Lightmaps In Doom 3 Engine: A Hybrid Approach To Real-time Lighting

[Tels]

I have some ideas for simulating a radiosity with dynamic lights.. probably hard to implement with scripting, also very restricted and difficult for the mapper, but in some key areas it might make a difference.

 

You mean like we already implemented it?

 

See the setting "ambient_light_dynamic" here:

 

http://wiki.thedarkmod.com/index.php?title=Ambient_Sounds%2C_a_zone_approach#Ambient_light_settings

 

Edit: Just wrote an overview article here: http://wiki.thedarkmod.com/index.php?title=Radiosity (so it can be found if someone searches for radiosity)

[STiFU]

Uhm, well!! Your heat-related description of Radiosity is absolutely correct, so I don't understand how you think that the dynamic ambient light method is in any way similar to Radiosity... It works just the same way for computergraphics as for heat: You subdivide surfaces and solve the linear system of equations. So it would be a little too far fetched to say TDM has Radiosity and it's definitely a flame-war-target.

 

Radiosity also isn't calculated from point-lightsources, but just from luminous surfaces, so that's another point not matching up with dynamic ambient. Global Illumination methods on the contrary use actual lightsources for the calculations, so that would be at least one step closer.

 

Let's see, what term does describe this technique better? It's somewhat similar to the dynamic contrast setting of many monitors, with the enhancement of colorchange:

 

"Local Lightsources' Colorintensity-dependent Dynamic Ambient Lighting" or short: LICDAL!!!

[Tels]

Uhm, well!! Your heat-related description of Radiosity is absolutely correct, so I don't understand how you think that the dynamic ambient light method is in any way similar to Radiosity... It works just the same way for computergraphics as for heat: You subdivide surfaces and solve the linear system of equations. So it would be a little too far fetched to say TDM has Radiosity and it's definitely a flame-war-target.

 

It is definitely not radiosity (or at least it is so simple that one wouldn't call it that). But it runs in real-time and automatic, and thats better than anything else (because they are not implemented at all

 

 

Radiosity also isn't calculated from point-lightsources, but just from luminous surfaces, so that's another point not matching up with dynamic ambient.

 

Erm guess where the light on the liminous surface comes from - you guess it, from a light source Of course simulating how the light gets reflected from a surface and injecting that back into the scene is way better, but we have to start somewhere.

 

Global Illumination methods on the contrary use actual lightsources for the calculations, so that would be at least one step closer.

 

Let's see, what term does describe this technique better? It's somewhat similar to the dynamic contrast setting of many monitors, with the enhancement of colorchange:

 

"Local Lightsources' Colorintensity-dependent Dynamic Ambient Lighting" or short: LICDAL!!!

 

Well, I won't stop you implementing radiosity, but even if you can manage this in real-time, a lot of people will complain because they don't have the latest, greatest hardware. And I fail to see how radiosity would improve the gameplay or the "beautyfullnes" of the game. Yes, it will be more realistic, but its very expensive.

[STiFU]

Erm guess where the light on the liminous surface comes from - you guess it, from a light source

To be precise, in the basic radiosity calculations only the self-radiation of surfaces is taken into account, but not actual lightsource. However, you can derive the self-radiation of the surfaces from the present lightsources in a preprocessing pass, e.g. raytracing or a the normal render pipeline of real-time engines.

 

Well, I won't stop you implementing radiosity, but even if you can manage this in real-time, a lot of people will complain because they don't have the latest, greatest hardware. And I fail to see how radiosity would improve the gameplay or the "beautyfullnes" of the game. Yes, it will be more realistic, but its very expensive.

Radiosity would wildly improve the visual appearance of TDM!! Have a look at Mirror's Edge for example, which uses baked Global Illumination (even better than Radiosity). It simply looks awesome. The Doom engine has always been criticized because of its pure dynamic lighting approach and the resulting missing Radiosity or Global Illumination pass, which is why I dream about an implementation of Lightmap support once Doom 3 has gone open source. A realtime implementation of Radiosity or GIs is simply not possible with the modern hardware, besides maybe supercomputers... The closest you can get to this effect in real-time is Screen Space Ambient Occlusion, but even that is highly hardware intensive!

 

Anyway, I wasn't suggesting you should throw the dynamic ambient light feature away. It already poses a great improvement over the default Doom lighting. I like it! But explaining it in a wiki-article together with Radiosity is simply misleading...

[Tels]

To be precise, in the basic radiosity calculations only the self-radiation of surfaces is taken into account, but not actual lightsource. However, you can derive the self-radiation of the surfaces from the present lightsources in a preprocessing pass, e.g. raytracing or a the normal render pipeline of real-time engines.

 

Radiosity would wildly improve the visual appearance of TDM!! Have a look at Mirror's Edge for example, which uses baked Global Illumination (even better than Radiosity). It simply looks awesome. The Doom engine has always been criticized because of its pure dynamic lighting approach and the resulting missing Radiosity or Global Illumination pass, which is why I dream about an implementation of Lightmap support once Doom 3 has gone open source. A realtime implementation of Radiosity or GIs is simply not possible with the modern hardware, besides maybe supercomputers... The closest you can get to this effect in real-time is Screen Space Ambient Occlusion, but even that is highly hardware intensive!

 

Well, I can see how it would improve things if we could get rid of the manually placed dirt decals and still get the same effect (e.g. darker corners, lighter wall across the windows etc).

 

Anyway, I wasn't suggesting you should throw the dynamic ambient light feature away. It already poses a great improvement over the default Doom lighting. I like it! But explaining it in a wiki-article together with Radiosity is simply misleading...

 

Ah ok, could you please fix the article then, as you know alot more about this then me? Maybe write an introduction to the different terms (AO, radiosity etc) and then just link to our poor-mans-thingywhatever?

[STiFU]

Yeah, I can do that... eventually! Exam on Monday. Maybe after that.

[Diego]

You mean like we already implemented it?

 

Cool! Didn't know about that!

 

I was thinking something completely different, though (and with a different purpose). Basic idea: Consider some special lights placed in a strategical position, a dummy volume (close to this light) detects how much light is incident on it and controls this special light to increase it's intensity.

 

It's complicated and not incredibly useful, but I like the mental exercise I could see this used to lit up a room that has absolutely no light in it, but when the player opens a door to a lit room, the dark room will get some 'clarity' besides the direct light.

[Tels]

Cool! Didn't know about that!

 

I was thinking something completely different, though (and with a different purpose). Basic idea: Consider some special lights placed in a strategical position, a dummy volume (close to this light) detects how much light is incident on it and controls this special light to increase it's intensity.

 

It's complicated and not incredibly useful, but I like the mental exercise I could see this used to lit up a room that has absolutely no light in it, but when the player opens a door to a lit room, the dark room will get some 'clarity' besides the direct light.

 

Yeah, that sounds like an improvement to the dynamic ambient light. But I am not sure if we can detect the incoming light on a volume. (And would the mapper need to place the volumen manually?)

[AluminumHaste]

I'm still dreaming of the day where can get this in real time:

 

 

EDIT: OMG!!!! http://www.youtube.com/watch?v=ACbdCrGbISo

[rich_is_bored]

That video isn't real-time rendering. Here's some real-time radiosity for you...

 

 

And another better example...

 

Edited March 15, 2010 by rich_is_bored

[STiFU]

Phew, that's some sweet stuff!!

[AluminumHaste]

That video isn't real-time rendering. Here's some real-time radiosity for you...

 

 

And another better example...

 

 

Thanks for stopping in Rich! I was always thankful for your advice and guidance on the Doom3World forums, glad to see you here. Thanks for the vids, I have to change my pants now!