What is missing in GPU hardware to do classic Global Illumination algorithms?

[Shifty Geezer]

didn't they just add ambient lightinh

No. Ambient light has absolutely no details. The wall in shadow would be a plain, flat brown colour is it were ambient light. The shelves would be a plain flat grey in the shadows wihtout the darness in the corners of each box. Now this is ambient light in the true sense, so in that you are right, but what we call ambient light in every day conversation (as you do, getting the bus and talking to the driver about ambient light) is called Global Illumination or radiosity in computer graphics, and Ambient Light is a constant universal illumination per pixel added to each surface.

 

[ShootMyMonkey]

Most secondary interactions of light result in lighting that is "smooth" in nature, so ambient light is an approximation that draws on the assumption that it will be infinitely smooth (that is to say, no variance). It does mean, though, that the vast majority of recursive light interactions (save for LS+D paths) can be done at pretty low sampling resolution and still get you reasonably accurate results. This is also part of the idea with photon mapping, which is actually a pretty sparse sampling for the global illumination side of the problem -- only caustics (LS+D) get fine sampling resolution.

 

[3dcgi]

didn't they just add ambient lightinh

Ambient lighting in rendering is just a hack to fake global illumination.

 

[_phil_]

Ao without any lights gives this:
http://www.neilblevins.com/cg_education/ambient_occlusion/ambient_occlusion_01.jpg

this is too an AO only pass :
http://daniel.mueri.net/gallery/plant-room/OA.jpg

this too:
http://brentogara.com/img/art/ph34rT3hAmbientOcclusion.1.jpg

this is AO +one directionnal light:
http://www.ixbt.com/soft/images/ao/24.jpg

 

[Shifty Geezer]

this is too an AO only pass :
http://daniel.mueri.net/gallery/plant-room/OA.jpg

Won't it be great when games are lit as well as this in realtime!

 

[_phil_]

Won't it be great when games are lit as well as this in realtime!

no lighting at all here.
Just AO and a lot of geometric detail to catch occlusion.In fact ,if you set up a FG (final gathering) solution to behave like a simple AO ,you can catch the details that are in the normalmapps (a contribution of the per-pixel normals into AO).

 

[Fafalada]

Also, precalculated occlusion will miss all the object interaction, which is a very important part of the visuals.

If you are dealing with environments like PGR3, which are 95% static, you're not missing much of anything.
What little contribution cars give to AO over the static bgr has been faked in games for like a decade now (just sticking a dark blob under the car in addition to the shadow from light sources goes a long way in creating the illusion).

 

[Shifty Geezer]

no lighting at all here.
Just AO and a lot of geometric detail to catch occlusion.In fact ,if you set up a FG (final gathering) solution to behave like a simple AO ,you can catch the details that are in the normalmapps (a contribution of the per-pixel normals into AO).

The scene is being 'lit' by an ambient occlusion algorithm. Of course AO is really finding shadows rather than applying lights, but if there was no 'light' in the scene, it'd be all black! Hence it's is lit with a ubiquitous light source, using AO to add the shadows as it were.

It'd be nice to have a game rendered just like this, I think, with no textures or colours. There's that B&W game coming for Wii. The style of this AO is so realistic and artsy like high contrast B&W photography, in a deep RPG it'd go well IMO.Any speculations how close this gen could come if the CPU and GPU's were thrown very much into the task?

 

[Platon]

It'd be nice to have a game rendered just like this, I think, with no textures or colours. There's that B&W game coming for Wii. The style of this AO is so realistic and artsy like high contrast B&W photography, in a deep RPG it'd go well IMO.Any speculations how close this gen could come if the CPU and GPU's were thrown very much into the task?

I have been thinking the same thing. A black and white game were you put most of the assets to geometry lighting and textures take the back seat...

 

[Shifty Geezer]

You'd free up loads of resources, memorywise. The texture units on GPU would be redundant though, wouldn't they? Would that be power lost? In RSX asuming they'd coupled to the pixel shaders, you'd be running at 100% pixel shading. On Xenos the texture units are decoupled so without texturing you'd have nothing. Tell a lie, you'd have normal/parallax maps to apply. Could these work with AO on a GPU?
You could develop the game around maybe the idea of Claymation, where everything's made out of Plasticine, maybe with some hardcore geometry morphing.

 

[Acert93]

You'd free up loads of resources, memorywise. The texture units on GPU would be redundant though, wouldn't they? Would that be power lost? In RSX asuming they'd coupled to the pixel shaders, you'd be running at 100% pixel shading. On Xenos the texture units are decoupled so without texturing you'd have nothing. Tell a lie, you'd have normal/parallax maps to apply. Could these work with AO on a GPU?
You could develop the game around maybe the idea of Claymation, where everything's made out of Plasticine, maybe with some hardcore geometry morphing.

Not to go too far on a tangent, but I think the general principle [of limiting color palette] is applied in a lot of great looking games. The minimalist grey/black/brown/etc schemes may set a mood, but they also seem to be used at times to limit the palette. RE4 comes to mind among others. Shadow of the Collosus, while I have not played it, the videos I have seen all tend toward a more drab color scheme, which of course is offset by the shere size of the bosses.

Anyhow, I am with you guys. Some stylized games using a grey tones black-and-white scheme like the above would be neat, if not a needed change of pace.

 

[Laa-Yosh]

If you are dealing with environments like PGR3, which are 95% static, you're not missing much of anything.
What little contribution cars give to AO over the static bgr has been faked in games for like a decade now (just sticking a dark blob under the car in addition to the shadow from light sources goes a long way in creating the illusion).

I'm talking about enviroment-car and car-car interaction.

 

[Laa-Yosh]

Traditional ambient light is totally constant, so it gives no shading and flattens the scene - thus it is not used widely...
Image-based ambient lighting, from an enviroment, is better. This is what gets combined with ambient occlusion to create very soft shadows. Another trick is to modify the surface normals based on the least occluded light direction to change the result of the enviroment map lookup.

 

[Squeak]

Not to go too far on a tangent, but I think the general principle [of limiting color palette] is applied in a lot of great looking games. The minimalist grey/black/brown/etc schemes may set a mood, but they also seem to be used at times to limit the palette. RE4 comes to mind among others. Shadow of the Collosus, while I have not played it, the videos I have seen all tend toward a more drab color scheme, which of course is offset by the shere size of the bosses.

Anyhow, I am with you guys. Some stylized games using a grey tones black-and-white scheme like the above would be neat, if not a needed change of pace.

But it's already been done to death for like the last ten years FFS!!
On the contrary, we really need a loooong break from that self-aggrandizing style.