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LaBasX2

Doom 3

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Hi! I''ve read a bit about the Doom3-engine in some interviews with John Carmack and I''m wondering how he wants to create his light effects without using lightmaps. I think he won''t just use vertex lighting, that would certainly look too cheap. Furhtermore I''ve heard about the opinion of some people who were allowed to see the engine in action. They all mention the amazing light effects. So John must have a completely new technique, or at least I don''t know how to create light effects without lightmaps or vertex lighting. Does anyone know any alternatives for lightmaps or has anybody any ideas what John Carmack could have done for the Doom3 engine?

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Guest Anonymous Poster
Where did you read Carmack''s interview about Doom3?

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I remember seeing one of Carmack''s .plan files mention using the 3D texture feature for (dynamic) lighting... I think he said that although it turned out better than expected, it still wasn''t a great lighting method??

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Hi everyone. I think he mentioned stensil buffer techniques would be used. At any case, there have been some independant demos done by other people that use some of these methods to create totally dynamic lighting. Let me see if I can find a URL, so you can download an example for yorself.

...Sorry, it''s lost somewhere, and I can'' find it. It was a demo by Jon Olav Bjorndal, and it used shadow voumes and stensil buffers to render a small area and a quake model with completle dynamic, acurate shadows. I found it over on flipcode, in their "Image of the Day" catagory. They might have it still listed somewhere in their archives, if you feel like looking.

I just downloaded a NVidia paper, which describes a facinating alternate method that makes use of depth buffer for each light, sort of triangulated with the users view point. It delivers shadows independant of object complexity-- you don''t get a big from calculating the volume of a complex object. At least, I think that''s what they meant. So check them out, too.

LaBasX2, you''re probably right about him not using vertex lighting-- traditionally, Carmack has always been for textures over lots of geometry. I actually just finished a really, really crappy engine that uses completely dynamic shadows on a per vertex basis. It was kind of fun, but the results would hardly be publishable on a comercial level.

The trick you have to keep in mind, is that Carmack said that you''ll get a rather large boost in performance for any geometry that you can keep away from the CPU (and keep inside the graphics card). So, he''s not only come up with a fast algorithm, but he''s found a way to do the majority of it IN VIDEO HARDWARE. Yikes...

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Well, here''s the link to that dynamic shadow Image Of The Day at flipcode. You can download the sourcecode and binaries from there.

http://www.flipcode.com/cgi-bin/msg.cgi?showThread=12-05-2000&forum=iotd&id=-1

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Hi!

Thanks a lot for your relpies!

SH, your response really helped me to figure out an alternative way of doing lighting. The link with the demo is really cool. Thanks! Might be Carmack is using a similar technique. I'll also go get the paper you mentioned (is it the one called "BRDF-based lighting" ?).

By the way, what are 3D textures?

cu

Edited by - LaBasX2 on January 11, 2001 9:28:34 AM

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3D textures are exactly what they sound like: 3-dimensional textures. Instead of a rectangular image, picture a cube, made up of little cubes for texels.

Vertex lighting doesn''t always look cheap; it just depends how many vertices you use. In my game, wall3D, I use a grid of 14x7 vertices to represent a simple flat rectangular area, and it results in a really nice spotlight effect.

My game also has real-time shadows and reflections, and IMO it looks at least as good as pre-rendered lightmap stuff. You can get it here if you want to take a look.

http://www.geocities.com/ben32768

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Hi there,

if you subdivide a polygon enough with vertex lighting
then the result is comparible with phong shading.

The other option for lighting is to use the option
in OpenGL1.2 for a seperate specular color which
is applied after texturing to give a much more
realistic specular highlight which lies on top
of the texture rather than underneath it.

Hope these ideas may help.

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