Developing a game with OpenGL, which OpenGL version would have no problem running on most computers? For both Hardware and Platform (PC/MAC/LINUX).

Any feedback would be helpful, thanks

One possible advantage of using an older version is that older codepaths are more likely to be very well supported. One possible disadvantage is that these older codepaths may not have recieved more recent bugfixes or performance improvements. As always it's a balancing act.

A possibly useful tip may be to look at what reasonably recent OpenGL games do, and copy that. You can use a tool like GLIntercept to peek under the covers, look at what calls they make, what versions they use, and get a reasonably decent idea of how things are structured. The thinking behind this is that hardware vendors are more likely to optimize around (and provide more robust code paths for) popular OpenGL games, so by using the same calls you're going to be hitting driver codepaths that can be assumed to be reasonably decent.

Of course, the counterargument to this is that a game may be doing something dreadful that a driver needs to implement a workaround for, but at least it's a starting point, so maybe grab the latest id Software games and one or two other titles and have a look.

That aside I'd personaly be inclined to shoot for GL3.x and pull in as much later functionality via extensions and as alternate codepaths (where those extensions are available) as possible. Since you're starting out here you're looking at maybe a year or so before you've something solid done, by which time things will have moved on from where they're currently at. But this all depends on your target audience and only you can define that.

So the target audience? Key questions would be what type of player you're aiming for? Casual? Hardcore? Somewhere inbetween? Do you want to hit laptops, business-class PCs and el-cheapo "multimedia" PCs? How much support are you prepared to offer? Because face it - you're never going to hit "most PCs" for the simple reason that "most PCs" includes a hell of a lot of - frankly - f--king awful things infested with cruddy startup apps and which haven't seen a driver update since the day they came out of the factory. So trim that one down - if you can get a 10% to 25% coverage but if that coverage includes 95% of your target audience you're doing OK.

A final tip - the fact that you're asking this suggests that this stuff is relatively new to you. If that's the case, then maybe back off on the multiplatform ambitions for now - you've enough to be getting on with learning without having to deal with the vagaries of 3 different platforms too. You can always pick it up a little later once you get more confident.

I've seen quite a few projects start like this. "Which is the best OGL for compatibility?" And they land on OpenGL 2.1.

It is true, pretty much anything you grab will support OGL 2.1 (grab a can on the street, it supports 2.1). The thing is that I've seen projects like this going on for years, while OGL 2.1 was a good idea 3 or 4 years ago, compatibility wise, today? When their game hits the street? Not so much.

So I'd pick up something from OpenGL 3.0 and upwards.

Also, many of them feel that updating drivers is a difficult thing to do (too technical for them) and are afraid that they will mess up their system.

Honestly, this has mainly to do with one of the most common recommendations to install drivers, which is to go to safe mode, uninstall the old driver and install the new one. You don't have to, but it isn't hard to see where the issue lies. Besides, people think that if it already works as-is it's probably fine, not realizing that old drivers may be leaving features unused (e.g. the drivers bundled with the GeForce 7 use OpenGL 2.0, but the newest drivers provide OpenGL 2.1).

In reality, there are a lot more games that use DirectX than use OpenGL (easily 10 to 1 ratio). So, Intel/AMD/NVidia have not had too much incentive to keep the quality of their OpenGL drivers on par with the quality of their DirectX driver. But, the quality of the OpenGL drivers in the past few years has greatly improved.

It's a chicken-and-egg situation, if nobody uses OpenGL, there's no incentive to improve its support, which in turn means nobody wants to use it, and... well, it's a self-feedback loop. I think id is pretty much the only reason it didn't die completely. At least OpenGL 3 seemed to have gotten all vendors back into OpenGL, just because apparently it had enough of a reputation to make lack of support look stupid (maybe the backslash when Vista was implied to lack OpenGL support was a hint, even if it turned out to be false later).

The bad news is that a lot of people are still using (or stuck with) older, buggy OpenGL drivers.

I wouldn't expect those to care about gaming anyway ^^; (or to have something that supports anything newer than 1.1 for that very reason...)

EDIT: basically, if you care about people with old systems (especially people in e.g. developing countries, where hardware can be considered quite expensive), OpenGL 2 may be a good compromise. If you expect some decent hardware, OpenGL 3 would be better. I'd say that OpenGL 4 would be better if considered optional for now unless you really need the most powerful hardware (i.e. support it if you want but don't assume it'll be very common).

If somebody is stuck with OpenGL 1 that's most likely the kind of people you wouldn't want to bother targetting anyway... Either their hardware is pretty weak and will slow down without much effort or they're the kind of people who'd rather stick to browser games (if they play games at all).

The bad news is that a lot of people are still using (or stuck with) older, buggy OpenGL drivers.

I wouldn't expect those to care about gaming anyway ^^; (or to have something that supports anything newer than 1.1 for that very reason...)

You would be surprised. Check out the Steam or Bethesda forums for Rage - there was an awful lot of so-called "hardcore gamers" who had issues because they never bothered updating their drivers, not to mention an awful lot more who had issues because they were randomly copying individual DLL files all over their systems without any clear knowledge of what they were doing. (It's also a good example of how poor driver support can mess up a game.)

Many thanks for the feedback everyone.

Turns out this is the ugly part of game dev, hopefully pumping up the system requirements and some proper error handling, will make people aware of what they need.

I'm targeting people with decent computers, something that can render 3D graphics with post processing at a playable fps, I really REALLY want to avoid the old pipeline, it's just seems dirty, do some newer AAA games even use old pipeline these day?

For example I am interested to know what versions of OGL do Valve use for their games on MAC?

And I'll probably just end up going with 3.2. seems to be a better choice.