ADAMS的CSG实体介绍

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1、WhatisConstructiveSolidGeometry?Contents1.0Introduction:IntelligentGeometry2.0ConstructiveSolidGeometryDefined3.0ConstructiveSolidGeometryinAction3.1BasicCSGOperations3.2IntermediateCSGOperations3.3AdvancedCSGOperations4.0Conclusion1.0Introduction:IntelligentGeometryConstructivesolidgeomet

2、ry(CSG)isatypeofintelligentgeometrythatgivestheprogrammerextrainformation.CSGusessimpleobjectscalled“solids”,constructedaccordingtogeometricrules.ThespecialpropertiesofCSGsolidsallowmathematicaloperationsthatarenotpossiblewithanarbitrarypolygonmesh.It’snowonderthatgameslikeHalf-Life2,Doom3

3、,andUnrealTournament2004relyonCSGasthebasisoftheirworldgeometry.2.0ConstructiveSolidGeometryDefinedCSGsolidsaresimpleconvexobjects,madeoutofintersectingcoplanarfaces:Convexmeansthatallfacespointoutawayfromeachother:Coplanarmeansthatalltheverticesofafaceliealongthesameplane:Thetoprightverte

4、xhasbeenmovedinwardstomaketheselectedfacenon-coplanar.Concaveobjectscanbecreatedusingmultipleconvexsolids:ThisconcavesolidstillfollowstherulesofCSG;eachindividualsolidisconvex.3.0ConstructiveSolidGeometryInActionThespecialpropertiesofCSGsolidsallowmathematicaloperationsthatarenotpossiblewi

5、thanarbitrarypolygonmesh.CSGsolidsaremadeoutofintersectingcoplanarfaces.Eachfacehasanascertainableplaneequation,definedasa3Dvector,plusadistancefromtheorigin:Eachfacehasanormalindicatingthedirectionitpoints,andadistancefromtheorigin.Theintersectionoftheplanesdefinesthesolid.3.1BasicCSGOper

6、ationsTwoequationsformthebasisofmorecomplexoperations.EquationfordistancebetweenapointandaplaneThesignoftheresultindicateswhetherthepointisinfrontoforbehindtheplane.DistancebetweenpointAandplaneB=(Bd–Bnx*Ax–Bny*Ay–Bnz*Az)Equationforray-planeintersectionDeterminestheintersectionpointofaline

7、in3Dspacewithaplane.IntersectionofrayABwithplaneC:u=(-Cnx*Ax–Cny*Ay–Cnz*Az+d)/(-Cnx*(Ax–Bx)–Cny*(Ay–By)–Cnz*(Az–Bz))x=Ax+(Bx-Ax)*uy=Ay+(By-Ay)*uz=Az+(Bz-Az)*u3.2IntermediateCSGOperationsIntermediateoperationsbasedonbasicCSGoperationscanbeusefulduringruntime,an