Page 63 - Computer Power User - February 2017

Other signature DX12 capabilities
include volume tiled resources and
conservative rasterization, which are
both prerequisites for a realistic lighting
technique called Voxel Global Illumination.
This feature is also planned to be a part of
DX11.3, which seeks to backport some of
DX12’s features for Win7 and Win8/8.1
users. Conservative rasterization differs from
standard rasterization in that it is capable of
producing more accurate results with regard
to collision detection, occlusion culling,
and shadow acceleration. Other features
that require Win10 and DX12-compliant
hardware include Shader Model 5.1
support, shader-specified stencil reference
values, typed UAV load, standard swizzles,
default texture mapping, swap chains, The Xbox One even gets a taste of DirectX 12’s secret sauce.
swizzled resources, compressed resources,
and a series of new blend modes. In DX12,
raster ordered views enable real-time order- R.I.P. SLI & CrossFire respective CrossFire and SLI technologies,
independent transparency without crippling DX12’s new Explicit Multi-Adapter and the most common technique for
the rendering hardware. This feature could feature is another reason PC gamers can splitting game workloads between two or
be used to render more life-like blended get excited. It lets games detect scenarios more GPUs is AFR, or alternate frame
textures and complex transparent objects where more than one graphics adapter rendering. This essentially gives frame
such as smoke, fire, and water. New concise is present, from any vendor, and then No. 1 rendering duties to GPU A, and
pipeline state objects simplify how the enables the system to divvy up the frame No. 2 rendering duties to GPU B,
state-changing process occurs and unify workload in a variety of ways. Since and so on and so forth. DX9 through
the pipelines to slash overhead and let DirectX 9, successfully running multiple DX11’s APIs just saw two sequential
the graphics hardware perform more calls graphics adapters was heavily reliant on frames coming from a single chunk of
per frame. vendors AMD and NVIDIA and their graphics hardware.
AFR is essentially a
workaround for an API
that lacks specific support
for more than one graphics
adapter. It typically
wouldn’t work unless the
graphics adapters were
identical models or at least
very close to one another
in performance, and when
it worked, input lag was
a common side effect.
Furthermore, when you
run two graphics cards
with 4GB of GDDR5
each, for example, DX11
and prior APIs still only
recognize 4GB of total
memory, instead of the
combined 8GB. All frames
DirectX 12’s Explicit Multi-Adapter feature could render CrossFire and SLI unnecessary. rendered ultimately get
copied to both frame

CPU / February2017 63