All in all, even this first pass of Mantle has delivered all that we’d hoped for:
Improved frame rate
Reduced CPU power consumption (important for laptops)
Less susceptible to frame rate spikes when other programs hit the CPU
Future scalability with higher numbers of cores
Scope for increasing scene and world complexity
Ability to increase the CPU budget for other systems like AI
The last two points are more relevant to our future games, and for now we need to see how this first pass of Mantle behaves in the wild and fix any issues that come up, before moving onto new features and improvements that would make sense to add to Sniper Elite 3. One big area that we haven't yet addressed which needs investigating is multiple GPU support - this can be a tricky area to get right.
The way DirectX11 handles multiple GPUs is “AFR” or Alternate Frame Rendering, which as the name suggests means if you have two comparably powered GPUs they simply take turns rendering frames. This is in many respects the easiest approach to take – and is a great way of making your game CPU bound! So possibly our Mantle version could show some big improvements when using this method.
However, with the independent control over the GPUs Mantle gives us, we could approach the problem very differently - for example one GPU could be rendering the basic geometry in the scene, while another handles lighting and shadows for the same frame, with the final image composited at the end. This may also provide a route for when GPUs aren't of a comparable power level – for example an integrated APU motherboard coupled with a desktop GPU. It’s the potential for completely new approaches like this which excites me the most about Mantle and the APIs which will follow it.
