Graphics Reference
In-Depth Information
Profile
SM Res
First
N
Slices
N
Samples
Time, Mem,
×N
Cscd
cascade
ms
MB
2048
2
×
6
Brute force
1
304
2048
2
×
6
High qual
1
2048
1024
9.14
160
1024
2
×
5
Balanced
1
1024
1024
3.45
56
1024
2
×
4
High perf
2
1024
512
2.73
28
Tab l e 2. 1.
Profile settings for NVidia GeForce GTX 680 (2560
×
1600 resolution).
3
2.5
2
1.5
1
0.5
0
Reconstruct
Camera Z
Render Coord
Texture
Render Coarse
Inscattering
Refine
Sampling
Build 1D
Min/max Trees
Ray March
Transform to
Rect Coords
High quality
Balanced
High performance
Figure 2.9.
Performance of different stages of the algorithm on NVidia GeForce GTX
680 (2560
×
1600 resolution).
shared between CPU and GPU). On each platform, we rendered the scattering
effects using brute force ray marching (which is run for every screen pixel and
does not exploit 1D min/max trees) and three different quality profiles: high qual-
ity, balanced, and high performance. Results for the first test platform (images
rendered at resolution of 2560
1600) can be found in Table 2.1 and Figure 2.9.
Table 2.2 and Figure 2.10 show results for the second platform (images rendered
at resolution of 1280
×
×
720). Initial epipolar line sampling step was set to 16 in
all the experiments.
On both platforms, the results in the high quality profile are visually identical
to the image generated by the brute force ray marching. At the same time,
the performance improvement over brute force algorithm is more than 33
×
and
8
.
8
on NVidia and Intel platforms correspondingly. The balanced quality profile
generates an image that is only slightly different from high quality and brute force
ray marching, but it gives an additional performance advantage of 2
.
6
×
×
on our test platforms. On NVidia GTX 680, less than 3.5 ms are required to
render the artifacts-free image at 2560
×
and 2
.
3
1600 resolution. The high performance
profile reduces the computation times further, but image quality suffers. It must
be noted that even in high performance profile, the rendered image still looks very
convincing, as Figure 2.11 shows. The image does not exhibit aliasing artifacts,
like stair-step patterns. Some temporal artifacts could be visible, but these are
caused by low shadow map resolution, which generally affects shadow quality.
×
