Talk:Unified lighting and shadowing

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Contents 1 Slightly inaccurate... 2 Issues 3 Fair use rationale for Image:Doom3Marine.jpg 4 Fair use rationale for Image:Quake3Screenshot.jpg

[edit] Slightly inaccurate...

"Doom 3 uses a unified model that generates the lighting and shadows for everything at run-time. This means that any lights will affect the whole scene and not only certain parts. This may include self-shadowing via shadow volumes, where characters can cast shadows on themselves, for example the shadow cast by the marine's chin onto his neck."

Firstly, this statment is not an accurate definition, several previous games have done this, including Quake 3 which is quoted as using an 'old model' here. Also, in Doom 3 the shadow volumes can be pre-generated by the map editor for the static lights casting from static geometry, the shadows are only recalculated for the dynamic objects or dynamic lights. I replaced it with the more accurate description of a unified lighting model:

"Doom 3 claims to use a unified model, which renders every triangle using the same lighting mechanism, regardless as to whether it originated from a model, or map geometry. This is not strictly true as some models are marked with a 'don't self shadow' flag, custom material shaders can allow different lighting mechanisms to be employed on different surfaces (most often a reflective cube map effect), and the point sprite effects (such as explosions) are totally unlit. A renderer using a truly unified lighting system would use an identical set of lighting calculations for every pixel on the screen and would not make such distinctions, although Doom 3's lighting is certainly far 'more unified' than previous games, there is still much more which can be done on recent and future hardware to improve the consistency of lighting in games."

"Doom 3 doesn't use OpenGL's built in system, instead, it uses its own system which gives better quality and more accurate illumination than OpenGL's current lighting model."

I altered this a little, since the OpenGL lighting model isnt likely to ever change to ensure backwards compatibility, so I replaced 'current' with 'default'.

"Shadow volume - the general technique for dynamic shadows"

Shadow volumes are ONE technique for dynamic shadowing, a more popular technique is infact shadow mapping, which doesnt rely on any volume generation, but instead is based on depth information rendered into a cube map for a point light, or regular texture for a projected light, from the point of view of the light source. Another, but less important (due to high computational cost) technique is raytracing.

--Jheriko

[edit] Issues

This needs a rewrite, but I'm a bit pressed for time to do so properly, so I'll list some notes here.

Regarding "Doom 3 does not appear to use OpenGL's built in lighting algorithms". This isn't noteworthy. Like all recent OpenGL-based games (save [often budget-] titles compatible with non-GLSL-capable hardware), Doom3 utilizes GLSL, which enables the client application to directly control lighting calculations (i.e., utilizing Blinn or Oren-Nayar algorithms). The situation is the same with DirectX, where games eschew the fixed pipeline for HLSL (the DX equivalent to GLSL).

Regarding "A renderer using a truly unified lighting system would use an identical set of lighting calculations for every pixel on the screen and would not make such distinctions." This isn't necessarily correct. Different surface material characteristics often require slightly different formulas, and some surfaces can be slightly algorithmically optimized (i.e., simplified specular computations). All of this takes place in GLSL and is executed on the GPU. Too the engine, it all geometry is effectively run through the same lighting pipeline.

Regarding "This is not strictly true as some models are marked with a 'don't self shadow' flag..." Not self-shadowing is an artist option, not a special engine codepath (that is, not a special-case scenario requiring unique processing, thus disqualifying the "unified" adjective). Keep in mind that lighting and shadowing are technically two distinct processes, and given the flag to not self-shadow, portions of geometry simply skip any shadowing instructions, and the lighting process is still utilized as normal. Zombie81 07:26, 18 April 2007 (UTC)

[edit] Fair use rationale for Image:Doom3Marine.jpg

Image:Doom3Marine.jpg is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.

Please go to the image description page and edit it to include a fair use rationale. Using one of the templates at Wikipedia:Fair use rationale guideline is an easy way to insure that your image is in compliance with Wikipedia policy, but remember that you must complete the template. Do not simply insert a blank template on an image page.

If there is other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images uploaded after 4 May, 2006, and lacking such an explanation will be deleted one week after they have been uploaded, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you.

BetacommandBot 23:27, 13 September 2007 (UTC)

[edit] Fair use rationale for Image:Quake3Screenshot.jpg

Image:Quake3Screenshot.jpg is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.

Please go to the image description page and edit it to include a fair use rationale. Using one of the templates at Wikipedia:Fair use rationale guideline is an easy way to insure that your image is in compliance with Wikipedia policy, but remember that you must complete the template. Do not simply insert a blank template on an image page.

If there is other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images lacking such an explanation can be deleted one week after being tagged, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you.

BetacommandBot (talk) 09:09, 21 January 2008 (UTC)