Doom3 Rendering

[Guest CRiZ]

Hello beautiful Doom3 forum people. 8 )

For the topic of my big paper for my Technical Writing class, I've chosen to describe the visual enhancements made to each of Id Software's games. I'm detailing the advances made from the Wolfenstein Engine all the way up to what is known and expected of the Doom3 engine.

I know a lot of you write very intelligent, meaningful posts... and a lot of you are flaming, spamming, newbie llamas. I'm hoping to get some responses from the former mentioned category.

Does anyone know of any good technology resources and descriptions of the graphics engines used in any of Id's games? I'm especially looking for info concerning Quake3 because that, surprisingly, seems to be the most difficult infomation to come about.

One question which I can't find the answer for: Does Quake3 (or Doom3) use ray-TRACING(allows reflections, refractions) or ray-CASTING(faster and does not allow reflections, refractions)?

I know that mirrors are a new technology in Quake3 but I wasn't sure that this was raytraced reflections or some other trick.

Thank you all. This report is due next Wednesday so I would really appreciate the help of all the woderful cult followers of Id Software!!

[Zaldron]

Since DooM3´s using pixel shaders, the answer is both.

For one side, when you call a pixel shader instruction, you´re doing it to calculate lighting in a specified point in the universe. This point´s not one on the monitor´s plane, but belongs to a z-buffered triangle. The engine raytraces the framebuffer (your current work of space limited by the resolution), checking to who belongs each pixel.

After that, the engine raycasts as many vectors from each light as pixels lited by that light. Do some math to calculate the final lighting condition, and then apply it over the current pixel. Expect some nasty framerate drops while increasing resolution.

In 640x480 there are 307,200 light points to calculate, while in 1024x768 there are 786,432.


UPDATE : About the mirrors. Quake 3 uses a shader that invokes a camera. The camera´s results are calculated in an extra buffer (one more pass) and then fills the "void" of the mirror brush with that image.

Mirrors are "camera-monitors" where the camera´s actually in front of the mirror. The same tech was used in STV-EF for security cameras, and for some crazy stuff in Alice´s skies.

[Lord FlatHead]

Hey Zaldron, speaking of technology, how's that article coming along ?

[Zaldron]

I´m fixing grammar and finishing the footage frame-by-frame v2.0

You could get it as soon as today, altough I don´t promise anything...

[danarchist]

Unreal Tournament used mirrors, but you could only see them if you have good acceleration. I don't know how they made them, but they looked realistic. We've sure come a long way since the Duke Nukem mirrors (you had to make a huge room behind the mirror so the computer could make duplicates of everything in the other room).

[Guest CRiZ]

Zaldron said:

Awesome, thanks Zaldron.

Once again, and sorry to be annoying, but where do you get this information?

It's hard to find good technical URL's.

[Zaldron]

I gathered this information up based on my innate gaming development knowledge (4 years coding/drawing for games), the tons of info you learn while using 3D Studio, and the tech talk on the diverse modding tutorials.

I don´t know any URLs were to go, altough you might find info on www.gamedev.net

[Guest DonNigera]

Since when is mirroring a new technology?

Didn't Duke Nukem 3D have mirror's in the bathroom?

I also recall Resident Evil 1 having a mirror or two!

So?