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DOOM III In Daylight?

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Hi, I was just wondering...would DOOM III look as realistic in a daylight type of environment as opposed to dark sci-fi cooridors? Or was DOOM III''s graphics engine designed to look good only in dark sci-fi cooridors? Thanx, Ciph

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I think they have some daylight scenes. For daylight they probably just add an ambient term to brighten the entire scene.

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download the trailer (it''s now EVERYWHERE on the internet and on every cover CD known to man) and look at the starting bit when the elevator is going up the side of the mountain and judge for yourself.

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I think that cranking up the ambient lighting would look poor, in contrast to the hard shadows and crisp lighting elsewhere.

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they bether use one very big pointlight for the sun:D

(big point.. hehe:D you know what i mean.. big attentuation radius:D)

"take a look around" - limp bizkit
www.google.com

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Guest Anonymous Poster
The sun is usually represented as an infinite directional light with an additional ambient term.

A point light really isn''t suitable, because you''d see objects shadows heading off at incorrect angles.

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if its far enough away it shouldn''t be an issue.. (espencially for small outscenes, like i guess are more regular in doom3 than full landscapes for example)..

does doom3 support directional lights? haven''t seen any yet..:D

"take a look around" - limp bizkit
www.google.com

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haha, yeah, supporting direction lights in such an engine is just extra hassle when all you need to do is stick a point light at some large distance away

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Guest Anonymous Poster
Supporting directional lights is no particular hassle, don''t know why they wouldn''t support ''em - it''s a drop in the bucket of an engine that size.

It''s also a performance win over a faked version with a point light - the lighting math is cheaper with a directional light, you don''t need to provide the same caps on shadow volumes, etc.

I''d be surprised if Mr. ''Master of Optimization'' Carmack left ''em out.

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Yes, you do need to do the same "caps on stencil shadows" - no differing lighting model will help you if you''re inside the shadow volume. In fact, supporting direction lights can be a pain in the arse (excuse my French) - I support both but it''s just a pain maintaining both when our artists use nothing but point lights.

For reference, take this engine: http://www.4drulers.com/ . Same type as DOOM3 (ala less advanced) and they only support point lights.

And there''s really no big performance win at all considering you''re after 25fps in one scene with 6 lights, and 28fps in the scene that has 5 point lights and 1 directional.

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Sorry, forgot to mention the renderpath issues. Imagine several layers of abstraction where implementation of light types differ, starting at the bottom:

* Pixel shader math.
* Vertex shader shadow volume extrusion code.
* Shadow volume capping decision code (the light-eye frustum).
* Higher level shader calling code (odd terminology). Do I use multi-pass attenuation and point, single pass 1.4, or just single pass direction?
* And the hardest part, light attachment logic in your scene graph. If you have a portal-based world, testing to see if a light can see objects it needs to attach to through portals is one code path. Testing with directional lights is another method.

It doesn''t boil down to speed increase or time spent implementing it. It boils down to maintainence time and code complexity when balanced with the usefulness it can achieve, which as I have seen is pretty minimal if the artists never use it!

The bottom-line is, you have correct observations but the benefits are not worth the effort.

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quote:
Yes, you do need to do the same "caps on stencil shadows" - no differing lighting model will help you if you''re inside the shadow volume.


You don''t strictly need a back cap, since the shadow volume converges to a single point at infinity, see <A HREF="http://www.gamedev.net/columns/hardcore/shadowvolume/page3.asp">http://www.gamedev.net/columns/hardcore/shadowvolume/page3.asp</A>

quote:
In fact, supporting direction lights can be a pain in the arse (excuse my French) - I support both but it''s just a pain maintaining both when our artists use nothing but point lights.


I support both as well. I don''t find it to be any particular burden. Compared to a lot of stuff in the engine, one extra type of light is pretty minimal.

quote:
And there''s really no big performance win at all considering you''re after 25fps in one scene with 6 lights, and 28fps in the scene that has 5 point lights and 1 directional.


Big is open to interpretation. I''d consider the 12% frametime difference that represents ''big.''

quote:
It doesn''t boil down to speed increase or time spent implementing it. It boils down to maintainence time and code complexity when balanced with the usefulness it can achieve, which as I have seen is pretty minimal if the artists never use it!


In an outdoor game, there should always be at least one directional light. I know doom 3 is an indoor game, but the id intends to license this engine. They''d do well to support people who want to produce outdoor games.

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quote:
Original post by Anonymous Poster
They''d do well to support people who want to produce outdoor games.


Why? The companies that license the engine can put it in if they want...


You have to remember that you''re unique, just like everybody else.

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quote:
Original post by python_regious

Why? The companies that license the engine can put it in if they want...



Because they''d license an engine that does support them to save them the time. You not build the whole engine themselves? The whole point of licensing an engine is that adding features is minimal. They''d already have their work cut out adding a scenegraph to hold an outdoor scene efficiently.

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quote:

You don''t strictly need a back cap, since the shadow volume converges to a single point at infinity



Yep. Good point. But it only enforces the idea that it''s another special case - this is a speed issue, it has nothing to do with maintainence as the capping code still needs to be written.

quote:

Big is open to interpretation. I''d consider the 12% frametime difference that represents ''big.''



We''re talking possibly 2 rooms out of a 30 room game here. Simply not worth it when you can get away with a point light. Remember Abrash''s old Quake articles on stable framerates as opposed to one frame rate in the entire level except where it spikes and runs fluid as silk in one small part of the level? Same thing... again, framerate is not an issue.

quote:

In an outdoor game, there should always be at least one directional light. I know doom 3 is an indoor game, but the id intends to license this engine. They''d do well to support people who want to produce outdoor games.



Yes, another good point. But then, that''s assuming id *wants* to support outdoor games. I''m not going to assume either way.

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actually, outdoor lights are not that well faked with a simple directional light.. there is need for other techniques for outdoor lighting..

"take a look around" - limp bizkit
www.google.com

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quote:
Original post by davepermen
actually, outdoor lights are not that well faked with a simple directional light.. there is need for other techniques for outdoor lighting..


Point lights don''t do all that well for indoor lighting either. If you want to have unified shading code in realtime, though, you ain''t gonna be able to use global illumination.

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sure.

but doom3 scenes are dark scenes, there, mainly the direct illumination does mather. something normally never mattering in outdoor scenes. it matters much more normally in indoor scenes.

not that indirect lighting doesn''t mather much in indoor:D but in outdoor, direct lighting doesn''t mather much.

"take a look around" - limp bizkit
www.google.com

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A simple thing you can do for outdoor scenes is:

Directional Bumpmapping + ShadowMap (sunlight) +
Skylight (bumped cubic lookup or interpolation between sky/ground color based on per-pixel normal)

The skylight gives you some ambient with color variance based on the per-pixel normals so you get lighting variation even if the sunlight is weak or in shadow and you can always see the bumpmapping effect.

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quote:
Original post by neurokaotix
This is why I think that HL2''s engine is superior, it looks like it can support more than an extremely dark corridor.

James Simmons
MindEngine Development
<a href="http://medev.sourceforge.net" target="_none">http://medev.sourceforge.net</a>


All the world lighting in HL2 precalculated gi. With Doom it''s all real time direct illumination. Both these engines were geared towards first generation dot3 hardware as a minimum, so either tradeoff is acceptable.

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