Bloom vs. HDR (not game specific)

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eddieck

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Taking Source games (at least TF2 and L4D2) as an example, they offer both "full" HDR and bloom. BC2 also offers bloom. Oblivion offers the same as Source games.

What's the actual technical difference? My current understanding is that bloom is a "fake" HDR effect and full HDR is obviously the real thing but I'm not sure if that's correct. In any case, it simulates an artifact of cameras, right? In an FPS you're looking through the eyes of a soldier, not a camera lens, so it seems kind of retarded.
 
Yeah HDR uses fancy algorithms and shit to dynamically simulate ambient light in a "realistic" way (I've never seen light behave the way it does in hdr lighting in real life, but whatever).

Bloom just fakes it.

They both look shit imho.
 
Thought hdr was like if you where to sit in a dark room and walk outside, before your eyes adjust, everything would seem very bright or walk into a dark room and you cant see well and everything is to dark until your eyes adjust. So, for fps, it does make sense. Unless im thinking wrong about what hdr is. A simulation for your eyes adjusting to light or darkness.
 
SubyJay said:
Thought hdr was like if you where to sit in a dark room and walk outside, before your eyes adjust, everything would seem very bright or walk into a dark room and you cant see well and everything is to dark until your eyes adjust. So, for fps, it does make sense. Unless im thinking wrong about what hdr is. A simulation for your eyes adjusting to light or darkness.
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Actually what you describe is a histogram function. HDR basically takes the linear RGB spectrum (-1.0f to +1.0f) and attempts to map the non-linear human visual response to it, in order to get a more realistic look.
 
Understood now. However, quoting the Wiki link provided: (I tend not to use Wiki as a source for most things, but I'll assume this is accurate)

Bloom (sometimes referred to as light bloom or glow) is a computer graphics effect used in computer games, demos and high dynamic range rendering (HDR) to reproduce an imaging artifact of real-world cameras.
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In an FPS you are seeing through the eyes of a soldier, not through the lens of a camera. It would seem to me it's not very realisic, or am I missing something?
 
Sometimes if you're eyes are wet enough, bloom can occur when a light is very bright & shining at an angle. I know I've seen it with my glasses as well as contacts...

HL2 has Gordon Freeman who is a glasses wearer after all...
 
eddieck said:
Understood now. However, quoting the Wiki link provided: (I tend not to use Wiki as a source for most things, but I'll assume this is accurate)



In an FPS you are seeing through the eyes of a soldier, not through the lens of a camera. It would seem to me it's not very realisic, or am I missing something?
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It's an artistic decision, i guess.
 
HDR is just an improvement in the range of colours/brightness that can be used in the scene, it's a greater number of discreet steps between the darkest and lightest portions of the screen, without HDR you get colour banding in scenes that have both very dark and very light areas visible at the same time.

Bloom is an effect used to mimic an effect of cameras where bright areas can essentially bleed around geometry. Bloom doesn't need HDR as far as I know but it looks a hell of a lot better with it, since bloom is most noticeable where a bright light source is bleeding around the edge of dark geometry and you have a very large contrast range in the scene.
 
SubyJay said:
Thought hdr was like if you where to sit in a dark room and walk outside, before your eyes adjust, everything would seem very bright or walk into a dark room and you cant see well and everything is to dark until your eyes adjust. So, for fps, it does make sense. Unless im thinking wrong about what hdr is. A simulation for your eyes adjusting to light or darkness.
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Yes. But it's not really trying to mimic human vision , it's just trying to achieve the same result (to display dark or bright scenes with a wider range of colours).

Clearly, you could do this without applying any sort of bloom effect, so the two are largely independent. The reason they tend to go hand in hand is that HDR allows you to do bloom a whole lot better. Working with a wider range of colour values means you can distinguish a white light from a white person, so you can make light bleed from one and not the other. Traditional post-processing bloom can't tell the difference, which is why you get people walking around glowing like fluoro tubes.
 
eddieck said:
In an FPS you are seeing through the eyes of a soldier, not through the lens of a camera.
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That's also why I think film grain is a bit pointless in games. You're supposed to be seeing the scene first-hand, not watching an 8mm movie of the scene.

Ultimately hdr is necessary to simulate realistic lighting. Whether or not the engine manages to is another story.
 
Go grab that free HL2 Lost Coast level...has walk throughs on what HDR is. Neat little level, very cool explanation of everything.
 
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