Target objectSensorRobot/PlatformSimulation environmentSpatial representationView search spaceShape knowledgeView determinationPath planningTerminationPerformance evaluationStereo cameraMonocular cameraTime-of-Flight (ToF)Range sensor(unspecified)Ground mobile robotGround mobile robotwith robot armMicro aerial vehicle(MAV)Not consideredIn-houseGazeboOpenAI GymV-REP2D occupancy map3D occupancy mapwith probability3D TSDF3D point cloud3D surfacePlanar view space3D view spacePrior 3Dpre-scannedSurfacereconstructionNot consideredAngle visibility(incident angleconstraint)Frontier-basedexploration# of unknown voxelUnknown surfacegainSampling density onsurfaceVisual informationMachine learningReinforcementlearningInformation-theoretic(entropy reduction)Seen free spaceEnvironmentmodelingA* approachRRT approachInformation gain inedges/actionsNot consideredFixed # of operationCompletion based onground truthNegligibleimprovement/changeCompleteness(mesh/voxel orfeasible views)Visual completenessVisual trajectory path# of scansTimeDistance traveledVolume (explored)Surface (scancoverage)Entropy reducedQualityReconstruction errorSelf measurementonlyBuilding/Structure