For Your Information: Installing Games with DirectX on Steam

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This is a new segment that I'm calling "For Your Information". What I hope to provide with this is insight into some of the most common questions and concerns associated with Steam or its games. The information I give will be coming straight from Valve via the Steampowered User Forums, because these sources are easy to digest and readily available. Developers and other employees from Valve are always responding to your questions, but unfortunately a lot of this information is quickly buried under an avalanche of other posts.
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Today's topic is DirectX installations. You know, usually when you run a DirectX game through Steam for the first time, you are greeted with yet another DX installer. Well contrary to popular belief, the reason for this isn't to cause you grief. Apparently it has something to do with Microsoft's D3DX library.
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According to John McCaskey, a software engineer for Valve, it's all about version control. There are many versions of the D3DX library for Direct3D 9, 10, and 11. A lot of games use this library on top of Direct3D to utilize additional graphics functionality.

Each game that uses the D3DX helper library is linked to a specific version. As such the game must run the correct D3D installer version that it was specifically compiled with to ensure the binaries exist.

Even if you have some of the most recent versions of the binaries, that does not guarantee that you have all of the other necessary binaries that a game might require to run. Just as well, having the correct files already installed for the x86 platform may not be enough. A particular game that supports x64 will need to run the exact DirectX installer again, but this time it has to target a different platform...

Furthermore, Microsoft's licensing terms prevent anyone from distributing the files directly, the only way to distribute them is to run the installer, that's also the only supported method from Microsoft to check that the correct version installed.
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Games which don't use the D3DX helpers (such as Source engine games) don't require running the annoying installer on first launch as they only depend on major d3d9/10/11 versions being installed.

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So in conclusion, you might often find yourself face-to-face with the DirectX installer, but that's not totally Steam, or a game developers, fault. It comes down to Microsoft's redistribution licensing terms with the D3DX library and the packaging framework. John McCaskey says that Steam could be a little bit smarter by matching already downloaded installers on a machine to a games required installer so that the content can be shared, instead of having to be downloaded again, but the tradeoff would be marginal.
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John explains this better than I ever could, so head on over to SPUF to read his entire response!

 

[ríomhaire]

Thanks for this. Good to know why I need to install DX seven hundred times.

 

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No problem!

 

[Blindasabat]

Like Riomhaire said.

 

[Hectic Glenn]

I always put it down to the stupidity of Windows not realising it was already installed and just put up with inconvenience.

 

[Dandan]

since I got my new laptop I've installed roughly 20 games on Steam now and every time it says installing DXversion?? and now it all makes sense. I noticed it too on my PC but more so on my laptop.

 

[DEATHMASTER]

Knew about this but nonetheless a little strange to see everytime I get a new game.

 

[Avoidist]

Glad to finally see an explanation for this, always frustrated me a bit.