| Q&A |
AMD DIRECTX 11,
Jon Story,
Dec - 2009
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“
DirectX 11 tessellation pipeline allows developers to
intuitively handle mesh density based upon factors such
as distance from camera – this is a very nice
way to handle LOD. We don’t think you will see
the disappearance of classic LOD overnight, but over
time we would expect more and more developers to choose
the tessellation route… ” |
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| Q1 |
ATI
is working for years in the field of mesh tesselation (N-Patch
technology). Are you satisfied with the way DX11 is handling
mesh tesselation? |
| A1 |
Yes,
DirectX 11 has defined a flexible tessellation pipeline that
allows for many different algorithms to be implemented. We
believe this will allow developers to be very creative in
their use of DirectX 11 hardware. We have already seen that
features such as characters, water and cloth benefit greatly
from tessellation in shipped games (see both DiRT2 & STALKER:
Call of Pripyat which are both already available in DirectX
11 form). As the original developers of hardware tessellation
on the GPU we’re naturally delighted to see it arrive
in this way as a key part of a true Open Standard. We have
worked very closely with Microsoft on DirectX 11 all the way
through the design and development of this powerful and flexible
new API, and this collaboration has allowed us to come to
market early and lead the way with DirectX 11 technology. |
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| Q2 |
With
dynamic tesselation : is it the end of LOD? |
| A2 |
Certainly
the DirectX 11 tessellation pipeline allows developers to
intuitively handle mesh density based upon factors such as
distance from camera – this is a very nice way to handle
LOD. We don’t think you will see the disappearance of
classic LOD overnight, but over time we would expect more
and more developers to choose the tessellation route…
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| Q3 |
With
dynamic tesselation : is it the end of bump mapping? |
| A3 |
We
would expect developers to start using displacement maps as
the high quality way to achieve micro detail. However it may
also be effective to tessellate objects to remove ugly silhouettes,
and still apply bump mapping. It is really down to the developer
to decide what works best for their particular application… |
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| Q4 |
How
can dynamic tesselation be faster than parallax occlusion mapping? |
| A4 |
Parallax
Occlusion Mapping (POM) was a great technique in its time,
however it was always an expensive cheat. The pixel shader
for POM was _very_ expensive indeed, and the effect suffered
from visual artifacts at certain viewing angles, and it
was not possible to achieve MSAA quality. Displacement mapping,
on the other hand, allows for a greatly simplified pixel
shader, and doesn’t suffer from the visual problems
that POM did. In short it’s the better way to solve
this problem, so we expect developers to adopt this readily…
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| Q5 |
For
games developpers : Is it easy too add mesh tesselation in their
3d engine? |
| A5 |
This
really depends on what flavor of tessellation they wish to add.
Some techniques like PN-Triangles (N-Patches), are very easy
to add, since the source art meshes may need no change –
this proved very effective in DiRT2. Obviously if displacement
mapping is desired then an artist needs to generate these texture
maps, and ensure that the models look correct with them applied.
A great example of how well this can be done is the Unigine
“Heaven” demo. This developer has integrated tessellation
with displacement maps into their tool chain, and is achieving
mind blowing results…
The adoption we’re seeing from developers is truly awesome,
see attached slide… |
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| Q6 |
For
3D artists : would they be able to take advantage of displacement
mapping? Is their a special 3d format that can control subdivision? |
| A6 |
Artists
would need a way to visualize their displacements on the final
model, that could be done via a plug-in to one of the 3D packages,
or via a custom build of their game engine that allows them
to view models in the final rendered state. This would be a
great question to ask to the Unigine developers since they have
clearly cracked this problem already… |
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| Q7 |
Would
it be possible for CAD or DCC softwares to take advantage of
this feature? |
| A7 |
There is nothing stopping these art tools from using the DirectX
11 tessellation pipeline, and I expect various plug-ins will
pop up as we go forward… |
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| Q8 |
Is
it possible to control tesselation with OpenGL API ? |
| A8 |
Yes,
it is possible to use our HW tessellator through OpenGL extensions… |
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