Half-Life 2 HDR -- Why?

#1 Yeah, maybe it is my setup or my eyes or something, but I really can't see enough of a difference iwth HDR to go "Wow!".

Sure it tweaks the brightness etc, but I don't fell like I'm seeing a whole lot more.

I'm sure it is cool, but I don't see it.

#2 The thing that's special about Half Life 2's HDR, and HDR in general, is it's a way to simulate the higher ranges of light on your monitor.
When you see things with your eye in real life, there's a massive range of possible light levels that you eye can see, although you can only see part of it at a time. What HDR allows you to do is simulate going into the greater ranges, even though your computer monitor doesnt allow it. Most of this effect is acheived by "blooming" which is used to simulate the higher ranges on your computer monitor. With your real eye, you wouldn't actually see any bloom unless you're looking dead on at a light source or a surface that's reflective enough to shine the lightsource into your eye(such as metal or glass)
The biggest problem with trying to simulate this effect on your computer is your monitor doesnt support the ability to go into the higher ranges, because it can only emit light so bright. So, instead, we use bloom to show that it is indeed a really bright surface.

The deal with the transitions of lighting levels is the way your iris works. You've walked from inside to outdoors, and have gotten that overbright, blinding effect(though sans the massive blooming ;) ), this is another aspect of HDR.
The reason we use the transition, is because your eye is only capable of viewing a specific range of light at any given time, so to allow you to see a greater range, your iris will adjust, allow you to see the lower, or higher levels of light, as though it where normal.
The reason we do this ingame is to allow us to see the greater range of light as well.
Would it be nearly as appealing to walk around ingame looking at nothing but bloom? Probably not. So the game adjusts the apature of the camera to simulate the way the iris works.

HDR's spiffy because it allows you to simulate the way an eye works, and simulates a huge range of lighting, even though your monitor doesnt actually support it.

So why the massive FPS drop? It likely has to do with the approach to doing the HDR. "True" HDR implemention generally requires several steps, alot of which are grabbing the screen and doing post processing. Depending on what all your attempting to acheive, you can end up grabbing the screen many times, and that ends up being a big drain on your poor computer. Other implementations likely dont need this approach, or nearly to that degree(such as mitten's HDR implementation for ps1.1).

Hope you guys found this a bit helpful. :)

#3 I found the articles on Valves approach to HDR very interesting (they are all over many websites), but I don't have too much actual interest in the expansion even as an owner of HL2.

I was more interested in the tech for tech's sake cool factor. It does add a fair bit of life to a scene, but hardly essential for any but the games that rely on pushing the cutting edge of graphics.

edit: typo

#4 "but hardly essential for any but the games that rely on pushing the cutting edge of graphics."

If it's done well it could really add depth to a scene and even the gameplay. It's not really about graphics as it doesn't add any essental *visual* aspect that can't already be simulated - to a degree. What I think is important is that it opens up any extra element of interactivity. Well, make it easier to simulate an effect that can be translauted into gameplay of some kind. For instance, a game that relies on stealth - if your character has been in a brightly lit area and gets discovered it will be more challanging to run out into the dark (assuming it's night time) but can't see squat right away untill his eyes adjust - could make finding a decent hiding spot kinda tense. It would also be good for horror games or games where you need to search for objects which you'd only find if in dark/bright places once your eyes adjusted.

It will also hopefully remove the need for games to stop simulating the sun as being overly blinding unless you've just steped out into the light - and possibly provide the even more annoying effect of having everything be washed out after you look at the sun. It could also breathe new life into tatical shooters with decent flash bangs effects for once. Oh and the nasty combination of using light amp (NV) goglles and coping a flash bang - NV and other such visual effects could also be simulated a lot more releastically as well I'd assume.

Not to mention it will be easier to impliment bloom like effects. The first kind of bloom effects took anything and everything that was bright (and often even the things that weren't bright at all) and blurred it all over the screen, now we can simply set the brightness of an object and let the HDR take care of blooming only the parts of a scene that are "over bright". No more glowing white tee-shirts or glowing skin like the "someone just rubbed salt into my eyes" bloom effects in Deus Ex 2.

