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High Dynamic Range (HDR) Technology Analysis
THG writes "CoolTechZone.com has published an analysis of Valve's High Dynamic Range, or HDR, technology that enhances graphics in video games. This new video/gaming graphics technology is expected to debut soon with Valve's Half-Life 2: Lost Coast title. According to the article, 'HDR, or High Dynamic Range, is a lighting process that's been designed to emulate in-game or artificially generated lighting to closely mirror the changes we see in the real world. In simpler terms, HDR allows you to make the objects brighter by allowing them to use the full brightness capabilities of the monitor and not just the brightness level at which they have been shot with (or rendered with) in the scene.'"
HDR (High Dynamic Range) Technology: An Overview
Written by Varun Dubey
Manufacturer: Various
Monday, 31 October 2005
(Review) - We've all played Half-Life and it's sequel Half-Life 2. The difference between the two games, in terms of graphics, is tremendous, and now Valve has gone ahead and updated the gaming engine to give you a level of detail and realism that you thought wouldn't be possible until perhaps the next round of game releases.
HDR, or High Dynamic Range, is a lighting process that's been designed to emulate in-game or artificially generated lighting to closely mirror the changes we see in the real world.
In simpler terms, HDR allows you to make the objects brighter by allowing them to use the full brightness capabilities of the monitor and not just the brightness level at which they have been shot with (or rendered with) in the scene.
HDR is, by definition, the ratio of the largest to lowest measurable value of a signal. As of today, the 16-bit formats use color component values from 0 (for black) to 1 (for white), but you can't define colors with increased vibrancy and shine by inputting value 2 for white to make it whiter than its traditional shade. Think about your breathing. That's right - inhale and exhale voluntarily. This can limit lighting effects such as the glint on the metal blade of POP Warrior Within.
Using HDR, you can specify values that are far outside the redundant 0-1 ranges we are used to currently. To give you an everyday example, when you drive on a sunny day, it often happens that the minute you come out of the tunnel, the sunlight seems blazingly brilliant as your eyes take sometime to adjust to the difference in the light intensities. In a game like NFS, replicating this realistic phenomenon is difficult and nearly impossible for the lack of the ability to specify whiteness beyond level 1, but with HDR, you can accomplish just that, which is why it's important to gamers that demand realism from their games.
Up until now, such effects were being achieved by a technique known as Blooming. This technique allows you to let the light from an overly bright object spill on to the particles around it, thereby making them appear brighter and ensuring enhanced visibility in titles.
The process, however, does not just work to increase the brightness of whites, but it also ensures that the blacks appear blacker and deeper while enhancing the subtle details of the image.
How does it work? Traditionally, images are stored in the RGB format, where each pixel knows exactly how much of these three colors it's supposed to display to give you accurate images.
The problem with this is that an image might be very bright, but how much of that brightness we see is dependent solely on the monitor we are displaying it on and no monitor in the world today can display anywhere close to the range of brightness levels that we can experience through our eyes.
We all know that we can shoot various photographs of the same scene and make it look completely different by just changing the exposure settings. For instance, if you're taking the photographs of the night sky in the Auto mode of your camera, it will come out mostly black and will be pretty much useless, but if you put the shutter speed at around 10-15 seconds and then take a photograph by keeping all other settings constant, you will get a completely different look and feel of the same night sky with greater depth and detail that you missed earlier with Auto mode. The problems with this kind of photography are obvious because if your scene has a bright object in it, it will get completely killed due to over-exposure.
Basically, if you take picture with exposure at a low setting, you'll be able to capture greater details of overly bright objects, and if you take the exposure settings to a very high level, then you'll be able to get the images of even the most dimly lit objects and here in lies the contradiction.
Personally, I liked AnandTech's review from a month ago better. If you're interested, its available here.
"This new video/gaming graphics technology is expected to debut soon with Valve's Half-Life 2: Lost Coast title."
Its okay to post old news, but Lost Coast is already out, as is DoD:S which also uses HDR.
Pain lasts, kid. Its how you know you're alive. Sometimes I think this growing up thing is just pain management-TheMaxx
http://debevec.org/ lots of info here
My wish list for Christmas 2005:
- Ending world hunger
- Finding a cure for AIDS
- Making objects brighter by allowing them to use the full brightness capabilities of the monitor
Only two more to go! Thanks, Slashdot, for bringing this to my attention!
