AutoCAD has been one of the most preferred software for all Computer Aided Drafting requirements. All these years it has been used as a software to draw geometries that represent the actual conditions but have we ever thought what goes behind all these or how these commands work or how can we get so many variable options for drafting. As an answer to this, the very first thing that comes to the mind is programming. Programming a computer is like giving a set of instructions to every action that might be impossible or too slow to be performed by a human. Now even for AutoCAD, many programs have been written as a result of which we have this automated software to design. For the purpose, LISP- a programming language was selected because it was a very high level language yet easy to adapt to and a perfect choice to automate the unstructured aspects of AutoCAD. Let us dive deeper into what this language is and how it has played an important role in automating AutoCAD.
What is LISP?
John McCarthy created the programming language and paradigm known as LISP (list processing) in 1958. It is the second-oldest high-level programming language in existence, and unlike statements and subroutines, it is structured around expressions and functions. Generally speaking, LISP was created as a useful mathematical notation for computer programmes, but as a result of its widespread use, it evolved into a well-liked programming language for AI (artificial intelligence). Every LISP job is a function, and the value it returns is a data object. This computer language has influenced the creation of other languages and offers a variety of dialects. AutoLISP, one of its numerous dialects, was created especially for use with AutoCAD.
How AutoLISP works?
AutoLISP is a dynamically scoped and typed LISP language with automatic memory management, settable symbols, and immutable list structure along with record definition facilities, arrays, and functions with a variable number of arguments. AUTOLISP’s main use lies in altering the graphical entities in AutoCAD, accessing internal DWG database and geometry apart from the core language. AutoLISP is given information about these graphical entity features in the form of association lists, where values are matched with AutoCAD group codes that denote characteristics like definitional points, radii, colours, layers, linetypes, etc. AutoCAD loads AutoLISP code from .LSP file format that contains program code in the form of plain text.
- Adding C before the intended function turns it into a command which can be entered in the command prompt to run.
- Function – defun, is a pre-defined set of instructions which are to be performed and these are further divided into 3 parts- OPERATOR, ARGUMENT AND COMMAND.
- Then comes charting wherein it is either written or drawn whatever the commands needs to do.
- After these basic functions comes the variables that store data in forms of letters or numbers.
- Using all of these, structuring for the code is done by adding symbols, variables and functions.
- This entire process is further enclosed by parentheses ().
So above process is how the basic programming can be done for any command. Other codes can also be designed wherein variables are assigned which we see as options when we give commands in AutoCAD.
Use of AutoLISP to customize commands in AutoCAD and its advantages.
By establishing unique instructions and modifying the values of system variables, AutoLISP enables the control and customization of the drawing environment. It is recommended that you give your custom commands names that make them easy to recognise. Custom variable properties can be assigned to a function, which can then be converted into instructions as necessary. These commands can be loaded in .LSP format. The users gain various advantages from this customization, including:
- Maintaining standards for designs and automating tiresome tasks in Professional AutoCAD Drafting.
- Panels, palettes, tool sets, and ribbon tabs can all be added to the workspace.
- It is possible to change graphic items, define system variables, include outside software, and more.
Integrating these automated processes with Building Information Modeling (BIM) in today’s complex construction environment can unlock even more significant benefits. BIM goes beyond simple drafting, offering a comprehensive approach to managing project data and collaboration. By leveraging BIM services, you can ensure seamless coordination between design, engineering, and construction, reducing errors, improved communication, and significant cost savings.
Use of AutoLISP in automating the repetitive task and extending functionality
If a polyline needs to be drawn but already has a specific line type assigned, rather than a variable, this can be accomplished by undefining the POLYLINE command and replacing/modifying it as necessary. Similar to command sets, layers, and quick access tools, they may all be modified to meet specific needs. Many years after Auto LISP’s introduction, it continued to be developed until the late 1990s, at which point Vital-LISP, a more modernised version of AutoLISP, was created with a number of features that AutoLISP did not have. After purchasing it, Autodesk changed the name to Visual-LISP. Up until the late 1999s, Visual-LISP was developed; following that, Autodesk focused on creating different coding environments for AutoCAD modification. There will always be other languages with enhanced tools but AutoLISP remains the most used as it is the easiest language to learn and run compared to any other coding languages which is why it is still in use.
Advantages of AutoLISP
- It can carry out intricate calculations.
- It has the ability to create, read, and modify files while interacting with the user and taking input.
- It can alter current drawings or perhaps create new ones entirely.
- It can run programmes other than AutoCAD and is compatible with every platform that runs AutoCAD.
- It can be tried directly from the AutoCAD command prompt.
AutoLISP has a collection of faults that aid in debugging the programme code.We can use codes to communicate with AutoCAD’s graphical editor with the aid of some basic programming skills. This feasibility of the language helps it make easy to use, extending the software’s functionality while making it more efficient and user-type specific. Almost all the activities that are done manually can be performed automatically with AutoLISP.
Conclusion
AutoLISP has proved to be a very simple and practical programming language to learn for designers or any other professional from a similar field. One of the major factors that make this language so favourable is that no major programming language knowledge is necessary other than basic coding and programming knowledge. AutoLISP is much easier to learn once the user gets familiar with the unending parenthesis making it very favourable to use. The only necessity to learn this language is to have a working knowledge of the software program that is being used and to be able to customize it as per the sole purpose and having learnt this we can modify many other languages.
