Import DXF File

Boundaries (Excavation, Ground Surface) and Stress Grids can be imported into Examine2D from a DXF file (AutoCAD Drawing Exchange File), using the Import DXF option in the Import sub-menu of the File menu. This allows users to import models created in AutoCAD, for example, into Examine2D.

Importing boundaries from a DXF file is equivalent to adding boundaries using the Add Excavation or Add Ground Surface options. That is, all the same rules apply, and boundaries will be automatically checked for validity, etc.

To import boundaries / stress grids from a DXF file:

Select Import DXF from the Import sub-menu of the File menu.
In the DXF Options dialog, select the entities you would like to import, using the checkboxes provided.
Select the Import button, and you will see an Open File dialog. Select the required DXF file and select OK, and all entities you selected in the DXF Options dialog will be imported into the current Examine2D document.

If boundaries already exist in your current Examine2D document when you use Import DXF, you may see a warning message if the imported boundaries are not compatible with existing boundaries. For example, if you try to import an Excavation which intersects an existing Excavation. So always be aware of what is in your DXF file when you try to import entities.

NOTE: if you are having problems trying to import a DXF file into Examine2D, make sure you read all of the information below.

Layer and Entity Types

If you are using AutoCAD to create DXF files for import into Examine2D, use the following conventions for layering and entity type:

Examine2D Object	Layer Name	AutoCAD Entity Type
Excavation Boundary	EXCAVATION	Closed LINE / POLYLINE
Ground Surface Boundary	GROUNDSURFACE	LINE / POLYLINE
Stress Grid	STRESSGRID	Closed LINE / POLYLINE

Importing Arcs from DXF Files

True circular arcs CANNOT be used to define boundaries in Examine2D. All boundaries in Examine2D are made up of linear segments connected by vertices.

However, if you import a DXF file which uses true arcs to define boundaries, Examine2D will automatically convert arcs into a series of linear segments, which approximate the arc.

By default, Examine2D will convert an arc from a DXF file into 16 line segments. This value can be customized by the user if desired, in the Preferences dialog. Select File > Preferences, enter a new value for DXF arc discretizations, and select OK. This value in the Preferences dialog will always be used to convert arcs read from DXF files.

DXF Epsilon

When you import a DXF file with multiple lines or polylines of the same layer type (e.g. EXCAVATION entities), Examine2D will automatically attempt to "piece together" individual entities to form larger polylines, if vertices overlap or are within a certain distance of each other. If two vertices are very close to each other, but have slightly different coordinates, Examine2D will automatically join the entities at that location, if the vertices are sufficiently close together.

The parameter which controls this automatic merging of vertices is the DXF Epsilon. The DXF Epsilon option can be found in the Preferences dialog in the File menu. The DXF Epsilon is a relative value, which defines the critical distance between vertices, as a fraction of the maximum extent of the model. If the distance between two vertices is less than the DXF Epsilon (multiplied by the maximum extent of the model), then the two entities will be merged at that location.

A default value of DXF Epsilon is automatically in effect, however, the value can be adjusted by the user, if the DXF file is not importing correctly. In some cases, this may help, although this should be considered an advanced option which is not commonly used. Before you adjust the DXF Epsilon value, you should go through all of the troubleshooting tips listed below.

Troubleshooting Problems with DXF Import

If you are having problems trying to import a DXF file into Examine2D, this may be due to one or more of the following issues:

Layer Names

Check that you are using the correct layer name for each entity. A summary of layer names for the various Examine2D entities is given in the table above.

Layer Assignment

Check that entities in the DXF file are assigned to the correct layer.

Excavation polyline not closed

In Examine2D Excavation boundaries must always be CLOSED (i.e. they must form a closed polygon with the first vertex equal to the last vertex). If excavations are not properly closed, you will not be able to import them into Examine2D.

