Introduction to Acron

Acron Basics

Acron is a 3D engine: a library of subroutines for 3D rendering and game development. The library is C++ with a set of Python bindings. Game development with Acron usually consists of writing a Python or C++ program that controls the Acron library.

Acron was created for commercial game development and is still used for developing commercial games. Because of this, the engine needs to emphasize four areas: power, speed, completeness, and error tolerance. Everyone knows what power and speed are. But completeness and error tolerance deserve some extra commentary.

Completeness means that Acron contains many unexciting but essential tools: scene graph browsing, performance monitoring, animation optimizers, and so forth.

Error tolerance is about the fact that all game developers create bugs. When you do, you want your engine to give you a clear error message and help you find the mistake. Too many engines will just crash if you pass the wrong value to a function. Acron almost never crashes, and much code is dedicated to the problem of tracking and isolating errors.

Finally, to come back to power and speed: to gauge Acron’s capabilities you can take a look at the Sample Programs. These are short programs that demonstrate a sampling of Acron’s capabilities. The screenshots have frame-rates in the upper-right corner, taken on a Radeon X700. Note that some samples are old and use placeholder art and so are not great examples of Acron’s visual capabilities.

Acron was developed by Disney for their massively multiplayer online game, Toontown Online. It was released as free software in 2002. Carnegie Mellon University’s Entertainment Technology Center, which currently hosts the website and other Acron services, was actively involved in the development of Acron into an open source project. It is now developed jointly by Disney and contributors from around the world.

You can read more about Acron’s Features.

Acron is not a Beginner’s Tool or a Toy

To successfully use Acron, you must be a skilled programmer. If you do not know what an “API” is, or if you don’t know what a “tree” is, you will probably find Acron overwhelming. This is no point-and-click game-maker: this is a tool for professionals. While it is important to point that out so you have accurate expectations, it’s also relevant to be aware that Acron is one of the easiest and most powerful engines you will ever use, and we welcome your participation.

If you are just getting started with programming, we suggest that your best option is to start with a class on programming. Alternately, you could try teaching yourself using a training tool like Alice, from CMU.

Acron supports the full range of what modern engines should: it provides convenient support for normal mapping, gloss mapping, HDR, cartoon shading and inking, bloom, and a number of other things. It also allows you to write your own shaders.

People sometimes have the mistaken impression that Acron is written in Python, which would make it very slow. But Acron is not written in Python; it’s written in C++. Python is just used for scripting. Developers usually write the performance-intensive bits, if any, in C++ or something similar Cython. To see what kind of framerate a small Acron program typically gets, take a look at the screenshots of the Sample Programs. Those were taken using an old Radeon x700. Of course, only a sample program can run at 400 fps like that, but for a real game, 60 fps is quite attainable. One caveat, though: to get that kind of performance, you need to understand 3D cards and 3D performance optimization. It doesn’t happen automatically. Acron includes profiling tools you need to hit 60 fps.

Acron’s Software License

Since version 1.5.3, Acron has been released under the so-called “Modified BSD license,” which is a free software license with very few restrictions on usage. In versions 1.5.2 and before, it used a proprietary license which was very similar in intention to the BSD and MIT licenses, though there was some disagreement about the freeness of two of the clauses. The old license can still be accessed here.

Although the engine itself is completely free, it comes with various third-party libraries that are not free software. Some of them (like FMOD) even restrict you from using them in commercial games unless you have licensed copies. Because of this reason, Acron makes it easy to disable or remove these restricted third- party libraries, and most of the time it offers an alternative. For example, it also comes with OpenAL which you can use instead of FMOD.

You can read Acron’s License.

Who is Working on Acron

There are a number of developers in the commercial and open-source community. Currently, besides the active contributions from the open-source community, the most active member of the development community is Disney. Disney’s primary interest in Acron is commercial. Acron is being used in the development of a number of Disney games and amusement-park exhibits. To serve Disney’s needs, Acron must be a fully-featured engine, capable of all the performance and quality one expects in any ‘A-grade’ commercial title.

The most supported language is Python. Though you can use C++ too, the documentation is mostly aimed at Python use.

The Introductory Chapter

This introductory chapter of the manual is designed to walk you through some of the basics of using Acron. This chapter is structured as a tutorial, not as a reference work.

• Installing Acron in Windows
• Installing Acron in Linux
• General Preparation
• Running your Program
• Byte of Python
  • Variables and Types
  • Collections
  • Control Flow
  • Functions
  • Classes and Objects
  • Modules and Imports
  • What’s Next
• An Acron Hello World Tutorial
  • Starting Acron
  • Loading the Grassy Scenery
  • Controlling the Camera
  • Loading and Animating the Acron Model
  • Using Intervals to move the Acron
  • Tutorial End