ASCII-Objects
The format „ASCII-Objects“ enables to import object geometry data from ASCII-files. Points, line-like and area-like polygons with an arbitrary number of coordinate points (x,y,z) can be imported. Objects which are defined in CadnaA as closed polygons are closed correctly on import.
The object geometry is addressed to the specified CadnaA-object on import, i.e. not requiring any later conversion of object types. Besides the line the import to start with, the delimiter of columns and the column assignment to coordinates (x,y,z) can be freely defined.
By using blank lines or by addressing an object-specific ID it is controlled whether several objects are generated by CadnaA on import or whether all imported points belong to a single object.
Dialog Options for ASCII-Import
Dialog options
Object Type
Select here the target object type. By default, the object type „Aux Polygon“ is selected.
Begin Import in Line
When the ASCII file header contains lines with irrelevant data the line number at which the import starts can be specified (line No.s 1 to 20). So, the text file does not require to be reedited externally before import.
Delimiter
By default, TAB or SPACE are supposed to be the delimiters for data columns. When no delimiter is activated also several tab stops or several blanks in a sequence will not be interpreted as new columns. In case a single or several delimiters are activated each of those will be interpreted as a column delimiter. By selecting the option „Other“ an arbitrary character can be entered as column separator.
Column Assignment
Address the data columns to the coordinates (x,y,z) by using the three list boxes. An empty line marks separate objects as long as no ID is used. As delimiter for decimals the point has to be used. Up to 20 columns can be addressed.
Via the list box „ID“ - if available - a column can be assigned to the attribute ID (default setting "none"). If an ID is assigned upon import, any new ID being different from the previous ID generates a new object (see section „Examples“).
Import only Section
When this option is activated a section in the CadnaA target file can be specified. Only those objects will be imported which are inside of the section specified.
Simplify Geo automatically
In order to reduce the amount of data - in special with terrain data - the geometry can be simplified on import. After activation, enter a horizontal and - if any - a vertical distance. When the perpendicular from a point onto the connecting line between neighboring points is smaller than the entered value this point will be deleted.
Preview of File
This part of the dialog shows the first lines of the selected ASCII file. Use this preview as a help when configuring the import options.
Preview of Points
This part of the dialog shows a preview of the points applying the import options as selected. In conjunction with the file preview it can be judged in a comfortable manner whether the present settings result in a correct import of the data before starting the actual import.
Button „Transformation“
Via the button „Transformation“ the object’s coordinate data can be transformed on import (see Coordinate Transformation).
Button „Predefined“
The button „Predefined“ offers to save the present settings on dialog Options for ASCII-Import. Select the command Save As from the context menu and enter a designation on dialog Save Settings.
The designations entered will be displayed when clicking on button „Predefined“. To select a setting click to it using the mouse. Via the sub-menu Delete the setting selected is deleted without confirmation prompt.
Examples
1 - Import of closed polygons
Starting point is an ASCII file (filename „buildings.txt“) with four columns delimited by TABs. Individual building polygons are separated by an empty line. Consider that a point has to be used as decimal delimiter. The column headings are not evaluated (option „Begin Import in Line“, here: 3). The first and the last point of each building correspond.
Example
Path: Examples\Import\ASCII_Objects\buildings.txt
Select from the menu File|Import the file type „ASCII-Objects“, select the file buildings.txt, and click the „Options“ button. Via the subsequent dialog the import filter is configured.
The import of the buildings starts in the third row. Columns are delimited by the TAB-key. The coordinates (x,y,z) result from columns No.s 1, 2, and 3. Comparing the previews „Preview of File“ and „Preview of Points“ indicates that with these settings the import will start with the first polygon point.
As the object coordinates may be laying outside of the limits click on dialog Options|Limits the button „Calc“. Afterwards, click on the symbol Zoom to limits on the CadnaA-toolbox to display all objects imported.
Note
Imagine the last point of each building polygon not being present. This would result in open building-polygons after import. In this case, convert the buildings into e.g aux-polygons first, and then back to buildings. (via Modify Objects|Convert to). This procedure will automatically close the building polygons.
2 - Import of open polygons using an ID
The ASCII file to be imported has four data columns, separated by semicolons from each other. The polygons are supposed to be terrain contour lines.
In this case, the file has no blank lines. Each new object is generated based on the ID assigned. In case the ID changes upon import, a new object is created.
Example
Path: Examples\Import\ASCII_Objects\ct_lines.txt
Select from the menu File|Import the file type „ASCII-Objects“, select the file „ct_lines.cna“, and click the „Options“-button. Via the subsequent dialog the import filter is configured.
The import of the contour lines starts in the 3rd row. Activate the option „Semicolon“ to use it as a delimiter. The identifier ID is on the 1st column while the (x,y,z)-coordinates result from columns No.s 2 to 4. Comparing the previews „Preview of File“ and „Preview of Points“ indicates that with these settings the import will start with the 1st polygon point.
In case nothing is displayed select the symbol „Zoom to Limits“ from the toolbox. This will arrange the limits so that all objects get displayed.