Carefully examine your coordinate values to determine if this is the problem. Sometimes the coordinates of two vertices are very nearly equal, but are slightly different in the last decimal places. Check all vertex coordinates and make appropriate modifications to ensure that Excavation boundaries are continuous and closed.
If an Excavation boundary in a DXF file consists of multiple lines/plines, it is best to convert it into a single, closed polyline, before you try to import into Examine2D. Although Examine2D does attempt to join segments in a DXF file into larger polylines (see the DXF Epsilon discussion above), it is better if the user does this manually, rather than relying on the automatic capability of Examine2D.

Coordinates must be 2-dimensional and in the XY plane

Examine2D does NOT support the import of 3-dimensional geometry. All lines/polylines must be 2-dimensional and in the XY plane (Z=0). If you have 3-dimensional (x,y,z) coordinates or if you have 2D coordinates which are not in the XY plane (e.g. XZ or YZ), then you will have to apply appropriate conversions and/or rotations to obtain the desired 2D geometry.

User Coordinates

Examine2D does NOT support the import of entities defined by User Coordinate Systems (UCS). The DXF file reader will only read coordinates in the World Coordinate System (WCS) with the 2D geometry (polylines, lines) on the XY plane (Z=0).

Very large coordinates

If the absolute value of X and/or Y coordinates are very large, relative to the extents of the model, this may cause problems with DXF import due to numerical precision issues. Furthermore, even if the DXF import is successful, very large coordinates can lead to modeling difficulties and/or incorrect analysis results. If the X and/or Y coordinates in your DXF file are extremely large, then you should translate the entire model to the origin (0,0), to avoid potential problems. For example, if the Y coordinates of your model are around 100,000, then apply a translation which shifts the entire model by -100,000 on the Y-axis.

As a general guideline, the ratio of the maximum model coordinates divided by the maximum model dimensions (e.g. maximum X-coordinate divided by maximum horizontal extent), should be less than approximately 10,000. If this ratio is greater than 10,000, then numerical precision issues may occur, and the model should be translated closer to the origin (0,0).

Measurement Units

Make sure that your measurement units are either meters or feet, according to whether you are using metric or imperial units in Examine2D.

Importing Arcs

Importing arcs from DXF files was introduced in Examine2D version 7. See above for more information.

Too many closely spaced vertices

It often occurs that DXF polylines have a large number of unnecessary vertices (i.e. the geometry could be accurately defined with a much smaller number of vertices). Also, vertices are often located very close to each other, due to automatic creation of 2D sections from 3D geometry, or due to manual digitizing procedures.

Although there is no limit to the number of vertices which can be imported from a DXF file, it is a good idea to simplify the geometry as much as possible, by deleting unnecessary vertices, so that the geometry is accurately defined by a smaller number of vertices, and vertices are not extremely close to each other.

NOTE: this situation does not necessarily cause problems with the import of the DXF file. The geometry may import correctly. However, closely spaced vertices can cause modeling or analysis problems in Examine2D, and in the worst case, can lead to incorrect analysis results, or a model which does not compute at all.

Recommended DXF Import Procedure

If you have gone through the troubleshooting tips (above) and you are still having problems with trying to import DXF geometry into Examine2D, the following procedure is recommended.

In AutoCAD, save each boundary entity from the main DXF file, into its own separate DXF file, by using the dxf export option in AutoCAD to pick each entity you want to export.
Import the DXF files into Examine2D one at a time. Only have one box checked (e.g. Excavations) in the DXF Options dialog in Examine2D.
If you follow this simple procedure, this will often allow you to successfully import the DXF geometry into Examine2D, and identify the source of any problems.
You might want to practice this procedure, by starting simple just to get the process down. For example: draw a simple excavation boundary in AutoCAD, export it. Draw a ground surface boundary, export it. Now bring them into Examine2D in the same order, one at a time.

Save as DXF version 12

In some cases, it may help if you save the DXF file as (AutoCAD) version 12 or 13. However, this is not recommended unless you have tried all of the above options first.