With so much focus on 3d, there does not appear to be as much attention to working with 2d imports. I work with a lot of DWG imports in my planning work, and I am pleased that AC provides several options for working with them:
If I only need the DWG for tracing and snapping, I find just dragging the DWG onto a worksheet (vs onto the floor plan) is a 'clean' way to work. Then, when I am anywhere in the model where I need it, I can right click on the worksheet in the Navigator and choose the 'Show As Trace Reference'. Its particularly useful if I'm modeling an existing structure from historical DWG and PDF files.
Other times, I want to simply include the entire 2d drawing in a published set in an as-is state (e.g., printing an existing condition drawing with the new project title block). I just drag the drawing onto the appropriate floor on a pre-set drawing layer, without exploding it. I then have that drawing layer visible for printing. (Alternately, here I may choose the x-ref option, if I think I will be frequently changing out the external DWGs with updated versions.)
Most often, though, I use the exploded option within the model. I find this option works well when I have access to fairly consistent drawings with rich content, but do not have the time to build an entire 3d model of a large existing building. For this application I want the 2d elements to substitute graphically like 3d objects (e.g., to produce 2d+3d drawings in color, apply renovation status, and so forth). To make that work, I start with a template which already contains a standard CAD layer set alongside my 3d set. Then, when I explode the drawing, I choose to embed the imported drawings layers and then delete the monolithic drawing I dragged in. I then go to my layer manager and move the 2d elements from non-standard layers to the standard layers. Once there, they will follow my LC and GORs, and I can apply all my AC settings. However, the clean-up can be a very quick or messy process, depending on the imported drawing quality, which is why many here discourage this option. It can be 10m to 30m per drawing, especially if it has a lot of rich content. Offsetting that, if I have several drawings from the same source (e.g., one drawing per floor plate), I can bring them all in, explode all, then use the layer manager to move elements once and the Find & Select tool to take care of the odd linework on each floor in turn, which speeds things along quite well.
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