Slashdot Mirror
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.'"
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?
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.
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
Rules of Conduct:
#1 - The DM is always right.
#2 - If the DM is wrong, see rule #1
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?
> 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?
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.
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.
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.
Man is the animal that laughs.
And occasionally whores for Karma.