#5
oh... so nice!

#6 WOW!!!
I havent had a chance to play with it yet as Ive been busy the las to days... but OMG. Those screens look great. The guys at valve continue to blow me away.

#7 Thx for the pics JimOMighty... yeah, i could see where this could be used
to enhance a scene... or overused to destroy one...

overall though... i think it's a plus...

--Mike

#8 HDR is the shit! I don't know how anyone can yawn at this? This not only looks better and more realistic but it also is far more immersive. Anyone with any appreciation for photography should be very excited about HDR. It gets you closer and closer to the real thing.

#9 I plan on implementing the technique in my game. I think it adds a lot to the look and feel of a scene. I haven't experienced bad frame rates, but then again I am running with an AMD FX57 and a nVidia 7800 card! ;)

#10 To me, HDR, just seems too much like cordinated bloom (Which if i understood Jeff right it is). Not all that special to me sorry. Sure it looks good, but is it worth a 20 FPS Drop, and barely being able to play the game?

#11 I haven't had a chance to download the new level yet, but the technology looks impressive. I think improvements in lighting should always be a high priority for game engine developers because everything we see is based on light. For now I do not think the tech will be useful in fast paced action fps games, but it would be nice in slower paced stealth games, RPGs, or MMOs.

Here is a link to a description of HDR I recently read.
www.anandtech.com/video/showdoc.aspx?i=2545

"The 'dynamic range' of a scene is the contrast ratio between its brightest and darkest parts. A plate of evenly-lit mashed potatoes outside on a cloudy day is low-dynamic range. The interior of an ornate cathedral with light streaming in through its stained-glass windows is high dynamic range. In fact, any scene in which the light sources can be seen directly is high dynamic range." - Paul Debevec

#12 Lost Coast is a joke. Touted as a tech demo, pffft. Its broken, unimpressive, and SOOOOO Last year :P

#13 Would it be better if HL2 used ACTUAL shaders to produce HDR? I mean would there be a performance gain?

#14 Chris: Noone except the coders at Valve can answer that. Either way, the Source HDR is freaking awesome IMO. Day of Defeat Source uses it and I think it makes the game play a hell of alot better with it.

#15 Downloading Day of Defeat Source. :) Thanks for the heads up Josh.

#16 It may look better, but as i think as alot of people (atleast indie's) have in the back of their head. COULD IT BE BETTER? This is more research for me, for when i get TSE< and look into HDR.

#17 Chris the bloom is just a way to present the HDR. You dont see the HDR itself directly, infact you cant. You have to think past the bloom and the tone-mapping and think what the handling of the high range of values could be used for, not limited to the way its used here (although that is how most people implemented HDR into their engine, including me).

#18 THe bloom is only used to simulate overbright white. The Source HDR actualy does more than that, even if some of you cannot see it. IMO, Source with HDR makes it look about 10x better, just because the seeminly higher range of colors it produces(read: more detail). Also, the bloom in the sky is VERY realisitic, I observered the exact same type of blooming out of my backdoor ealier today.

Dod:Source images:






Can you tell I like to snipe?


Edit: Take a good look at Jim's screenshot of the Fisherman's face, you should beable to clearly see the amount of color detail brought out in his face that wouldn't be there without HDR.

Too bad HL2 didn't have it...

#19 They should add to it CS : Source... Shouldnt be too hard.

#20 HDR is a very nice technology. I think some may be disappointed because it does not correctly simulate what the human eye sees in real life and sometimes does the opposite to what you expect. Perhaps FPS isn't allways the best genre to show it off with. Reason being that HDR more acurately simulates what a camera sees, where the human eye is far more versatile and complex and more adaptable to pretty extreme changes in lighting.

All the same, the effect is a huge plus, and when combined with GI lightmaps in the scenerly like HL supports, when combined with the HDR you do get a far more realistic lit environment that does make the game a lot more realistc and a lot more advanced than simple bloom and 2Xmodulate blendmodes that have become quite common of late.