For one thing, Lost Coast is already out, and has been since last week.
For another, the first Valve game to use HDR is DOD:Source, and that's been out quite a while already.
And finally, Valve didn't actually invent HDR, so other stuff has already used it.
I think that striving for accuracy and balance of the elements is probably more important than striving for the maximum ____ your system can deliver.
Brightness values should have NEVER been bounded above in the first place (and now that I think of it, bounded below, either). The video card should be charged with computing everthing and only then "flattening" the image into something the monitor can display. It could even add some bloom automatically. HDR and motion blur will do wonders for realism...
Quid festinatio swallonis est aetherfuga inonusti?
Africus aut Europaeus?
why, why did i get a laptop for gaming? my computer can barely render the Sims 2 - yet guild wars runs fantastically... im not getting my hopes up about running Civilization 4... and its only a year and a half old. the sad part is, my card is better than half the laptops cards out there (which have shared memory and wide-screens!).
i remember years ago, i could still play the games fine if i just turned the graphics down - but that doesnt work anymore! my GeForce 2 lasted more than 2 years, but this one barely lasted over a year!
one things for sure, i think these games need to allow more user control so I can set it at a reasonably low level, and support for widescreen. we need more flexible graphics engines before we add more insane quality/lighting effects!
After playing Half Life 2: Lost Coast with Full HDR at 1280x1024 and settings all the way at max, I came away with the impression that HDR is really quite nice. Comparing screens with normal filters and HDR, HDR is much more realistic. When you look at water reflections HDR is invaluable. Sun reflections especially looked impressive. Where normal filters made the bright spots look gray, HDR made everything shine and bleed a bit. It was quite accurate as far as the water went. Now, what I didn't think was realistic, was HDR used in the distance. There was that seem bleeding effect across open windows and such. Also, the effect is sampled every so often, I don't know what the sampling rate was there, but a couple times i noticed a slow sampling rate that wasnt entirely realistic. Towards the end of the Lost Coast level, I was impressed by the light coming in from the windows (you'll know what im talking about if you've played it). They were stained glass windows and first there was a dull light in them, but when you shot them out, a big blast of white/yellow light shines through that looks quite good. My conclusion is that HDR is good, but they should up the sampling rate in HL2LC and also change how its viewed in the distance. But what do i know... anyway, thats how i saw it.
The provided definition of HDR isn't very accurate. From Game Developer magazine's August 2005 issue:
"High Dynamic Range (HDR) rendering is a technique used to retain color precision of a rendered scene as it goes through the rendering pipeline...
For applications, especially games, this means that our scenes will be rendered in a more realistic manner in terms of lighting. Using high dynamic range rendering we can add a great deal of detail to our applications by retaining as much light information as possible. This will then cause our objects and surfaces to be displayed in a way that comes closer to resembling real life than ever before.
The problem with non-HDR games is that traditionally, the color precision of a rendered scene is lost, and the rendered display is limite to a low dynamic range of color values between 0 and 255. In the past, this limitation was mainly a result of PC or console hardware only supporting integer buffers, which has a limited range of precision when compared to floating point buffers. Thus, to perform HDR rendering we will need to render our scene to an off-screen floating-point surface, so that the data can be manipulated and made ready to be displayed on the screen."
Also, it's not Valve's technology. They've implemented it in the Source engine now, but they didn't invent it and I'm pretty sure they're not the first to use it.
Since this is a technology included in software, why is it listed as hardware?
I think, if you want to be precise, what Valve did in Lost Coast should be called Paul Debevec's High Dynamic Range.
High Dynamic Range is also a useful tool in photography, especially for digital photographers who find that the useful dynamic range of a digital camera is less than that of an equivalent film camera. Multiple-exposure bracketing can be combined with the use of special processing software in order to yield images that would be difficult to obtain with a digital camera, or sometimes even a film camera.
... designed to emulate ... lighting to closely mirror the changes we see in the real world."
