computer science

ObjectARX

ObjectARX is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand ObjectARX rather than just read about it. In short: ObjectARX (AutoCAD Runtime eXtension) is an API for customizing and extending AutoCAD. The ObjectARX SDK is published by Autodesk and freely available under license from Autodesk.

Key takeaways

ObjectARX belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect ObjectARX to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of ObjectARX from memory before moving on to harder problems.

Reference excerpt

ObjectARX (AutoCAD Runtime eXtension) is an API for customizing and extending AutoCAD. The ObjectARX SDK is published by Autodesk and freely available under license from Autodesk. The ObjectARX SDK consists primarily of C++ headers and libraries that can be used to build Windows DLLs that can be loaded into the AutoCAD process and interact directly with the AutoCAD application. ObjectARX modules use the file extensions .arx and .dbx instead of the more common .dll. ObjectARX is the most powerful of the various AutoCAD APIs, and the most difficult to master. The typical audience for the ObjectARX SDK includes professional programmers working either as commercial application developers or as in-house developers at companies using AutoCAD. New versions of the ObjectARX SDK are released with each new AutoCAD release, and ObjectARX modules built with a specific SDK version are typically limited to running inside the corresponding version of AutoCAD. Recent versions of the ObjectARX SDK include support for the .NET platform by providing managed wrapper classes for native objects and functions. The native classes and libraries that are made available via the ObjectARX API are also used internally by the AutoCAD code. As a result of this tight linkage with AutoCAD itself, the libraries are very compiler specific, and work only with the same compiler that Autodesk uses to build AutoCAD. Historically, this has required ObjectARX developers to use various versions of Microsoft Visual Studio, with different versions of the SDK requiring different versions of Visual Studio. Although ObjectARX is specific to AutoCAD, Open Design Alliance announced in 2008 a new API called DRX (included in their DWGdirect library) that attempts to emulate the ObjectARX API in products like IntelliCAD that use the DWGdirect libraries.

References

See also Autodesk Developer Network Autodesk AutoCAD

Worked examples

Example 1 — a first encounter with ObjectARX

Start with the simplest possible case. Write down what ObjectARX claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to ObjectARX before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about ObjectARX ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of ObjectARX

In research: ObjectARX appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses ObjectARX in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: ObjectARX is common in secondary-school and first-year university syllabi. It links to neighbouring topics Application programming interfaces, Computing stubs, so understanding it makes those chapters shorter.
In everyday life: Look for ObjectARX outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study ObjectARX in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what ObjectARX means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain ObjectARX out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is ObjectARX in simple terms?

ObjectARX (AutoCAD Runtime eXtension) is an API for customizing and extending AutoCAD. The ObjectARX SDK is published by Autodesk and freely available under license from Autodesk.

Why does ObjectARX matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study ObjectARX?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on ObjectARX.