Viewing and Inspecting AutoCAD DWG Data: Handling Blocks

Introduction

How FME interprets your AutoCAD drawing file is largely dependent on which reader parameters are selected.

The common ways that we choose to read an AutoCAD drawing file are based on:

• How we want to group our entities (see Viewing and Inspecting AutoCAD DWG Data: Grouping Entities) and
• Whether or not we want to explode blocks.

In this article, we'll examine how to explode blocks. Specifically, we'll explore the Explode Blocks into Entities reader parameter. For more information, please see our Autodesk AutoCAD RealDWG DWG/DXF Reader Parameters documentation.

Step-by-step Instructions

Exploding Block Entities

Exploding blocks means that the block will be exploded into its component entities, such as text, lines, points, and so on. This is useful when you want to represent your block in FME as it would be seen in AutoCAD, for example, if you want to translate a DWG to PDF.

1. Start FME Data Inspector and Open the Dataset

Open FME Data Inspector and click Open Dataset, or use the File > Open Dataset menu option

In the Select Dataset to View dialog, select AutoCAD DWG/DXF for the Format and select the trafficsignals.dwg file as the Dataset.

Click on the Parameters button.

For Entity Options, enable Explode Blocks into Entities.

In the reader parameters for adding a DWG reader, you will see that there is a whole section devoted to 'Entity Options'. This section controls how certain entities are going to be handled as they are read by FME. The first option available is 'Explode Blocks into Entities'

After enabling this parameter, additional parameters are available:

These additional menu options allow you to select where you want these component entities to be stored.

Click OK twice.

2. Examine Block

Zoom in on a single traffic light. The exploded blocks are in white. To see them more clearly, you may need to change the background color to black. To do this, click the Background button on the toolbar and select a color.

Here is an example of an exploded block. The block appears as it was drawn initially in AutoCAD, but the individual parts can be selected. That is because the block is no longer a single entity.

Preserving (Not Exploding) Block Entities

By not exploding block entities, we preserve the block's insert location (where it was placed in the model). If you are not concerned with maintaining the block's appearance as it looked in AutoCAD but rather want to retain a discrete entity with associated attributes (such as converting the AutoCAD blocks to points in an Esri Shapefile), then this is a great option.

You can do this by repeating the steps from the section above, but ensuring that ‘Explode Blocks into Entities’ is not enabled.

Below is an example of an unexploded block. If the reader parameter option "Explode Blocks into Entities" is not enabled, the block is represented as a single point. 

Data Attribution

The data used here originates from open data made available by the City of Vancouver, British Columbia. It contains information licensed under the Open Government License - Vancouver.