Photoshop CS2 includes this technology out of the box (Photoshop CS2 HDR) -- in the demo page, notice that the sky is properly exposed as well as the vegetation on the hill in the foreground; this would be impossible to capture with many cameras. As the article linked by the original post states,
"HDR, or High Dynamic Range, is
And indeed that's what the photographic equivalent does. Unlike a camera, our eyes can properly "expose" the ground as well as they can the sky in the same scene. In fact, this is mentioned on pages 2 and 3 of the linked article in the original post.
More:
HDR - High Dynamic Range Compression - a Photoshop plugin
The Future of Digital Imaging - High Dynamic Range Photography (HDR)
Aizu University's Atrium High Dynamic Range Source Images
High dynamic range imaging - Wikipedia, the free encyclopedia
Stitched HDRI
If you would like to try this yourself, many digital cameras have a bracketing feature. I'd suggest at least five exposures, separated by one half stop or one full stop. However, it does not work well for moving objects since there will be a short amount of time that elapses between exposures.
Here is my first attempt:
High Dynamic Range Candy Corn
This particular shot was taken with a Canon EOS 1Ds MkII camera and manual bracketing, although I've made other successfull attempts with the bracketing feature of my Nikon D70.
i am a soviet space shuttle
Actually, HDR rendering has nothing to do with the contrast limits of the physical display device. Even the best display devices have limits on how bright they can get. To some extent this is a good thing, if monitors ever became capable to representing something like the sun at true brightness then we'd have to worry about in-game bugs causing eye damage by setting the display brightness too high.
HDR is a technique that uses floating point values rather than integers to represent luminance values within the pre-rendered scene. These values are then compared to each other before the scene is actually rendered and the luminance of the individual portions of the rendered scene are assigned based on the relative brightness of each light source when compared to each others. Basically, if you have a bright floodlight and a small flashlight visible to the camera the floodlight should vastly overpower the flashlight and should probably max out the brightness of the physical display device. However, if you move the camera angle up a little bit and include the sun in the scene, then HDR would dynamically darken all the other lights in order to make the sun look like the brightest light source and the sun would then have taken the highest brightness setting of the display device.
Another effect that is created using HDR is glare. An example of this in the real world is when you look directly at a bright light source, like the sun (I don't really recommend trying this out with the sun because it might cause eye damage but a flashlight or a light bulb should work too). The light source tends to look larger than it actually is because the light drowns out anything around it.
HDR rendering has been hardware accelerated on the new last few generations of video cards, but only recently has performance been acceptable enough to actually implement into a commercial game.
-GameMaster
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Looks like they apply auto-levels to each frame. That shouldn't affect performance a lot, btw. It is really a work-around for bad rendering. They could fix low dynamic range earlier in the output pipeline.
A chain is only as strong as it's weakest link.
Too bad the BrightSide display is "a little costly"... (Think several small cars -costly.)
.: Max Romantschuk
Not sure where you get that CRT figure. I have a CRT and it's actual, measured, contrast ratio is about 800:1. That's not what the manufacturer quotes (they don't quote contrast ratio), that's what an external Colourimeter measures. Also that's not driving the monitor very hard, the maximum brightness is set to about 95cd/m^2 because I find it easy on the eyes. It could do probably double that if asked to.
Believe it or not CRTs really do get good contrast and colour, better than LCDs. Many people prefer LCDs because they are often brighter by default. Just as you tend to naturally prefer something louder to something softer, you prefer something brighter to something dimmer. This goes double if the ambient lighting is high, as is usually the case in a store. You can see more low-level detail with a brighter display.
However for all that, a CRT really gets superb low-level colour detail and a much better gamut than LCDs. It's possible that the new NEC LCDs with LED backlights are better, they are at least in the same ballpark, but I've never seen one and they are like $6000 (yes, 6 grand) so it's not really a replacement at this point.
Right now, if colour and contrast is your thing, a CRT cannot be beat. $600-$650 will get you a nice LCD, either a really high-end 19" or a mid-range 20.1", something that claims 700:1 contrast witha brightness of 250cd/m^2. In reality it'll get 200 or maybe 300 to 1 at max brightness and less if you turn it down. The same money will get you a 20" (viewable, 22" spec) tube that will get 500-1000:1 contrast at a medium brightness around 100cd/m^2.
One of my friends has a Geforce 7800 GTX. Here are some screenshots of Farcry with HDR enabled.
The major part of HDR (excluding glare and all that), is that it is a way to model the way that the iris (the black bit in the middle of your eye) opens and closes at different brightness levels.
There is something missing though, which I think would be beneficial. Basically, the eye has rods and cones for luminance and colour respectively. The rods are far more sensitive than the cones, with the result being that in very low light conditions, we see in greyscale. I have never seen this effect in a game (or film), and I think it would really enhance the realism, especially in darker games like Doom3. It would be even better if the display could become slightly blurry and noisy as the rods are not as high resolution as the cones.
In a game like NFS, replicating this realistic phenomenon is difficult and nearly impossible for the lack of the ability to specify whiteness beyond level 1, but with HDR, you can accomplish just that, which is why it's important to gamers that demand realism from their games.
So you're saying that this one goes to eleven?
HDRI has been around for a long time --since the late '90's. I don't understand why this is considered new, especially since Paul Debevec introduced this at Siggraph in '99 (?) in Fiat Lux. It's been in almost all the latest big VFX movies to date. HDRI is not a "a lighting process that's been designed to emulate in-game or artificially generated lighting". It is a method of lighting scenes using real-world lighting scenarios. I suppose this is new to the video game industry, but this has been around for quite awhile, so the article is a bit misleading. For more info about HDRI, go to Paul Debevec's site: http://debevec.org/
HDR has been around for a longer while than you think. It has been used in games before, it has been demoed before. Some of you may recognize HDR in the form of light blooms, especially from the earlier screenshots of the Unreal 3 Engine, as seen here:
HDR Glow in Unreal 3
Although some say light blooms are NOT high-dynamic range (which is true for the case where you just make something radiate light in a way that washes out details of objects around it - see here), light blooms can be done with high-dynamic range color, which is what the Unreal 3 Engine page mentions in a brief caption for the above picture.
Anyways, there are other games that ALREADY do HDR, such as Far Cry (with patch 1.3 or above). The best place to get a good view of it is ON a beach in Far Cry that is directly in the sun. It is funny that Far Cry has been ignored as the first of its kind in many things, but it really did do a lot of stuff that Doom 3, Half Life 2, etc. did, except earlier. It was also virutally bugless, compared to for example, the stuttering bug common in Half Life 2. Most are misinformed in crediting games such as HL2 or D3 in bringing in the generation of shader-heavy games (aka 'next gen' games).
That being said, if you don't know what HDR is, the Anandtech Article on HL2:TLC is a good read.
> The problem I see with this is phosphor burnout.....
> running very high brightness areas on screen is going
> to seriously reduce the lifespan of crts.
So I should rather play Doom 3 than reading Slashdot on that evil white background?
There was good article on Ars Technica as well, going into a fair amount of technical detail into why Valve's HDR implementation is interesting, and why it took so long (and so many attempts) to create.
;-)
I'm still waiting for the updated Source SDK so I can build maps using HDR - it's something I'm really looking forwards to. Eat your heart out, darkness-obsessed Doom 3 and friends!
Tedious Bloggy Stuff - hooray?
Finally! I've been waiting for the day developers would decide my graphics card with its high-res 32-bit textures displayed on 1600 by 1200 with maximum draw distance, 3 kinds of filtering, and 8 layers of model mesh effects would look better washed out anytime the sun is up.
I can see it now- Unreal Tournament 2007: Pre-Order and get a FREE pair of Eagle-Eye sunglasses using patented NASA anti-glare technology!
Just give me the damn Kryptonite fog already. Serves us right for letting game designers use that much texture memory for crap like sand anyway. What did we think we were supporting?
Anyone wanna play Duke Nukem 3D? Now THAT game had some good graphics.
Or some MultiTheftAuto VC before the HDR-compatible windshield glare updates?
It's more like the situation with CDs
I'd have to disagree with you about that.
CD-quality audio gets pretty close to the limits of what the average person can hear. It's not perfect, but as you say it meets the "good enough" threshold.
Current display technology doesn't. Look at this representation of what's lost with sRGB. See what a tiny portion of green colours (which our eyes are most sensitive to!) in particular are represented?
I went to a concert a few months ago (Dead Can Dance) and their stage lighting used the full range of colours that are outside the ability of sRGB to depict. It really made me realize how much we're missing.
