By mid June 2010 I worked on a personal project that consisted in rendering models from the classic Quake 2 game by Id Software. Here’s a video of the renderer.

Quake 2 was one of my favorite games when I was young and researching how to load and render its 3D models instantly sent me down the nostalgia path.

For those who might be interested in developing their own loader, Quake 2 models are very easy to read and parse from languages such as C and C++. This is mostly because .md2 files consist in a binary file format that we can easily read into C structs.

David Henry does a great job at explaining how the bytes are stored internally, so I’m not going to reproduce his work here. Nonetheless, here’s the md2 file header:

struct md2_header
{
     int id;
     int version;

     int skinwidth;
     int skinheight;

     int framesize;

     int numskins;
     int numvertices;
     int numtexcoords;
     int numtriangles;
     int numglcmds;
     int numframes;

     int skinDataOffset;
     int textureDataOffset;
     int triangleDataOffset;
     int frameDataOffset;
     int glcmdsDataOffset;
     int endOffset;
 };

Quake 2 model files organize vertices and triangles into keyframes: a series of poses that enable us to draw the model animated. The texture to use when rendering the model is referenced by the file too. Each file might point to zero or more textures in the PCX format. Textures are called the model’s “skin” in Quake 2′s terminology.

The video above were generated using the custom renderer that I wrote. It is using OpenGL and GLUT to create the window and draw the model.

Now, you’ve probably noticed that the animation in the video above looks rather “choppy”. It’s definitely not smooth. The reason is that keyframes provide a base for animating the model, but not enough frames are provided as to produce a “continuous” animation.

In my next post I’m going to show you how we can improve this situation. Stay tuned!

For the past month and a half I’ve been working on and off on a project that consists in the development of a custom Quake 2 BSP map renderer. The renderer was written from scratch using nothing but C++ and OpenGL 2.0.

Click on the image for more screenshots.

The project’s objective was twofold: to help develop the foundation for a custom object-oriented rendering engine and to test my skills at what seemed as such a daunting task as loading, rendering and navigating Quake 2 maps in realtime.

There is a lot of information on the Internet regarding Id Software’s BSP file format and the way polygons, texture data, lightmaps and any other aspects of the game are stored. In my experience, no website provides “the whole picture”, so if you’re planning on rolling your own renderer, be prepared to spend as much time doing research online and developing and testing ideas as writing code.

At its current status, I consider the renderer to be in a pretty good state, where it supports loading maps directly from Quake 2′s original PAK files, rendering its polygons, performing texture mapping, applying lightmaps, adding a skybox and leveraging the map’s visibility information to prevent large amounts of non-visible geometry from being sent to the Video Card. I’m glad I’ve been able to approximate the game’s look and feel in what I consider very close to the original.

There are still many open points that could be addressed, such as experimenting with blur effects to increase the sky’s realism and bring life into the skybox. All texture mapping and lighting is currently done using shaders, so the basic foundation for post production visual effects is laid and ready to be built upon.

At some point, I might provide executable versions of the renderer so you can try it yourself. In the mean time, if you’d like to view other rendered images, I’ve added more screenshots from this project at the Projects page of this site.

Here’s also a YouTube video showing an actual run of the Renderer: