Is there any advantage to using C++ instead of C# when using Direct3D?

Question

Is there any advantage to using C++ instead of C# when using Direct3D? The tutorials I've found for C++ and DirectX all use Direct3D (which to my knowledge is managed). Similarly, all of the C# tutorials I've found are for Direct3D.

Is Direct3D managed? Is there any difference between using D3D in either of the two languages?

Answer 1

DirectX is entirely native. Any impression you may have that it's managed is completely and utterly wrong. There are managed wrappers that will allow you to use DirectX from managed code. In addition, DirectX is programmed to be accessed from C++ or C, or similar languages. If you look at the SlimDX project, they encountered numerous issues, especially due to resource collection, because C# doesn't genuinely support non-memory resources being automatically collected and using doesn't cut the mustard. In addition, game programming can be very CPU-intensive, and often, the additional performance lost by using a managed language is untenable, and virtually all existing supporting libraries are for C or C++.

If you want to make a small game, or something like that, there's nothing at all stopping you from using managed code. However, I know of no commercial games that actually take this route.

Answer 2

The point of Direct3D is to move rendering off the CPU and onto the GPU. If there were to be a significant performance difference it would be for that code that runs on the CPU. Therefore I don't see that there should be any significant performance difference between native and managed code for the part of your code that interfaces with Direct3D.

Direct3D itself is not managed code.

Answer 3

It depends on what you're doing exactly. As David Heffernan mentioned, one of the objectives of Direct3D is to move as much processing as possible to the GPU. With the advent of vertex shaders, pixel shaders, and much more, we're closer to that reality than ever.

Of course given infinite time and resources, you can usually create more efficient algorithms in C++ than C#. This will affect performance at the CPU level. Today, processing that is not graphics related is still mostly done on the CPU. There are things like CUDA, OpenCL, and even future versions of DirectX which will open up possibilities of moving any parallel-friendly algorithm to the GPU as well. But the adoption rate of those technologies (and the video cards that support it) isn't exactly mainstream just yet.

So what types of CPU-intensive algorithms should you consider C++ for?

• Artificial Intelligence
• Particle engines / n-body simulations
• Fast Fourier transform

Those are just the first things I can think of. At least the first two are very common in games today. AI is often done in a compromised fashion in games to run as quickly as possible, simply because it can be so processor intensive. And then particle engines are everywhere.