"...always new atoms but always doing the same dance, remembering what the dance was yesterday." -Richard Feynman
HDR is no more a hack than showing natural video on a TV. Sure, the screen has less dynamic range than reality, and you need a mapping function (exposure settings when working with natural light) to display it in a sensible way, but it still pays off hugely to do all the lighting in the scene without regard for that, just as reality dioes.
The alternative (the traditional 8-bit path) corresponds to a reality where no light can be brighter than the white of the monitor", including when adding up light from several sources! Trying to get real photorealism that way is a lost cause. There's a reason why even holywood CG until recently always looked really 'flat', except in very dark scenes (lower dynamic range to model)
And for the record: those blooming effects are not part of HDR. They are simply post-process SFX, emulating scattering and other effects in the eye and in cameras. Sure, you couldn't do them really well without HDR, so they're a nice poster child for what it lets you do. But they are not what makes the process HDR.
Volumetric effects are of course not inherently HDR either; they've eben around a long time, just too heavy to do for most games to bother with until now, and looking much better with HDR (and bloom).
sudo ergo sum
That is the worst explenation of HDR I have ever seen. Clearly missed the point.
sudo ergo sum
"HDR allows you to make the objects brighter by allowing them to use the full brightness capabilities of the monitor."
Pretty bad lie. By using a #ffffff color you already "use the full brightness capabilities of the monitor", unless you count turning up the brightness setting in yout monitor. As it has already been said, it lets the objects be brighter in the internal calculations, not on the monitor.
Either HDR is a bunch of crap or the explanation is. I'm reminded of Nigel of Spinal Tap explaining how his amp is better because it goes to eleven.
I hate to be "one of those people" but this article sucks - four really short pages and not a single screenshot - WTF?!? If you want to *see* Valve's HDR, you'll do no better than bit-tech's series of articles:
Half Life 2: Lost Coast HDR overview
Half-Life 2: Lost Coast review
Half-Life 2: Lost Coast Benchmarks
Day of Defeat: Source review
Another article about HDR that doesnt actually explain what is really is. It starts off ok but then falls appart. Bloom isnt HRD, Exposure control isnt HDR, Radiosity isnt HDR...whats more all of things are possible in LDR (though exposure control is a bit difficult). HDR just makes everything more realistic. The stuff about the contrast ratio of displays. The final contrast ratio of the image isnt what HDR is about either. The it will be important with newer monitors. I mean a LDR image has a contrast ration of 256:1...whats the contrast ratio of a normal CRT? LOL, if that was so important...whats the point of downloading normal JPEG previews of loast coast? Its articles like this are what make people say "WOW..another game with specular bloom...not worth a $400 graphics card". I am getting tired of reading these articles that attempt to 'dumb down' these subjects for us everyday gamers...the trouble is, most of the time theyre totally misinformed. I remember when HDR first became known (to gamers: its already known to 3D artists), most magazines explained how it was a way of displaying ever more colours and that our current 32 bit systems dont display enough colours to be realistic. Though that might be true its not what HDR is. The most basic flaw in these articles is that HDR isnt just lighting. HDR makes EVERY aspect of the games graphics more realistic (or has the potential to). Bloom, motion blur, global illumination (once its implemented in games), fogging, reflections, depth of field, ambient occlusion (once its implemented in games), transparency all become more realistic in a HDR engine. Thats before you even concider the contrast ratio of the monitor.
As very many have already pointed out, that was indeed a crap article. I don't want to spend any time quoting it and going "WTF?!", but I *do* want to link to OpenEXR, which is a file format for managing HDR images. It typically uses 16-bit floating point numbers per pixel, which seems to give a decent brightness range. It's cool to watch the same image rendered using different levels of "virtual exposure". It's by Industrial Light and Magic, which some of you might have heard of. I have, of course, no affiliation with either, just wanted to link to something relevant.
main(O){10<putchar(4^--O?77-(15&5128 >>4*O):10)&&main(2+O);}
Paul Debevec, through his papers on acquiring low dynamic range imagery and turning that into high dynamic range imagery - and a utility to go with it coded with help from others; HDRshop, has made HDR accessible and popular.
However, 'HDR' as the storage format being used most frequently already existed in the rendering application Radiance for a long, long time before that.
