Source engine rendering in... UDK ?

Yeah, the HL2 and source materials are pretty beastly.

I don't see any reason why you couldn't get a similar lighting setup in the UDK, or any engine for that matter. The big difference I think isn't so much the lighting but the materials. Source games such as HL2 are extremely diffuse driven, where the obviousness of a normal map is extremely subtle. Compare that to games made with UE3, which are very normal and specular driven, you get that overly glossy/shinny/wet look.

Comes down to how you model, texture and light stuff really. I mean the look source has is quite unique to that engine but quite a few unreal games get away from the UT style that is sort of the default. Though I am sure there is a lot of custom code involved in some cases too.

Source also makes heavy use of brush work in its final levels where as unreal is much more mesh focused.

The key is understanding that the approach of the Epic artists is to make you think "OMFG HOW GRAPHICS IN GAMES WHUUU" while the approach of the Valve's artists is to make you think "oh I am now in a forest, oh I am now in a sewer." Like said by others the most obvious difference is more subtle specular and normal maps. However, that's not all! Textures tend to be lower resolution with details only where needed. This isn't just because of engine power, but also because having alot of detail is, in the end, UNrealistic because your eye filters most details out and having them on the screen just overwhelms your brain and (for me at least) makes your eyeballs itch. Another reason staring at screenshots is not a good way to judge the look of a scene

Unfortuantely I don't think you'll be able to get the look at all in Unreal simply because Unreal's lighting model is, well, shitty. Tons of complex shaders, but the actual basic function of LIGHT just isn't implemented as well. At least, that's how it used to be, I don't know anything about this new lightmass business, but IIRC in the past unreal didn't support radiosity, GI, or final gathering, all of which the source engine uses while it's "being old and slow and outdated compiling lighting." So that brings up another point, don't use dynamic lights or heavy post process. Post process should generally be confined to levels and mild HSV used only to FIX oversaturation in particular color ranges

First of all, you can emulate the same image in basically every engine.

Now, especially with Unreal's Lightmass it gets easier to achieve lighting similar to Half-Life 2, as it does Radiosity and Prebaked Lighting in the same way the Valve Rad tools do. If you put the Half-Life 2 Materials into UDK (load the textures into a package, recreate the Material Setups in Unreal's material editor) and adjust the values accordingly it will look the same (given that you are not using fancy Postprocessing or weird lighting).

Obviously when it comes to props and geometry Half-Life 2 also doesn't have bevels on everything, which makes it look more lowpoly but on the other hand avoids the Gamey look of round edges which all of Epics games have and looks more defined in stead.

I find it generally quicker to achieve good results in Source because the vrad tool is pretty simple. Just set the sky and shadows color and the intensity of the light_environment and you are go. Now on Unreal you need to play with hundreds of variables until you are satisfied with the results. I remember spending at least 2 full weeks only tweaking the lightmass settings in my Sci-Fi scene (the interior one) until I got the result that I wanted

So basically stay away from exaggeration:

- Post process (unless used subtly) is a big no-no

- Keep high-frequency noise in your normal maps minimal

- Use glossiness maps to define your specular maps better

- Tone down SSAO until it's pretty subtle (like 0.3 or so)

- You can also add a postproccess chain to access the default postproccess values and crank up saturation a little bit. By default all UDK maps are desaturated by 20% if I recall correctly.

Another great feature in Source that you will never get in Unreal is the cubemaps thing. In Unreal you need to assign a cubemap to each material, so unless you create multiple instances of the same material you are restrained to only one cubemap for material. Just take a look at a game like Mass Effect, the cubemaps are pretty simple and generic!

I also could never get the HDR tone mapper to work in Unreal like it does in Source. Does anyone know if that's possible?

Wait, all UDK levels are desaturated by default? Can anyone confirm that? Can it be fixed in a script file or do you have to account for it on a per map basis?

Quote from e-freak

Now, especially with Unreal's Lightmass it gets easier to achieve lighting similar to Half-Life 2, as it does Radiosity and Prebaked Lighting in the same way the Valve Rad tools do.

That's awesome! My reasons for standing my source are slowly slipping away

Unreal uses a level wide Postprocessing and can add additional Post Processing triggered in areas or over certain events. One important step in getting away from "teh unreal looks" is by using Postprocessing as you want and need it and not just leave the default values enabled. It's simmilar to every Source Map looking the same because everyone uses City17 assets, many Unreal levels look alike just because of the default Postprocessing (random DOF, Desaturation, Bloominess, etc.).

I'm not exactly sure why but Lightmass just looks a lot more appealing to my eyes then the radiosity in Source.