Panda3D

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Panda3D
Latest release 1.5.2 / May 2008
Preview release 1.5.3 (TBA)
OS Microsoft Windows, Linux, Mac OS X
Genre Game Engine
License Panda3D License
Website http://panda3d.org/

Panda3D is a game engine: a library of subroutines for 3D rendering and game development. It includes graphics, audio, I/O, collision detection, and other abilities relevant to the creation of 3D games.[1]

Panda3D is open source and free of charge, but unfortunately, certain errors in the design of the license keep it from attaining the status of truly Free Software. Even so, Panda3D can be used for both free and commercial game development at no financial cost.

Panda3D's intended game-development language is Python. Although the engine itself is written in C++, it utilizes an automatic wrapper-generator to expose the complete functionality of the engine to the Python user. It also integrates with Python's garbage collector: engine structures are usually automatically managed. The manual and the sample programs use Python. Though, since the engine is written in C++, it is also callable from C++ code. It is not uncommon that developers choose to use Panda3D with C++ instead of python.

The users of Panda3D include several large commercial games, a few open source projects, and a number of university courses that leverage Panda3D's short learning curve. The community is small but active, questions on the forum are generally answered within an hour.

Contents

[edit] Design

Panda3D is a scene graph engine.[2] This means that the virtual world is initially an empty cartesian space into which the game programmer inserts 3D models. Panda3D does not distinguish between "large" 3D models, such as the model of an entire dungeon or island, and "small" 3D models, such as a model of a table or a sword. Both large and small models are created using a standard modeling programs such as Max or Maya, loaded into Panda3D, and then inserted into the cartesian space.

The Panda3D scene graph exposes the functionality of OpenGL and DirectX in a fairly literal form. For instance, OpenGL and DirectX both have fog capabilities. To enable fog in Panda3D, one simply stores the fog parameters on a node in the scene graph. The fog parameters exactly match the parameters of the equivalent calls in the underlying APIs. In this way, Panda3D can be seen as a thin wrapper around the lower-level APIs. Where it differs from them is that it stores the scene, whereas OpenGL and DirectX do not. Of course, it also provides higher-level operators, such as loading models, executing animations, detecting collisions, and the like.

Panda3D was first engineered before the existence of vertex and pixel shaders. It acquired support for manually-written shaders in 2005. However, users have been slow to leverage modern per-pixel lighting techniques in their games. The developers theorize that this is because shader programming can be quite difficult, and that many game developers want the engine to handle it automatically.

To remedy this situation, the Panda3D developers have recently given Panda3D the ability to synthesize shaders automatically. This synthesis occurs if the 3D modeler marks a model for per-pixel lighting, or if the modeler applies a normal map, gloss map, self-illumination map, or other capability that exceeds the capabilities of the fixed-function pipeline.[3] The intent of the synthesis is to render the model as the modeler intended, without any intervention from the programmer.

Currently, the engine supports most modern per-pixel lighting techniques, with one glaring omission: dynamic shadows. Although it is possible to implement dynamic shadows using Panda3D by writing the necessary shaders oneself, it is not easy to do. The developers recognize this as a serious limitation and plan to expand the shader generator's capabilities to incorporate this feature in the next year or so.

[edit] Non-Graphical Capabilities

Panda3D provides capabilities other than 3D rendering. Chief among these are:

  • Performance analysis tools.
  • Scene graph exploration tools.
  • Debugging tools.
  • A complete art export/import pipeline.
  • 3D Audio, utilizing either FMOD or OpenAL.
  • Collision detection.
  • Physics system, and full integration for the Open Dynamics Engine.
  • Keyboard and Mouse support.
  • Support for unusual I/O devices.
  • Finite state machines.

[edit] History

The Disney VR studio is a branch of Disney that was created to build 3D attractions for Disney theme parks. They built an attraction called "Aladdin's Magic Carpet," and the engine they created for that was eventually to become Panda3D. The engine in its current form bears little resemblance to those early years. Over time, Panda3D was used for additional VR rides at Disney theme parks, and was eventually used in the creation of Toontown, an online game set in a cartoon world. [4]

In 2002, the engine was released as open source. According to the authors, this was so that they "could more easily work with universities on Virtual Reality research projects." [5] However, it took some time for Panda3D to take off as an open-source project. From the article:

The system, although quite usable by the team that developed it, was not quite "open source ready." There were several interested users, but building and installing the system was incredibly complex, and there was little in the way of documentation or sample code, so there was no significant open source community right away.

However, the open-sourcing of the engine allowed Carnegie Mellon's Entertainment Technology Center to join in the development of the engine. While Disney engineers continued to do the bulk of the development, the Carnegie-Mellon team built a role for itself polishing the engine for public consumption, writing documentation, and adding certain high-end features such as shaders.

Panda3D's name was once an acronym: "Platform Agnostic Networked Display Architecture." However, since that phrase has largely lost its meaning, the word "Panda3D" is rarely thought of as an acronym any more.

[edit] Software License

In 2002, when the engine was open sourced, the goal of the developers was to create a Free Software license. However, certain mistakes were made, and the resulting license is not Free Software. The following is the rights-granting portion of the license:

Licensor hereby grants to any person obtaining a copy of the Software a nonexclusive license to use, copy, modify, merge, publish, distribute, and/or sublicense copies of the Software, and to permit persons to whom the Software is furnished to do so, on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. [6]

This clause is typical of a Free Software license. Among other things, it allows the creation of free games and commercial games at no charge. Most of the license is fairly typical Free Software boilerplate. However, there are two clauses in the license that are not free. The first of these is:

An electronic copy of the source code for major modifications that You make to the Software should be forwarded to Licensor at Panda.Project@Disney.com...

This clause arguably requires you to give any modifications you make back to Disney. This is not allowed in a Free Software license: a true Free Software license allows you to keep modifications to yourself. The second clause that is not Free Software compatible is as follows:

The Software may not be downloaded or otherwise exported or reexported into (or to a national or resident of) Cuba, Libya, North Korea, Iran, Syria, or any other country to which the U.S. has embargoed goods...

The intent of this clause was merely to avoid liability by complying with US export law. However, this was a mistake. A Free Software license may not discriminate against Cubans, Libyans, and so forth. Even if the law discriminates, the license is not allowed to be a party to that discrimination or to fuel it.

In addition, Panda3D makes use of several third party libraries whose licenses are also not Free Software, including FMOD, FFTW, and ARToolKit. The developers have admitted these shortcomings and are in the process of changing the particularly onerous terms of the license to meet the requirements of Free Software.

[edit] Users

Here is a partial list of companies and commercial products that utilize Panda3D:

Here is an incomplete list of free software projects building on Panda3D:

[edit] References

  1. ^ Panda3D Manual.
  2. ^ Panda3D Manual Chapter: 'The Scene Graph'.
  3. ^ Panda3D Manual Chapter: 'The Shader Generator'.
  4. ^ Gamasutra Postmortem: Disney's Toontown (discusses history of Panda3D).
  5. ^ Proceedings, PyCon 2004: The Panda3D Engine - Python Scripting for Game and Simulation Development.
  6. ^ Panda3D License, Official Site..

[edit] External links

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