In fact, -most- rendering applications render in HDR - but are forced to clip values so that you can actually output it to a regular display (e.g. your TFT) or storage format (e.g. JPG).
In fact, Valve's HDR isn't an HDR display technology. It's a partial HDR pipeline for rendering (making sure that glints of the sun are bright on water surfaces, and not dull), processing (bloom effects) and simple tone mapping a la a LUT (look into a room from a skylit outside, and the room may appear dark. Walk inside, and the room appears normal whilst the outside world will appear very bright indeed. Note that a more proper tone mapping algorithm would, besides being computationally very expensive, show the room normally and the outside world bright - but not so bright as to be blown out.)
Once we've all got HDR displays (search on Slashdot for these - I've seen them, they're awesome), we can do away with all these basic gimmicks as the human visual perceptance system will simply do all the interpreting of what should be 'correct' HDR values coming from the display.
for more bits per color channel. 8 bits is clearly not enough. 12 bits (linear) is almost, but not quite enough to represent what film can, or what the human eye can see. 16 bits is enough. But not for everything...
A seond use for more bits is various image based rendering techniques. For these, 16 bits is often not enough, unless you go floating point -- and even then, 32 bit floats will produce better results. These techniques often use "blacker than black" (negative values) and "whiter than white" (values > 1.0) as intermediate results of calculations.
As a side note lamenting the demise/withering into obscurity of a once great company, starting around 1992 with the reality engine, SGI made graphics pipelines with 12 bit/channel RGBA support from end to end. It is only recently that we see support for more than 8 bits/channel in the pc world.
Ian Ameline
I'm sure /.'ers know full well the effects of HDR in those rare occasions that we actually venture outside into the sun.
I think that technologies like this being refined are really where the future of gaming graphics is going to be for a while. While there is still a ways to go in terms of polygon count, texture and bump mapping, etc, a lot of progress has been made in these areas. I think what we will see (or hope to see anyway) offered in newer games is more support for technologies that simulate real time lighting, shadows, translucance, refraction, etc. A large part of this I think is that there are only so many resources that can be dedicated to artists now to create higher polygon count models and higher resolution more diverse textures, so things that can be done to increase the visuals of a game without having to dedicate significantly more resources to artists can vastly improve the visual quality of a game without such a significant increase in cost associated with actually crafting those visuals. With technologies such as this allowing a more realistic rendering of ourdoor scenes combined with improving algorithms for creating outdoor environments and the ability to create fractal plantlife I think that we will see a new generation of games that take the player more and more often into the less confined feeling outdoor world.
Famous Last Words: "hmm...wikipedia says it's edible"
You know, it masquraded as a good review, until I read stupid-assed commentary like this:
Here, we see how the bloom effect starts to put a strain on the lower memory cards. The X800 and, in particular, the 6600 GT are the most memory-limited of these cards, but ATI's X800 does significantly better than the 6600 GT.
Welcome to Video Rendering 101. Tell me class, which card will be faster, and by how much:
The 12-pipe, 400 MHz core clock card (x800), or the 8-pipe, 500 MHz core card (6600 GT).
This isn't hard. The x800, when core-limited, should produce speeds 20% faster than the 6600 GT...and lord almighty, it's a miracle: the x800 is 20% faster than the 6600 GT with full HDR enabled! It must be the EXTRA 128MB RAM, or the 40% FASTER MEMORY SUBSYSTEM. It couldn't be the damn raw pixel processing power advantage.
And now class, why would the lower-end cards in this test show greater performance loss? Is it because Here, we see how the bloom effect starts to put a strain on the lower memory cards.
HELL NO.
It's called CPU-LIMITED. You can't measure true relative performance drops becuase the scene is CPU-limited to approximately 70fps. The 6600 GT is not even able to reach the 70fps mark without HDR, and suffers noticably with it on. The other cards scale as you would expect them to according to raw core clock speed, once you turn up the pixel processing requirements (full HDR), and the 7800 GTX is STILL CPU-limited.
And then, after mentioning it CLEARLY in the breakdown above that Valve's HDR implementation supports FSAA, AND after seeing plain-as-day that the 7800 GTX is still CPU-limited, the author doesn't try out FSAA performance. A 5-year old could write the same review.
I wouldn't be surprised at all if most of the language and pictures are verbatim from a Valve-supplied press pack.
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