Heavenly Sword HDR Interview

[xbdestroya]

Alright, interview's back online (with some additions). :smoke:

http://psinext.e-mpire.com/index.php?categoryid=3&m_articles_articleid=599

[liver_kick]

Great interview, thanks to you and Marco for putting that together. Helped clear some of the more layman questions I had about HDR implementation.

8x aniso! A pean to my graphic whorish heart. :)

[Nameless]

Nice interview and discussion of HDR techniques...
I can't wait to get my hands on this title!

[CreativeWriter]

Fabulous interview. I barely understood a word, but it was fascinating... This is what I like best about our forum. Thanks xb!

[Dralor]

No bad seeing as I've spoken to Dean and Marco before through beyond3d. I have to say they are a good group. A bit crazy but good. Hey maybe I'll become that crazy got an assembly class to take next quarter:-p

[Hrama]

Ah, excellent interview indeed. I understood most of it (Thanks to spending time on this forum). Very impressive. Nice to know that he thinks that Cell has not yet been tapped into very deeply. Good stuff, thanks Xb!

[casualkiss]

Best article on the PS3 yet! I am not kidding.

The technical information provided (had to read it 3 times before I understood it) really outlined the comparable performance between xenos and the RSX FAR better than any fanboy hype ever could.

Regarding HDR, have you ever played "Black". It had some wonderful examples of how HDR can effect gameplay.

The fact that he is depending so much on shaders instead of memory (and even abandoning the built-in hardware effect "blending" really proves what developers have been saying... RSX is a shading beast!

[agentorange]

To bad because of the limitations of PS3 especially RSX and the RAM the frame rate can only be done on 30 fps and the maximum resolution is only 780p not the 1080 that Sont boast.

[Crossbar]

Great article!!!!
Ninja theory is a likeable company, I recommend reading through these features at their site: http://www.ninjatheory.com/index.php?option=com_content&task=blogsection&id=4&Itemid=52

They obviously put a lot at stake when they started the HS project. These guys got guts and brains.:clap:

BTW I started a thread at B3D on a topic brought up in the article, we'll see if it lends us some more RSX information.:unsure:
http://www.beyond3d.com/forum/showthread.php?t=31559

[Z]

smart interview indeed. I wish more interviews were as informative.

keep it up Xb. you da man!

[xbdestroya]

LOL, I was wondering when/how the article would reach B3D.

Leave it to you Crossbar to pursue your sick and twisted agenda! ;)

Anyway I think DeanA's (not DeanoC people, remember) response in that thread is right on the money, and is in line with what I've heard (not necessarilly from nAo either) that's not written in the interview itself.

To Crossbar's question of whether the framebuffer might be split:

I think he's simply saying that because RSX has access to two different memory pools connected via separate buses, as discussed here, it becomes possible to balance your rendering operations in order to get an effective amount of bandwidth greater than that available by just working only in VRAM.

So, for a framebuffer effect example, traditionally you may have all your source textures and destination buffer in VRAM. Reads from your source buffers and writes to your destination buffers all take place over the 128-bit bus to VRAM, so you potentially end up being bandwidth limited. As an alterative approach, if you moved one or more of your source textures over into XDR, you end up with a more balanced system that uses both XDR bandwidth and VRAM bandwidth, and as such is able to transfer more.

Cheers,
Dean

[PS3destroya]

Best article on the PS3 yet! I am not kidding.

The technical information provided (had to read it 3 times before I understood it) really outlined the comparable performance between xenos and the RSX FAR better than any fanboy hype ever could.

Regarding HDR, have you ever played "Black". It had some wonderful examples of how HDR can effect gameplay.

The fact that he is depending so much on shaders instead of memory (and even abandoning the built-in hardware effect "blending" really proves what developers have been saying... RSX is a shading beast!

That's the positive spin on it.

The negative spin would be, they're having to trade shading power to alleviate bandwidth concerns, which isn't ideal, especially for a machine where bandwidth is projected to be a big possible issue.

[Z]

the maximum resolution is only 780p not the 1080 that Sont boast.
when did Sony claim that HS would be running in 1080p? that said, the game could very well reach 1080i since most 720p media plays in 1080i.

there are games that will be in 1080p. Sony games that will do so thus far are Resistance, WarHawk and Untold Legends. and you know what? all those games will run at 60fps.

[xbdestroya]

LOL, welcome to the forum PS3destroya. ;) (more accurate would have been PSdestroya)

I don't see why it's unideal though; PS3 has tons of shading power, limited bandwidth. It gives up some of the shading power that would never form a bottleneck in the first place in order to free up bandwidth, which is limited. How does that equation not make sense in your book?

