Overriding default CAD output
You can override the default output of the Export To CAD tool and generate drawings that conform to specific standards. The methods available to you fall into two basic categories: table-driven and template-driven. A third strategy uses both table data and a CAD template to generate custom objects such as AutoCAD blocks. The methods that work best will vary depending on your workflows, resources, and scope of the output requirements.
Examples of overriding the default output include the following:
- Exporting features to CAD drawings that conform to a uniform standard such as ISO or the U.S. National CAD Standard.
- Exporting attribute field values as CAD text.
- Including standard page layout elements such as title blocks or legends.
- Exporting point features and attribute values as AutoCAD blocks.
Reserved CAD fields
Reserved CAD fields are special fields you can add to a feature class to tell the Export To CAD tool how to create a particular CAD feature. Some fields are used individually, while others require companion fields to specify parameters. ArcGIS for Desktop includes a range of fields and keywords that enable you to control how geometry and text, layers, and attributes are generated. You can also redirect individual features to specific CAD drawings.
All workflows that use reserved CAD fields start with a common task sequence: add the field, then calculate the field with a valid keyword. Generally, Field Calculator is the most efficient way to do this. You can add these fields directly to the feature class table or manage them in a stand-alone table and join it to the feature layer. You can choose to create them manually or in an automated fashion with the Add CAD Fields tool.
Drawing layers
A set of fields reserved for drawing layers gives you the ability to specify names, color, line type, and other related properties. The keywords must be valid property values for the target application. For example, the color property in an AutoCAD drawing is defined using a fixed palette of 250 integers starting at 1 for the color red, whereas MicroStation files support custom color tables such that the color 1 may be red in one file, but blue in another.
Geometry and text
The field named CADType generates a range of (DWG) entities and (DGN) elements. You can use it to perform simple substitutions such as generating 3D polylines in an AutoCAD drawing instead of the default 2D polyline LWPOLYLINE. In addition to generating different geometry types, other fields in this category enable you to control their properties, such as color, line type, scale, and angular position.
You can also use the CADType field to recast point features as other, but equally valid, CAD objects, such as text or AutoCAD blocks. Generally, using the CADType field in this way requires one or more additional fields to specify required parameters. For example, when you recast a point feature as CAD text by using the keyword TEXT, you must also add the field TxtValue and specify the actual text string.
Seed files
You can specify one seed file per tool execution and use it to define layers, styles and settings, and native CAD objects such as AutoCAD blocks. The seed file can also contain page layout elements, such as title blocks and legends, and other base data that you want to include in the output CAD drawing. The results are similar to appending the input features to a copy of the seed file.
Drawing layers
As an alternative to adding the reserved CAD field Layer to the input feature class table, you can use a seed file to define the destination layers of the input features. By default, input features are exported to the seed file's drawing layers whose names match the input feature class or layer name.
Exporting point features as AutoCAD blocks
You can use AutoCAD block definitions stored in a seed file to generate point features in the output CAD drawing. This is accomplished by adding the reserved CAD fields CADType and RefName to the input point feature class table and calculating them to specify the entity type "INSERT" and the AutoCAD block name, respectively. By default, the feature attributes for any field heading that matches a block attribute (tag name) is also exported to the block as a block attribute. The block's insertion point defines its coordinate location.