Document Information

Document Type: TechNote 

Legacy Document Number:  8237

Overview

Note: For purposes of this document the terms "Shared Cell Instance" and "AutoCAD Block Insert" are interchangeable, the same is true for the terms Levels and Layers or "Default Level" and "Layer 0".

In versions of MicroStation prior to V8, the level of a shared cell instance was significant only for Point Cells, or cells that were placed as Relative. For Point Cells, the shared cell level is used to override the level of components, for cells placed in Relative mode, the levels of the components are determined relative to the shared cell level.

For AutoCAD and MicroStation V8, the level of the shared cell instances is also used when a component of the cell is placed on the "Default" (AutoCAD Layer"0") level the component will inherit the level of the shared cell instance. This is a long-time AutoCAD concept that can also be useful in a purely DGN environment. It allows the creator of a cell to combine components that inherit the active level (and symbology) as in a point cell with components that have fixed levels and symbologies.

In MicroStation V8 versions (prior to 08.00.02.02) the shared cell instance was only set to the active level for Point Cells and when Relative placement mode was selected, otherwise the instance level was somewhat arbitrarily set to the lowest component level within the cell. This is undesirable because it makes it impossible to control the level that the Default (Layer 0) components inherit. Furthermore DWG Blocks are implicitly graphics cells and Relative Placement mode is not supported under DWG workmode, so the only way to control shared cell instance level is to place the cell and then change the instance level from the Element Information dialog.

In 08.00.02.02 and beyond we will change the behavior for placing shared cell instances such that the instance always receives the active level (as it already does for Point and Relatively placed cells). This should cause no apparent change for shared cells placed from existing cell libraries, but will enable the efficient use of DWG Blocks or cells created in V8 with components on the default level.

Note: Another more subtle use of the Shared Cell Instance Level has to do with the handling of levels with the Frozen attribute set. Shared Cell Instances on a Frozen layer will be omitted completely even if the levels for the components are neither frozen or off. This differs from a level with display off as the shared cell components may still display even if a shared cell's level is turned off.

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