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Tim Holt, a research assistant at Oregon State University and member of "commercial mod group" Transmodrify provided a behind-the-scenes look at how he is integrating mods of Half-Life 2 for two government-funded projects.

Rusel DeMaria, Blogger

November 3, 2005

8 Min Read

Speaking on the first day of the 2005 Serious Games Summit, Tim Holt, a research assistant at Oregon State University and member of "commercial mod group" Transmodrify discussed the plight of independent development and, in particular, those who want to do games for non-entertainment markets, commenting: “We all want to look like a million bucks, but it costs a million bucks to look like a million bucks.” So what, he asked, is the alternative?

Holt, who formerly worked at Valve, suggested that modding is a great way to produce quality content on low budgets. Citing a desire to create games that look like Quake IV or Civilization IV, combined with an interest in exploring the serious games space, he explained that modding, as a concept, is not like traditional development. There are quite a few good game engines available – Half-Life 2, Unreal, Far Cry and Neverwinter Nights, to name a few - that offer an SDK, reusable content, level editing, and reusable scripts of all kinds. According to Holt, mods can extend the life of a game or franchise, and are easily adapted for use in serious games.

Showing the in-game engine utlilizing title screen of Half-Life 2, Holt pointed out how even that screen demonstrated much of what was already supplied in the package – sun glare/lighting effects, people walking and moving about, the telephone wires being moved by the wind, and so forth.

On Modding Using Source

Narrowing his focus, Holt took a brief look at the history of Valve's Hammer editor and how it evolved from an amateur product called Worldcraft, which Valve bought and continued to develop. He suggested using Softimage's XSI to create content for both Half-Life and Unreal mods, without the high pricetag of the full software package - while the free version comes with a few limitations, it is still a great asset for modders.

Speaking on some of the benefits of modding using Half-Life 2 Source Engine, Holt pointed out that the engine had around 5000 hi-res textures, though he admitted that, given the theme of Half-Life 2, most of what you could get was pretty grungy. In a hospital simulation he was working on, Holt commented that he definitely had to clean up the textures. Moreover, there are also about 5000 sounds – however, some of these sound effects include small variations such as 10 different sounds of footsteps on tile, to give variety to the game experience. There are also more than 2000 or so models of characters and objects to use.

In passing, Holt also mentioned how Valve would often hire people they discovered in the modding world, then went on to offer the restrictions that come hand in hand with mods:

  1. You can't make content using the company's engine and assets and then sell it commercially.

  2. You have to own a copy of the game to play the mod.

  3. You can't take content out of one game system, i.e. Half-Life 2, and put it in another, such as Unreal.

But despite these limitations and conditions, modding offers a lot: “It's about reusing the wheel, not reinventing it.”

GNNViz - A virtual forest simulation/exploration environment, currently being developed at Oregon State University with funding from the Federal Joint Fire Science Program.

Seriously, Half-Life 2?

After his overview, Holt went on to talk about the serious game mod projects he'd been working on, starting with an early prototype of medical simulation game project, Pulse!!!, which is funded by Congress via the Office of Naval Research. The project Holt worked on was an early pre-visualization prototype, in advance of a larger development system to be directed by Prof. Claudia Johnston of Texas A&M University-Corpus Christi, to test the issues needed to successfully move nurse training into a full scale 3D game-like environment.

[NOTE: The full version of the simulation, currently in development at BreakAway Games, no longer uses the Half-Life 2 Source Engine as a basis for its development.]

For the doctors in the similation, he used an ordinary civilian model from Half-Life 2, but worked to give it better posture – the civilians in Half-Life 2 were pretty downtrodden and had a definite slouch. Otherwise, with a bit of cleaning up of the skin and textures, the engine was extremely functional for its task, including careful use of the AI scripting and other behavioral code.

Talking about his other serious game mod project, GNN Visualization, a forestry model for the U.S Forest Service through Oregon State University, he mentioned that he modifiied an in-game code routine that randomly covered ground with tufts of grass. The project has taken the Valve Source game engine, and turned it into a multi-user forest data visualization and collaboration tool for forest researchers. But, instead of using grass, he covered the ground with trees for this serious game mod. He also explained that it was simpler to make the characters smaller and slow them down rather than make the tree models bigger.

In an aside, Holt spoke to people who were interested in building their modding experience. “Start modding with simple changes,” he suggested. “And before you actually start modding – play the game. Play it once to learn what it does and what is possible. Then play it again to take an inventory of the game… looking for elements you can use in your application.” He also suggested that people read wikis, mailing lists, and any other resources online for modding. Among his other suggestions were: checking out the Valve wiki, visiting a sites such as moddb.com to learn about what mod engines are available, exploring that game's content from the file level, and using a Windows Explorer-type tool called GCFScape, specifically made to allow browsing and extraction from Steam cache files for Half-Life 2.

Returning to his experience working on his latest projects, he suggested starting with simple modifications such as modding the splash screen. In his medical simulation, Pulse!!, the splash screen had many objects that set the scene – a vital signs monitor, the patient, medical instruments such as forceps, papers on a bulletin board and more. This efficiently set the scene and tone for the simulation.

An early prototype for Pulse!!

And to turn civilians into doctors, he showed how very minimal changes to the code – mostly giving the model a new name – medic – instead of civilian – was all he had to do to have a new character in his game, who would walk through the hospital looking like a doctor. Then he could go further later by adding some specific doctor behaviors, but for now, he had working actors with minimal effort. The same principle worked for changing tufts of grass into trees, with a call to a different graphic within the random routine.


Finishing up, Holt talked about other ideas and challenges he faced in fleshing out these games, such as creating appropriate hand movements for a surgeon using a forceps or a scalpel, which required more specific modeling work. He showed how the standard “radar” map of Half-Life 2 could be modified to work as a sophisticated data display for forest statistics, showing who owns a section of the map or other available data. He also talked about linking to existing simulations or data – using external sims instead of trying to code a whole new sim within the mod. Another idea was to create a real-time component for the medical game in which patients, if not attended to periodically might get worse or even die, sort of a medical simulation in a Tamagotchi style.

Holt also suggested a few other mods to look up as a parting gift, such as Garry's Mod, which explores Half-Life 2's capabilities as a sandbox to play around in, and the machinima piece 'A Few Good G-Men', an excellent example of high quality output from the Half-Life 2 engine. All in all, this was a helpful basic talk that discussed the advantages of using mods to create serious games.


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About the Author(s)

Rusel DeMaria


Rusel DeMaria has been a participant and observer in the electronic gaming industry since its inception. He has written nearly 60 strategy guides and is acknowledged as one of the pioneers of that book genre. DeMaria has been a senior editor and columnist for several national magazines, a speaker at the prestigious Computer Game Developer’s Conference as well as other industry events.

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