Anyway about the name, it's all good to spoof mine in reverse, but please I hope you're not here to simply bash Playstation and carry out an agenda; you could see where I might be concerned, especially since your name seems to take the additional angle of targeting me specifically.

I'm fine with whatever monickers so long as the posts themselves be constructive.

[Z]

awh, XB has a new little brother. how sweet.

*goes to make a Revdestroya account to join the family*

[edoshin]

I hope people do understand that depite your name, XBDESTROYA is in no way a destroyer of all things XB positive.

We have been given extraordinary access to the development process via the generosity of the HS team. There are no linear approaches to creating great games ie the brute force method simply b/c the console has advanced another generation. No matter how much muscle you put under the hood, there is never enough. What separates the great devs such as Naught Dog, and the Kojimas, are the approaches to which they arrive at ingeneous solutions. Those who pursue the brute force method are doomed to mediocrity and small thinkers.

[overclocked]

That's the positive spin on it.

The negative spin would be, they're having to trade shading power to alleviate bandwidth concerns, which isn't ideal, especially for a machine where bandwidth is projected to be a big possible issue.


The cost is only 2-3% per frame (counting for different clockspeeds) so thats not an issue at all i would say.

Edit

To add to XB post.

[xbdestroya]

I hope people do understand that depite your name, XBDESTROYA is in no way a destroyer of all things XB positive.

I would hope so. Hell, I'm almost never talking about XBox unless I'm defending it! :smoke:

Anyway I figure PS3D (see, 'PS' is just too weird a shorthand also, not like xb or xbd) chose that name either because he's familiar with me and wants to have some fun, or he thinks I'm this huge Playstation fanboy and wants to represent XBox here to 'counteract' me. Or he's a troll.

The first one I'm ok with, the second I'm lukewarm to pending more posts, and the third is just obviously no good.

Anyway pending a response from mystery man, let's try to keep things on topic. :)

[chrismt]

E-drama im E-mpire over a name...just let it play out instead of going reasons. Surprised you're still up too XBD ;-]

As to the interview, thank you for conducting it, as it was very informative on the implementations and different aspects of HDR. A couple of things stuck out to me though, namely was nAo a poster in these forums before, and what are the framebuffer effects you guys were talking about? I'm going to start my EE major this coming fall though, so maybe I'll be able to dissect the PS3 architecture a little more easily.

[liver_kick]

The cost is only 2-3% per frame (counting for different clockspeeds) so thats not an issue at all i would say.

Wow, thats a pretty good tradeoff!

From what I gleened from the convos over on B3D, the major issue "issue" with NAO32 seems to be that it isnt good (or even compatible?) with transparencies as opposed to opaque geometry, and thats a big reason why it wont suit every developer's needs, despite the high quality otherwise. Im pretty confused about this whole transparency problem though as its past my layman understanding of rendering, I'll leave it to the gurus to explain. ;)

[casualkiss]

Do you know if the developer was working with the real flex interface or the PCI stand-in? If so, perhaps the bandwidth limitations will be improved... at least for generation 2 games.

[tien69]

xbdestroya, I consider you the greatest mod alive, you have a relationship, and tolerance and wisdom that is unmatched on any forum. And I was coming here to read stuff from 3 years ago, so i know.

xbdestroya Offline:
PSINext forever Join Date: Sep 2004
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LOL, welcome to the forum PS3destroya. (more accurate would have been PSdestroya)

I don't see why it's unideal though; PS3 has tons of shading power, limited bandwidth. It gives up some of the shading power that would never form a bottleneck in the first place in order to free up bandwidth, which is limited. How does that equation not make sense in your book?

Anyway about the name, it's all good to spoof mine in reverse, but please I hope you're not here to simply bash Playstation and carry out an agenda; you could see where I might be concerned, especially since your name seems to take the additional angle of targeting me specifically.

I'm fine with whatever monickers so long as the posts themselves be constructive.




Dude gonna be trouble, just my opinion.

[agentorange]

So if you implement a full HDR thus it really mean that there will be big trade offs like Frames per second and resolution? So is this inevitable?

[ddaryl]

HDR lighting sound good

this doesn't

Marco: Our target resolution for Heavenly Sword is 720p with 4x MSAA, which we've already achieved. The frame rate target is not something completely set in stone at this time. Though our E3 demo was running at over 30 frames per second, I'm willing to bet the final game will run at 30 FPS. Hopefully this will allow us to push even more effects on screen.

