DirectX or OpenGL [closed]

Question

If you were writing the next 3d graphics intensive application in C# (like a 3d modelling and animation software), which one would be a better choice?

If we consider C# as platform independent, then OpenGL seems tempting, but what about the performance, etc?

Since the used language is C#, the performance is pretty crucial to consider.

Edit: You can also consider SlimDX and TAO, OpenTK, csGL, etc too.

Answer 1

Performance in managed code, with respect to the graphics subsystem, is not bad. SlimDX pays a slightly penalty over completely native code on each call into DirectX, but it is by no means severe. The actual penalty depends on the call -- a call into DrawPrimitive will be vastly more expensive overall than a call to SetRenderState, so percentage-wise you end up losing a lot more on the SetRenderState calls. SlimDX incorporates a tuned math library that generally performs very well, although you have to be a bit careful with it. Profiling, even with a junker tool like NProf, highlights this stuff very quickly so it's not difficult to fix.

Overall, if we consider generic, completely optimal C++ and C# code doing rendering via D3D, the C# version is probably within 10-15% of the C++ version. That's hard to achieve though; consider how much time you're saving by working in C# which you can apply to higher level graphics optimizations that you probably simply wouldn't have time for if you had to build the entire thing in C++. And even if you managed to get that extra 10% in C++, it'd promptly shrink to 5% within a few months, when a new round of hardware tears through your application code faster than ever. I know what I'd pick -- which is why I wrote SlimDX to begin with.

OpenTK is subject to similar performance characteristics, with the caveat that their math library is rather slow in places. This is an implementation bug that I've discussed with them, and will hopefully be fixed before too long.