1 Overview Since its introduction in 1982, AutoCAD, developed by Autodesk of the United States, has been recognized for its ease of use, functionality, and openness. It has become the preferred CAD system in various engineering fields, including water conservancy and hydropower projects. Over the years, the use of AutoCAD for secondary development has led to significant achievements, such as the hydropower station ground-floor plant CAD system, gravity dam CAD system, tunnel CAD system, and others. These systems have proven effective in practical applications. However, the complexity of hydropower engineering design often exceeds the capabilities of off-the-shelf CAD software. Many challenges can only be addressed through customized solutions. This paper explores the application of the Lisp language in AutoCAD's secondary development, particularly in hydropower engineering design. Through several examples, it aims to demonstrate how Lisp can enhance efficiency and flexibility in the design process. Visual Lisp, introduced with AutoCAD R14, is a powerful development environment that integrates seamlessly with AutoCAD. It allows developers to create new commands and extend AutoCAD's capabilities efficiently. With AutoLisp, users can automate repetitive tasks, streamline workflows, and improve overall productivity in design projects. 2 Application Examples 2.1 Coordinate Drawing Line One common task in design work is drawing lines based on known coordinate points. For instance, data from river sections, embankments, or elevation curves can be converted into coordinate points. Using Excel, you can generate these points automatically. The next step is to use them in AutoCAD to draw lines. (1) Using script files (.SCR): Create a plain text file named EX1.SCR with comma-separated coordinates. Save the file and run it using the "Run Script" command in AutoCAD. This will automatically draw the lines. (2) Using LSP procedures: Create a file named EX2.DAT with multiple segments and curve names. The LSP program reads the file and draws the curves accordingly. This method offers more flexibility and control over the drawing process. 2.2 Sectional Cross-Section In hydropower projects, creating cross-sections from topographic maps is a frequent task. Visual Lisp simplifies this process. First, convert LWPOLYLINE and SPLINE entities to LINE for faster processing. Then, use the inters function to find intersection points between the section line and the topographic map. Calculate distances and heights to generate the cross-sectional profile. 2.3 Marking Along Curves Labeling along curves is another common requirement. Whether it's marking excavation lines, rock symbols, or Chinese characters, AutoCAD’s Measure or Divide commands are useful. You can also write custom LSP procedures to place labels along arbitrary curves, ensuring accuracy and consistency. 2.4 Form Generation AutoCAD lacks built-in table functions, but tables can be generated using LSP procedures. Input parameters like rows, columns, and dimensions, and the program creates a table with formatted text. This approach provides more control than directly pasting tables from Excel or Word. 2.5 Elevation Decimal Places Processing Adjusting decimal places in elevations or other numerical values can be tedious manually. An LSP procedure automates this task. Select the numbers, specify the desired decimal places, and the program updates all selected values instantly. 2.6 Pre- and Post-Processing Software Integration For complex engineering software like STES (plane seepage analysis), pre-processing involves generating node and element data, while post-processing includes visualizing results like equipotential lines. LSP scripts can automate these steps, making the workflow more efficient and reducing manual effort. 3 Conclusion AutoCAD has become an essential tool in design units worldwide. The introduction of Visual Lisp has significantly enhanced programming efficiency and the overall application level of AutoCAD. The examples discussed in this paper demonstrate the real-world impact of integrating Lisp-based tools into engineering design. By combining professional needs with simple yet powerful Lisp applets, designers can reduce workload, transform AutoCAD from a mere drawing tool into a comprehensive design platform, and ultimately improve project outcomes. Aluminium Profile,Extruded Aluminium Profile,Extruded Alu Profile,Alu Extrusions Profiles,Aluminium alloy Jiangsu Yuejia Metallic Technology Co.,Ltd , https://www.yuejiametal.com