I'm already frustrated with Xbox 360 games only achieving 30FPS in many of its games. It seems to me the industry is heading in the opposite direction when it comes to framrates. A fast fighting game like Heavenly Sword should be running at 60 FPS IMO.

[xbdestroya]

So if you implement a full HDR thus it really mean that there will be big trade offs like Frames per second and resolution? So is this inevitable?

Well, anything you implement is going to have a tradeoff (or cost rather) somewhere in the system. On RSX, the 'easy' way to do HDR is just to go via hardware and FP16. The big cost here is that it uses a lot of bandwidth and maybe doesn't allow MSAA on RSX at the same time. I say maybe because everyone seems pretty vague on answering that question when asked, but NV40, NV47... they have that problem.

By going the NAO32 route, they give up the hardare blending ability in order to regain half the HDR bandwidth expenditure for use elsewhere, like their MSAA for example. And to allow MSAA period if RSX otherwise does not allow it.

They could hit higher frame-rates if they wanted, but they rather have the game look pretty; Marco even alludes to that at the end. As for 720p, I just expect that to be the norm. 1080p will be great when it shows up from time to time, but really for a game sold 'today,' 720p is going to be the resolution the customer will play it at, and the lower resolution will, again, allow more effects on screen, stable frame rates, etc etc...

@Tien: Many thanks; I'm touched! :worthy:

[satriales]

Unfortunately, current low-cost display technologies (common LCDs, CRTs, etc..) can't properly display an HDR image, so we need to go through a process called 'tone mapping' to remap our image to an LDR (Low Dynamic Range) image in order to display it on a screen.
Is this due to the low contrast ratios on most tv's?
Are there any tv's available that do properly display HDR images?


when did Sony claim that HS would be running in 1080p? that said, the game could very well reach 1080i since most 720p media plays in 1080i.Sony never made such claims, but Deano C did say the indoor enviroments in HS easily ran at 1080P. I expect the final game will be 720P just because it is a first gen game and they haven't got the time to optimize it for 1080P and 60FPS. I'm sure as they get to know the PS3 more developers will be able to get better framerates and a higher resoloution, but for games released around launch it's probably too much too expect.

[Pumpkin Head]

Very good read, really can't wait for this game,

[yoshaw]

Great interview Xb. Hope to see more of these exclusives for PSI-Next from Ninja Theory. We love 'em :)

[overclocked]

Wow, thats a pretty good tradeoff!

From what I gleened from the convos over on B3D, the major issue "issue" with NAO32 seems to be that it isnt good (or even compatible?) with transparencies as opposed to opaque geometry, and thats a big reason why it wont suit every developer's needs, despite the high quality otherwise.


Yeah hope nAo can aswer some more. Im not 100% sure but i think they are also using FP16 HDR sometimes, im pretty sure i read that, anyway XB can drag him here elsewhere. ;)

So if you implement a full HDR thus it really mean that there will be big trade offs like Frames per second and resolution? So is this inevitable?

Well as you see its quite the other way around or have you even bothered to read it?
There will always be tradeoffs but "wasting" 2-3% of your shading to get twice the avaliable bandwidth is a Win/Win situation IMO, cant imagine how you can come to another conclusion really.

[Heinrich4]

I like hear RSX can acess another bus(by flexIO or other?) beyond local VRAM 22,4GB/seg.

[OmniCloud]

Isn't Ninja Gaiden and GoW run at 30FPS? I don't think we need to go much further than that in terms of speed-you'll lose control of the character that way! Besides-If this game runs as fast as the E3 demo while looking even prettier on release-I won't have any complaints.

[Crossbar]

Yeah hope nAo can aswer some more. Im not 100% sure but i think they are also using FP16 HDR sometimes, im pretty sure i read that, anyway XB can drag him here elsewhere. ;)
I guess it's this post by DeanoC you were thinking of:
Unfortately people seem to think that one framebuffer and colour space per game is the only option. We use several in a single frame... NAO32 opaque, FP16 RGB HDR alpha, ARGB8 RGB LDR alpha.
http://www.beyond3d.com/forum/showpost.php?p=731806&postcount=53

Here are a few old posts by nAo about the Cell RSX interaction, which I found to be quite interesting, hand picked for your convinience :):
http://www.beyond3d.com/forum/showpost.php?p=510049&postcount=89
http://www.beyond3d.com/forum/showpost.php?p=510062&postcount=93
http://www.beyond3d.com/forum/showpost.php?p=510110&postcount=105
http://www.beyond3d.com/forum/showpost.php?p=510162&postcount=118
http://www.beyond3d.com/forum/showpost.php?p=510367&postcount=133

and this one about the NAO32 Image Quality:
http://www.beyond3d.com/forum/showpost.php?p=730501&postcount=19

[RavenFox]

+Rep for good ol XB. What a wonderful wonderful interview. I was all giggly like a little kid lol. THe tech info man I love it.

