API Reference > imodeljs-backend > ViewDefinitions ViewDefinitions Classes for working with elements that define what appears in views. See the learning articles. Classes Name Description AuxCoordSystem An auxiliary coordinate system element. AuxCoordSystem2d A 2d auxiliary coordinate system. AuxCoordSystem3d A 3d auxiliary coordinate system. AuxCoordSystemSpatial A spatial auxiliary coordinate system. CategorySelector Holds a list of Ids of Categories to be displayed in a view. DisplayStyle A DisplayStyle defines the parameters for 'styling' the contents of a view. DisplayStyle2d A DisplayStyle for 2d views. DisplayStyle3d A DisplayStyle for 3d views. DrawingViewDefinition Defines a view of a DrawingModel. ModelSelector Holds the list of Ids of GeometricModels displayed by a SpatialViewDefinition. OrthographicViewDefinition Defines a spatial view that displays geometry on the image plane using a parallel orthographic projection. SheetViewDefinition Defines a view of a SheetModel. SpatialViewDefinition Defines a view of one or more SpatialModels. ViewAttachment Represents an attachment of a ViewDefinition to a Sheet. ViewDefinition The definition element for a view. ViewDefinition2d Defines a view of a single 2d model. ViewDefinition3d Defines a view of one or more 3d models. Interfaces Name Description DisplayStyleCreationOptions Describes initial settings for a new DisplayStyle3d. Last Updated: 03 July, 2021