One of the major differences between OpenRoads Designer and OpenBridge Modeler from the early days is that OBM recommended always starting in a 3D seed file, as opposed to starting in a 2D file for ORD. While a few users have successfully worked with OBM by starting with a 2D seed file, this was never a fully supported workflow from a programming perspective, even though the differences in the end result isn't very obvious for less developed bridge models.

We plan on enhancing OBM soon to support starting in 2D and retooling several commands to work natively in 2D and generate the fully linked and intelligent 3D model automatically. Starting with the 2023 release of OBM, we have started to separate out all of the 2D elements into a new 2D Model named Decoration Space. Currently this includes the beam layout, decorators for all bridge elements including deck, pier and abutment and related components, bearings and components, barriers, cross frames and diaphragms, support line text, etc. The support lines even though they look like they are purely 2D elements, they are still part of the 3D Model. There is also an OBM generated alignment decorator in the 2D Decoration space. Switching between the 2D and the 3D models is done through the Models icon on the Home tab, Primary group in the ribbon tool bar.

If this 2D/3D separation is not desired, you can uncomment this line in the OpenBridgeModeler.cfg file

#OBM_PLACE_DECORATION_IN_SEPARATE_2D_MODEL = FALSE

Please note that while working in the 2D decoration space, we are unable to perform some actions like editing beam definitions, place diaphragms or cross frames, or place bearings etc. As such at this time, it is recommended that users continue to work primarily in 3D for building the model and use the 2D as a byproduct producing the line work for production.

A couple of significant benefits of separating the 2D Decoration Space is that dimensioning and measuring is generally easier in 2D for most users not very experienced with working natively in 3D and reusing the 2D line work for plan production is very beneficial. As more and more projects adopt iTwin based workflows including design review tools in the cloud, full separation of 3D objects and 2D elements is desired.

If you are bringing in an older file created with an earlier version with a bridge already placed, there is no separation of 3D/2D in these files to maintain the integrity of these files. For a new file, the decoration space is created only when the Add Bridge command is used.