[VG Aficionado]

Hmmm...

This right here tells me there is no reason to continue talking about this with you. You obviously have no idea what the thread is discusing and just felt like jumping in and adding your wo sense into a discusion you didn't bother to read .
Yeah..I'm the one who has no idea :) too bad you're the one that avoided all my questions on specific technical details http://www.beyond3d.com/forum/images/smilies/icon_rolleyes.gifDéjà vu :cowboy:

[edoshin]

Did we know who nAo was back then?

[xbdestroya]

Yeah we knew; at least some of us did. :)

[Chrome]

yep I did aswell :D, he's a good guy.

[edoshin]

I think its to the benefit of devs who post to remain anonymous .. or at least to the specific compnay they work for. Otherwise they get bombarded, or may get in trouble within their organization for revealing sensitive information. The NT sword team has given us unprecedented access in that regard.

[Z]

yep I did aswell :D, he's a good guy.
ah, yes. my pupil turned out well. er, just don't tell him I said that. he would never admit it.

[liver_kick]

I guess it's this post by DeanoC you were thinking of:

http://www.beyond3d.com/forum/showpost.php?p=731806&postcount=53

Interesting. Again this is a bit over my head so pardon the base terminology, but the way that sounds is they can basically work around the opaque limitation and essentially fit to the needs of the frame? If thats the case, Im wondering if there are any other drawbacks that would prevent a developer from always taking this NAO bandwith saving approach? IIRC Deano mentioned it wouldn't suit the engine Guerilla is working on for example. But I cant imagine a 2-4% hit on shaders being a roadblock for most studios needs. Is there something Im missing (quite likely ;))?

[MaceSin]

Isn't Ninja Gaiden and GoW run at 30FPS? I don't think we need to go much further than that in terms of speed-you'll lose control of the character that way! Besides-If this game runs as fast as the E3 demo while looking even prettier on release-I won't have any complaints.

Nope, both were 60FPS...

The whole 30FPS-60FPS doesn't really bother me, so eh.

[satriales]

Nope, both were 60FPS...

The whole 30FPS-60FPS doesn't really bother me, so eh.
I never used to be bothered by the whole 30/60fps thing, but I've started to notice the difference recently and some 30fps games look annoyingly juddery.

With some games it doesn't make too much difference but generally I would prefer ugly 60fps over a prettier 30fps.

[OmniCloud]

Yeah..but those games are like the Creme of the Crop as far as Action Adventures go-I don't understand how a developer can make an Action game that doesn't run as smooth as last gen titles? Am I missing something here? Or just jumping the gun a bit?

[woundingchaney]

LOL pre-emptive strike 60fps > 30fps (anyone remember that).


A solid 30 fps is just fine and people should really let the notion go (it has been grossly over-exaggerated). I would personally rather have a solid 30 fps than a "bouncy" 60 fps.


I think the game is shaping up well and is going to be a definite purchase for me.

[GUNDAMSEED]

Well i won't be getting this any more, i am a frame rate whore. If DMC4 end up at only 30fps then i know all hope is lost .

[Z]

I would personally rather have a solid 30 fps than a "bouncy" 60 fps.
but some of us like dem bouncy. oh, we're talking about frame rates. sorry. yes, 30 solid is better than 60 bouncy. *never thought I'd say that*

[woundingchaney]

Well i won't be getting this any more, i am a frame rate whore. If DMC4 end up at only 30fps then i know all hope is lost .
Why does it matter, infact the only way you would know the difference between a solid 30 fps and a solid 60 fps would be if a dev told you.

[section]

Oh you can tell the difference between 30 and 60 fps awright. Even between 60 fps and 300 fps. In PC world the frame rate owns ya.

[xbdestroya]

In the PC world it's never locked though as it will be in this instance; it's always jumping around. You knwo if you're hitting 30 FPS in a PC game, it actually means you're hitting 20 fps one minute and 40 the next. I think this situation here is much improved over that.

