1. Info
The Rad-Therapy II project is similar to its HL1 counter-part Rad-Therapy. It is in early stages of development. It serves as a proof-of-concept and as a testbed for Nuclide its compatibility with Source Engine entities. This project produces a freely available, multi-platform QuakeC-based HL2 SDK replacement.
This is made possible with the FTE QuakeWorld engine and its HL2 model file format plugin, as well as the Open Dynamics Engine for physics.
2. Downloads
If you already have FTE QuakeWorld for your platform:
Latest release (03-22-2024),
save it into Half-Life 2/hl2/
3. Screenshots
This image was created for use on this site using components taken from Half-Life 2 owned by Valve Corporation. The copyright for the components are held by Valve Corporation while the copyright for these particular compositions are held by us.
4. Installation
Extract the release archive, merge the contents of the folder inside the tarball with your Half-Life 2 installation.
You can then proceed to run the game with the RadTherapy2 script.
The engine should also automatically detect HL2 when placed within the game directory, however you may need to pass -halflife2 just in case you have one massive directory with multiple FTE-supported games in it.
You can also launch mods like this: fteqw.exe -halflife2 -game gmod9
5. Building
Be familar with the git program, and you can clone Nuclide, and then
within that directory clone the repo.
Then issue: make game GAME=hl2
to build the various pieces of game logic (in the form of QuakeC .dat files).
6. Credits
- Spike for FTEQW and for being the most helpful person all around!
- Xylemon for the hundreds of test maps, verifying entity and game-logic behaviour
- To my supporters on Patreon, who are always eager to follow what I do.
- Any and all people trying it, tinkering with it etc. :)
7. License
ISC License
Copyright (c) 2018-2026 Marco "eukara" Cawthorne
Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
8. FAQ
Players may want to try a different multiplayer experience, with more flexibility and features than the aging Source Engine.
The HL2 Source Engine is also not freely available for license, and projects out there may be looking for a way to migrate their mod into a standalone game. This project already gives them a basis for their port.
- Rad-Therapy II is not HL2 and is not intended to 'replace' HL2.
- Be able to play the game in multiplayer. Until FTEQW supports more of the model format fully, we can aim for singleplayer support in the future.
- It should also be compatible with whatever free or libre replacement data will become available in the future.
- It's not a port of existing sources, and is not compatible with mods unless they too are rebuilt.
- It meant to be used to build other games and projects, similar to what HL2 is.
It is all free. The binary releases are free, the sources are free. All parts of Rad-Therapy II have reasonable copyright terms permitting free redistribution. You can do whatever you wish, including building a game with it and sell it on the Internet or in the real world. We only ask for attribution.
However you currently still need to supply the data files for Half-Life 2 in order to really play this. That game is still under Copyright © Valve Corporation. You can find ways to purchase the game both physical and digital on frag-net.com.
The developer is doing this for everyones benefit, even small contributions help in making a big difference.
Being built from the ground up with hindsight and other modifications in mind, it's a lot simpler to get started creating custom objects. You can design whole weapons, items, monsters (as well as their schedules) without writing a single line of code. This is due to Nuclide's data oriented design and the use of id Tech 4 style decl files.
Because it's built on Nuclide, it also has a different netcode, with weapon prediction standard across the board. There's also bots included with every game, as well as voting features and a metamod inspired plugin system, with a few ports of popular plugins.
Even gamerules can be swapped out on a whim, as they're simply external modules separated from the server to begin with.
Anything that the engine binary (provided by FTE QuakeWorld) runs on is supported. All components in Rad-Therapy II are platform/architecture independent. Being a QuakeC project has that benefit. This generally means that unless you are making engine modifications for your project, you will not need to port your project.
We've successfully tested it ourselves on Linux, OpenBSD, and Windows.
It is mainly orchestrated by Marco Cawthorne which you can support on their Patreon. He also runs the frag-net game network that powers the on-line backbone of the project. Helping out with the costs that way is greatly appreciated. That said, expressing yourself in the Matrix chat can also nudge the project. If you're the type of person that knows exactly what we need and can lend a hand, be sure to reach out!
Rad-Therapy II logo by Vera Visions L.L.C.;
This site Copyright © 2025, 2026 Rad-Therapy II Project; FTE QuakeWorld is Copyright © 2002-2026 David Walton; Half-Life, and any associated characters belong to Valve Corporation. All Rights Reserved.
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