[.net] C# Renderloop

Out of random, I just stumbled upon this page...

http://www.csharp-home.com/index/tiki-read_article.php?articleId=146&page=2

... it looks pretty promising, so if no better (managed) loop is known, I'll use it. [smile]

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Original post by Thevenin ... it looks pretty promising, so if no better (managed) loop is known, I'll use it. [smile]

I use a loop very similar to this. Some people poopoo on this loop because they claim it has some kind of interesting memory allocation characteristics that they do not like, as if they never render any memory in other parts of their engine. I call BS on this argument, but to each his own you know... they can run whatever loop they want. :-)

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Original post by krum I call BS on this argument, but to each his own you know... they can run whatever loop they want. :-)

Unfortunately you are utterly wrong so you shouldn't "call BS on this argument". Using DoEvents is the worst possible way to have a renderloop in C# because of all the needless allocations and generations getting bumped in the GC. Although I do want to add that until you actually see this being a problem (which you will in a larger game).. who cares? I say use DoEvents and later on down the road if you profile and find you have a problem you can refactor it.

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Original post by Saruman Unfortunately you are utterly wrong

Wrong about what? It does not appear to me that I made any specific statement to be wrong about.

Apprarently DoEvents makes several managed allocations. Basically, this means that the garbage collector fires more often than it would otherwise. Microsoft claims that a generation 0 garbage collection (which is where the DoEvents allocations would be collected) has a performance hit about equal to a cache miss, so this should be nearly unnoticable, at least until you are pushing the limits of what your machine can do.

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Original post by krum Wrong about what? It does not appear to me that I made any specific statement to be wrong about.

When you said "I call BS on this argument". I was just letting you know that it is in no way "BS" and there are memory allocation issues regarding the generational GC.

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Original post by Thevenin I need a managed (no dllimports/win32 dependencies/etc) render loop for my C# application. Any ideas where I can find one? Or do any of you know of a good one?

Why don't you just use the one that microsoft uses in the latest DX SDK?
There's probably some pretty good reasons for using it.
If not you can dig up and older DX SDK and use the old way microsoft used to do it using doevents.

I don't think there is any (if I'm wrong, someone please tell me).
The way the DX framework does it is by doing a P/Invoke to call the Win32 PeekMessage function. This tells you whether or not there are messages waiting, and if there are, then a DoEvents call is necessary. Otherwise, you can skip the DoEvents call and save a bit on memory and time.

You should read this if you don't already know about it:
My opinion, and as with all free advice you get what you pay for, is that for the kind of projects most of us are working on it really doesn't matter. Pick one and go with it. The memory allocations with .DoEvents are high but its all going to be generation 0 garabage collected anyway, you are much more likely to screw up something in your own code that causes worse memory issues. As for the increased framerate - unless you are a computer graphics genius there are likely to be algorithmic issues to do with your rendering that will dwarf the effect that the render loop has.

I've always been a fan of the OnPaint() event handler method. You put your game loop inside an override of your Form's OnPaint method, then call this.Invalidate() at the end of the loop right away. A lot of people feel its hackish and ugly, but it gets the job done and I think it actually makes some logical sense going in the OnPaint method. It doesn't have the memory overhead of the DoEvents method.

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Original post by Etherstar I've always been a fan of the OnPaint() event handler method. You put your game loop inside an override of your Form's OnPaint method, then call this.Invalidate() at the end of the loop right away. A lot of people feel its hackish and ugly, but it gets the job done and I think it actually makes some logical sense going in the OnPaint method. It doesn't have the memory overhead of the DoEvents method.

That's the way they do it on the ms coding for fun website here:
This might explain one reason why games almost always use 100% of your CPU even if they don't appear to be doing much. The faster your computer is, the faster this loop will run and the smoother the animation and the synchronization will be.

There is one slight problem with running a tight loop like that, at least in Windows. If you don't allow Windows to check for and process Windows messages and events, your application will be marked as "Not responding" by the operating system. You might have seen this in your applications if you have a loop that runs for a long time. You might also have solved it by putting a call to DoEvents into the loop, which allows Windows to process the events. This can work reasonably well if you know the loop will end eventually, but in this case the loop is the entire game and you need a better way.

The method I have chosen to use for these games is NOT the most efficient (for a full discussion on this under Managed DirectX see the MDX Game Loop FAQ), but it is the simplest, and none of the games covered here needs the more complex method.

I'm using DoEvents() and i cant notice that it is slow. In a big game you have hundreds or thousands of allocations each frame, and a GC run almost each frame. I dont think DoEvents() makes any difference.

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Original post by cody I dont think DoEvents() makes any difference.

Depends on the game.

http://blogs.msdn.com/tmiller/archive/2005/05/05/415008.aspx

I was going to post Millers loops - but they do the whole dllimport thing - something the OP didn't want to do.

Well, a small game is fast enough anyway, even with DoEvents(). A large game has so many allocations that DoEvents() is no bottleneck.

I think its a micro-optimization that you can do if you have nothing else to do. Its not wrong to do it, but its wrong to say it is necessary for a game or it will be slow.

Why not throw a "while(!done){ //game loop code }" into a seperate Thread?

Ricks discussion on different approaches

Ricks Ideal 100% Managed Loop

Benchmarks of different loops

I wonder if there is a better 100% managed loop out there waiting to be discovered yet. Though as it was Tom and Ricks jobs for a while to hunt out such things... I dunno, seems doubtful.

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I've read Rick's blogs on the subject a couple times now, and I still don't believe his solutions are 'Managed'.

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Original post by paulecoyote I was going to post Millers loops - but they do the whole dllimport thing - something the OP didn't want to do.

Likewise.

I'm just not sure if there's a completely managed render loop that really performs well.