[woundingchaney]

Oh you can tell the difference between 30 and 60 fps awright. Even between 60 fps and 300 fps. In PC world the frame rate owns ya.
Yeah because the majority of people that proclaim framerate as a godsend are lucky to even hit 60fps some of the time with their rigs.

Framerates for the pc is more of a benchmarking and bragging rights ordeal.

My previous statement may have been somewhat harsh, I suppose some trained people can detect the difference between 30 and 60 fps, although for the most part I cant believe people are making this out to be the issue that it has become.

[woundingchaney]

In the PC world it's never locked though as it will be in this instance; it's always jumping around. You knwo if you're hitting 30 FPS in a PC game, it actually means you're hitting 20 fps one minute and 40 the next. I think this situation here is much improved over that.
I agree

[yoshaw]

Why does it matter, infact the only way you would know the difference between a solid 30 fps and a solid 60 fps would be if a dev told you.

I disagree mate. The difference between 30fps and 60fps can be easily seen by the naked eye IMO. A constant 60fps is butter smooth compared to a stable 30fps. There is something about the 60fps figure that just makes it the ideal smoothness level for the eye to see. I can't point out what it could be but it sure is very pretty.

For the record, I don't mind a stable 30fps. Anything double that is always a plus ofcourse ;)

[woundingchaney]

I disagree mate. The difference between 30fps and 60fps can be easily seen by the naked eye IMO. A constant 60fps is butter smooth compared to a stable 30fps. There is something about the 60fps figure that just makes it the ideal smoothness level for the eye to see. I can't point out what it could be but it sure is very pretty.

For the record, I don't mind a stable 30fps. Anything double that is always a plus ofcourse ;)
LOL yeah I noted that my statement was somewhat harsh a couple posts down from the one you quoted.

:uhh:

[GUNDAMSEED]

i can tell , some people can just tell better than others .For certain games 30 is okay . But for action games and races 60fps is a must .

[Crossbar]

i can tell , some people can just tell better than others .For certain games 30 is okay . But for action games and races 60fps is a must .
I think the coming generation of games will use motion blur in a way that will relax the 60 fps requirement. Just look at the stills from Motorstorm, they look pretty blury, but I´m sure it looks great when you are actually playing the game.

[fknuckle]

Nice little read--


If they can keep the fps to atleast a constant 30fps during the large scale battles,i'd be ok with that--- If it went to a max payne level of frame-rate,(where there were times of EASILY below 30fps)it would be very frustrating and annoying.

[tien69]

LOL pre-emptive strike 60fps > 30fps (anyone remember that).


A solid 30 fps is just fine and people should really let the notion go (it has been grossly over-exaggerated). I would personally rather have a solid 30 fps than a "bouncy" 60 fps.


I think the game is shaping up well and is going to be a definite purchase for me.


Amen, constant 30fps is cool, choppiness interrupts the 'immersion' of any game. I sure do hope they up the GDDR3 RAM though.

[gljvd]

Seems like he let it slip that the rsx is indeed based off the g7x line up

We believe it's a very good trade-off. Furthermore, it enables HDR rendering and multisample anti-aliasing on GPUs that do not natively support AA with floating point render targets such as FP16 and FP32.


Anyway , I will leave my comments about the actual quality of nao24/32 out of this

[Red_Eyes]

That's the positive spin on it.

The negative spin would be, they're having to trade shading power to alleviate bandwidth concerns, which isn't ideal, especially for a machine where bandwidth is projected to be a big possible issue.

And the extra negative spin would be, it's impossible for the 360 to even do this, meanwhile, the PS3 can do this through trading with shading power.

[Red_Eyes]

HDR lighting sound good

this doesn't

I'm already frustrated with Xbox 360 games only achieving 30FPS in many of its games. It seems to me the industry is heading in the opposite direction when it comes to framrates. A fast fighting game like Heavenly Sword should be running at 60 FPS IMO.

Well, if with 30fps, they will be able to add more on screen effects to HS, then it's worth it.

[liver_kick]

Seems like he let it slip that the rsx is indeed based off the g7x line up

Earth-shattering revelation.

Anyway , I will leave my comments about the actual quality of nao24/32 out of this

*insert 1600x1200 rolls eyes emoticon here*

[Rukawa]

As long as the frame is 30 fps without slow down + motion blur it doesnt matter
To NT please give us temporal supersampling for HS2

[cliffbo]

LOL pre-emptive strike 60fps > 30fps (anyone remember that).


A solid 30 fps is just fine and people should really let the notion go (it has been grossly over-exaggerated). I would personally rather have a solid 30 fps than a "bouncy" 60 fps.


