeandpositionofeachoftheedges,facesandvertices.
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5. TOPOLOGICAL AND GEOMETRICAL
INFORMATION OF B-REP
•Thedatabaseofaboundarymodelcontainsbothitstopologyandgeometry.
TPOLOGICAL DATA:-
•TopologyiscreatedbyperformingEuleroperationsandgeometryiscreatedby
performingEuclideancalculations.
•Euleroperationsareusedtocreate,manipulate,andeditthefaces,edges,and
verticesofaboundarymodelastheset(Boolean)operationscreate,manipulate,
andeditprimitivesofCSGmodels.
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6. GEOMETRIC DATA:-
•Itincludescoordinatesofvertices,rigidmotionandtransformation
(translation,rotation,etc.),andmetricinformationsuchasdistances,angles,
areas,volumes,andinertiatensors.
•Itshouldbenotedthattopologyandgeometryareinterrelatedandcannotbe
separatedentirely.Bothmustbecompatibleotherwisenonsenseobjectsmay
result.
•Figureshowsasquarewhich,afterdividingitstopedgesbyintroducinganew
vertex,isstillvalidtopologicallybutproducesanonsenseobjectdependingon
thegeometryofthenewvertex.
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•Computationaleffortsand
timerequiredtodisplay
modelsareless.
•Combainingwireframe
andsurfacemodelsare
possible.
•Complex engineering
modelscanbemodelled
easily.
•Thedatatobestoredismore
anditrequiresmorememory.
•Complexcurvesandsurfaces
areapproximated.

8. CONSTRUCTIVE SOLID GEOMETRY (CSG)
•Constructivesolidgeometry(CSG)(formerlycalledcomputational
binarysolidgeometry)isatechniqueusedinsolidmodeling.
•Constructivesolidgeometryallowsamodelertocreatea
complexsurfaceorobjectbyusingBooleanoperatorstocombine
simplerobjects.Potentiallygeneratingvisuallycomplexobjectsby
combiningafewprimitiveones.
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•Combinevolumeoccupiedby
overlapping3Dobjectsusingset
booleanoperationseachprimitive
isdefinedasacombinationofhalf-
spaces.
Typicalstandardprimitivesare:
•One,cylinder,sphere,torus,block,
closedsplinesurface,rightangular
wedge.sweptsolids(arevolution
orlinearsweepofaplanarface
whichmaycontainholes.
•Operationsareunion,intersection
anddifference.

10. TherearetwotypesofCSGschemes:-
•PrimitiveBasedCSG:
Itisbasedonboundedvalidsolidprimitives,r-sets.Itisthemostpopular
CSGscheme.
•HalfspaceBasedCSG:
Thisschemeusesunboundedhalfspaces(nonr-sets).Boundedsolid
primitivesareconsideredcompositehalfspacesandtheboundariesoftheseare
thesurfacesofthecomponenthalfspaces.
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•Good for describing many things,
particularly machined objects.
•Moderetlyintuitive and easy to
understand.
•Not good match for ploygon
renderes.
•Some objects are hard to describe.

12. SWEEP REPRESENTATION
•Solidmodelscanalsobebuiltupfromsweeps.Schemesbasedonsweep
representationareusefulincreatingsolidmodelsoftwo-and-a-half-
dimensionalobjects.
•Theclassoftwo-and-a-half-dimensionalobjectsincludesbothsolidsofuniform
thicknessinagivendirectionandaxisymmetricsolids.
•Theformerareknownasextrudedsolidsandarecreatedvialinearor
translationalsweep;thelatteraresolidsofrevolutionwhichcanbecreatedvia
rotationalsweep.
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13. •Sweepingisbasedonthenotionofmovingapoint,curve,orasurfacealonga
givenpath.
•Therearethreetypesofsweep:linear,nonlinear,andhybridsweeps.
•Inlinearsweep,thepathisalinearorcircularvectordescribedbyalinear,
mostoftenparametric,equationwhileinnonlinearsweep,thepathisacurve
describedbyahigher-orderequation(quadratic,cubic,orhigher).
•Hybridsweepcombineslinearand/ornonlinearsweepviasetoperationsand
is,therefore,ameansofincreasingthemodelingdomainofsweep
representations.
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•Linearsweepcanbedividedfurtherinto
translationalandrotationalsweep.
•Intranslationalsweep,aplanartwo-
dimensionalpointsetdescribedbyits
boundary(orcontour)canbemoveda
givendistanceinspaceinaperpendicular
direction(calledthedirectrix)tothe
planeoftheset.
•Nonlinearsweepissimilartolinear
sweepbutwiththedirectrixbeinga
curveinsteadofavector.Hybridsweep
tendstoutilizesomeformofset
operations.Figureshowsvarioustypesof
sweep:

15. THANK YOU
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