Coordinate Lisp in AutoCAD
Using a Coordinate Lisp in AutoCAD
A coordinate Lisp routine in AutoCAD is a powerful tool to
streamline workflows involving point coordinates. It allows users to automate
the extraction, input, or manipulation of coordinates in a drawing, saving time
and reducing errors.
This article explains the concept, usage, and implementation
of a coordinate Lisp in AutoCAD.
1. What is a Coordinate Lisp?
A coordinate Lisp routine is a custom script that interacts
with points or objects in AutoCAD. It typically handles tasks such as:
- Extracting point coordinates from selected objects (e.g.,
polylines, points, circles).
- Inserting points or blocks at specific coordinates.
- Exporting coordinates to a file (e.g., CSV, TXT).
- Importing coordinates from external files.
2. Benefits of Using Coordinate Lisp
Time-saving: Automates repetitive tasks.
Accuracy: Reduces manual errors in coordinate handling.
Versatility: Handles various coordinate-related workflows,
from surveys to GIS data integration.
3. A Sample Coordinate Lisp
Below is an example of a Lisp routine for exporting the
coordinates of selected points or objects:
#Code: Export Coordinates
```lisp
(defun c:ExportCoords (/ selSet obj pt coordList fileName
file)
;; Prompt the user
to select points or objects
(prompt
"\nSelect points or objects: ")
(setq selSet (ssget
'((0 . "POINT,CIRCLE,LWPOLYLINE")))) ; Filter for valid objects
(if selSet
(progn
;; Loop through
the selection set
(setq coordList
nil)
(repeat (setq i
(sslength selSet))
(setq obj
(vlax-ename->vla-object (ssname selSet (setq i (1- i)))))
;; Get
coordinates based on object type
(cond
;; For
points
((=
(vla-get-ObjectName obj) "AcDbPoint")
(setq pt
(vlax-get obj 'Position)))
;; For
circles
((=
(vla-get-ObjectName obj) "AcDbCircle")
(setq pt
(vlax-get obj 'Center)))
;; For
polylines (start point as an example)
((=
(vla-get-ObjectName obj) "AcDbPolyline")
(setq pt
(vlax-get obj 'StartPoint)))
)
;; Add the
coordinates to the list
(setq
coordList (cons (strcat (rtos (car pt) 2 2) ","
(rtos
(cadr pt) 2 2)) coordList))
)
;; Save to file
(setq fileName
(getfiled "Save Coordinates to File" "" "txt" 1))
(if fileName
(progn
(setq file
(open fileName "w"))
(foreach
coord coordList
(write-line coord file)
)
(close file)
(princ
(strcat "\nCoordinates saved to file: " fileName))
)
)
)
(prompt "\nNo
valid objects selected.")
)
;; End the routine
(princ)
)
```
4. How the Lisp Works
1. Selection:
The routine prompts
you to select points or objects (e.g., points, circles, polylines).
2. Coordinate Extraction:
Based on the object
type:
Points: Extract
the position.
Circles: Extract
the center point.
Polylines: Extract
the start point (can be customized).
3. Export:
The extracted
coordinates are saved to a text file in `X,Y` format.
4. Command Execution:
Run the routine by
typing `ExportCoords` in the command line.
5. Using a Coordinate Lisp
1. Load the Lisp:
Save the Lisp code
as a `.lsp` file (e.g., `ExportCoords.lsp`).
Use the `APPLOAD`
command in AutoCAD to load the file.
Optionally, add the
Lisp to your startup suite for automatic loading.
2. Execute the Command:
Type `ExportCoords`
in the command line and follow the prompts.
3. Output:
The routine will
generate a text file with the coordinates of the selected objects.
6. Enhancing the Lisp
Import Coordinates:
Add functionality to
read coordinates from a file and place points or blocks at those locations.
3D Coordinates:
Modify the script to
handle `Z` values for 3D workflows.
File Formats:
Extend support to
formats like CSV or Excel-compatible files.
7. Example Applications
Surveying: Export surveyed points to a GIS or CAD system.
Engineering: Use coordinate lists for designing layouts.
Mapping: Import/export data to integrate with GIS platforms.
8. Troubleshooting
Objects Not Recognized:
Ensure the filter
(`(0 . "POINT,CIRCLE,LWPOLYLINE")`) matches the object types in the
drawing.
File Save Issues:
Verify write
permissions in the directory where the file is saved.
Conclusion
Coordinate Lisp routines in AutoCAD simplify workflows involving point data, especially in surveying, mapping, and engineering. By using scripts like the one described, you can save time and ensure precise data handling. Let me know if you’d like further enhancements or additional features!
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