I think the game is shaping up well and is going to be a definite purchase for me.

yes i vaguely remember that.... time will tell :)

[chrismt]

So what were the framebuffer effects referred to in the interview? I'm just not sure what that term means.

[xbdestroya]

I liked the interview on the front page with the guy from HS, very interesting in my oppinion but now I'm curious why Dean named it NAO32. Has he ever answered this?


Hey Danji, I'm answering your question here so that your thread doesn't go off topic. :)

Anyway it's pretty straight forward - Dean named it NAO32 after it's inventor Marco (the interviewee) who's forum name in most places is nAo. The 32 comes from the fact that it's an 8-bit per component RGBA space that's used to implement it.

[edoshin]

Anyway , I will leave my comments about the actual quality of nao24/32 out of this

Please do as u are not qualified to make any relevant points ..

[Nerve-Damage]

Alright, interview's back online (with some additions). :smoke:

http://psinext.e-mpire.com/index.php?categoryid=3&m_articles_articleid=599

Nice interview bud!! :cheers:

(+rep)

[yoshaw]

Some new video footage off of the Sony E3 Press Kit

Xvid - 11mb - 42 seconds
http://www.savefile.com/files/2397057

Screengrabs from trailer
http://xs302.xs.to/xs302/06261/HSword_01.jpg.xs.jpg (http://xs.to/xs.php?h=xs302&d=06261&f=HSword_01.jpg) http://xs202.xs.to/xs202/06261/HSword_02.jpg.xs.jpg (http://xs.to/xs.php?h=xs202&d=06261&f=HSword_02.jpg) http://xs202.xs.to/xs202/06261/HSword_03.jpg.xs.jpg (http://xs.to/xs.php?h=xs202&d=06261&f=HSword_03.jpg)

[VG Aficionado]

The quality is nice, but there's nothing new in there.

[yoshaw]

Have they shown Nariko jumping off the 50foot falling cliff elsewhere at E3? I thought that was a first. Psssh could be me missing it entirely during E3. In which case, my bad.

[VG Aficionado]

Have they shown Nariko jumping off the 50foot falling cliff elsewhere at E3? I thought that was a first. Psssh could be me missing it entirely during E3. In which case, my bad.Yes, I've definately seen that before. That was an impressive moment BTW :cowboy:

[Smokey]

excellent interview there xbd :)

[cpiasminc]

Seems like he let it slip that the rsx is indeed based off the g7x line up
How is this news? Hasn't this been about 95% certain for at least a year?

The 32 comes from the fact that it's an 8-bit per component RGBA space that's used to implement it.
It's not 8:8:8:8 ARGB... it's 16:8:8 LogLuv. Still fits in 32-bits per pixel is the point.

Anyway , I will leave my comments about the actual quality of nao24/32 out of this
You might want to read Ward's paper. Every argument you've had on this was made up of preconceived notions drawn solely on bit count and not paying any attention to the distribution of data. If you'd paid attention, there are more bits of precision allocated to the HDR component in NAO32 than in FP16. Certainly NAO24 has much more visible quantization error, but then it's still about equal to FP10 (and still beats FP10 by far in dark regions, though that's not saying much).

The errors that DO occur are not due to precision so much as the fact that RGB is not perceptually mapped while LogLuv is. So even though the RGB gamut is a subset of the Luv gamut, the representations of the spaces are uneven relative to each other, which means that the quantization in the logarithmic luminance domain does not quantize the same in the linear RGB domain. In any case, that does yield some chromatic error, but then, so does any HDR tone mapping operator, you're talking about something that is more visible if the tone mapping operator pushes the output colors more towards the bright end.

BTW, LogLuv paper -- http://www.anyhere.com/gward/papers/jgtpap1.pdf

The negative spin would be, they're having to trade shading power to alleviate bandwidth concerns, which isn't ideal, especially for a machine where bandwidth is projected to be a big possible issue.
True, but when was the last time you heard of a GPU that wasn't bandwidth constrained in some way? If you think GS/GE and Xenos are NOT constrained because they have eDRAM, then you're crazy.

The cost of the extra shader instructions is relatively small, and probably even smaller on RSX compared to Xenos since you can co-issue more instructions in the pixel pipes -- even aside from that is just the fact that as the shader gets more complex, the relative cost of the conversion goes down since it's a fixed load at the end. There are, of course, the simpler pixels, but those are usually transparent, which gets handled in a separate pass without any LogLuv encoding.

[tien69]

Ah cpi, i see why they adore you so on here, kudos.