	Product:	MicroStation
	Version:	V8i, CONNECT
	Environment:	N\A
	Area:	DWG
	Subarea:	General

The purpose of this article to explain how to create Layout Viewports in a DWG file using MicroStation. First you will need to understand what a viewport is. Next you need to understand the limitations of the DWG file format and how they affect viewport. Then you can understand how to create viewports using MicroStation.

What is a Viewport?

There are actually two types of viewports in the DWG file format. The Model Viewport and the Layout Viewport. This article is only covering the Layout Viewport. The Layout Viewport can only be found in a paper space layout (sheet model) of the DWG file. You can think of the Viewport as a window frame or portal that allows the elements in the model space (design model) to be displayed in the paper space layout (sheet model). I relate this to placing a sheet of paper over my model and cutting a hole in the sheet of paper so that you can look through the hole and see the model. Keep in mind that you are looking directly at the model and not a picture or reference of the model.

What limitations of the DWG file format need to be considered?

The DWG format only supports one model space (design model)
The layout viewport can only be created in a paper space layout (sheet model).
The viewport only displays elements shown in the model space (design model) of the same file.
Any layers (levels) turned off globally or globally frozen are turned off throughout the file including in the viewport.
You cannot rotate the view in a paper space layout (sheet model)

Creating a viewport in a DWG file

You need to keep in mind what the eventual outcome is that you are trying to achieve. You want the elements in model space (design model) to be displayed in the paper space layout (sheet model). The way to accomplish this in MicroStation is to reference the Default Design Model directly into a Sheet Model in the same file. You can use the normal references tools to position the reference on the paper, scale it, clip it or rotate the reference. When the DWG drawing file is saved, the reference is wrote to the file as a viewport. Any other references from external files will not be used to create a viewport and will remain as a reference.

Creating a viewport when converting a MicroStation file to a DWG file

Again, you need to keep in mind what the eventual outcome is that you are trying to achieve, along with the limitations of the DWG file format. Since the DWG file format that you eventually want to go to only supports one Model Space (design model), you want to create the design in the Default Design Model. The Default Design Model is corresponding to the DWG Model Space. You can then reference the Default Design Model into a Sheet Model in the same file. You can have more than one sheet model in the file and it does not matter which sheet model you reference into as long as it is in the same file as the Default Design Model being referenced. You can use the normal references tools to position the reference on the paper, scale it, clip it or rotate the reference. Do not rotate the view in the sheet model, this is not supported in the DWG file format. When the MicroStation drawing file is converted to a DWG drawing, the Default Design Model that is referenced into the Sheet Model, of the same file, is wrote to the DWG file as a viewport. Any other references from any model other than the Default Design Model of the same file will not be used to create a viewport. They will be converted according to the settings in the Save As DWG Options.

Helpful Hints

The DWG file does have some limitations that don’t exist in the MicroStation file format. It is highly recommended that if the drawing is eventually going to be a DWG file, you should always work within the Limitations of the DWG file format.
MicroStation includes a DWG Workmode that disables some advanced MicroStation functionality to ensure that you do not create DWG-incompatible features.
DWG workmode is automatically enabled when a DWG file is opened.
When you are working in a DGN file, you can also manually set the workmode to DWG. Set the variable MS_WORKMODE = DWG.

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Original Author:

Rick Ruth