Graphics Reference
In-Depth Information
Frame Voxelize Ray March Ray Sort Test ing
Sponza
92.6 ms
2.0 ms
9.9 ms
12.7 ms
54.2 ms
Sibenik
65.9 ms
0.6 ms
12.7 ms
15.4 ms
24.5 ms
Simple
31.3 ms
0.1 ms
9.2 ms
7.7 ms
5.4 ms
Tab l e 2. 1.
Time spent in each of the stages per frame. Total frame time includes
G-buffer generation, rendering of shadow maps, and deferred shading.
VS
GS
PS
Total
Pass 1 (trafo + cell-tri pairs)
0.9 ms
2.3 ms
7.8 ms
11.0 ms
Pass 2 (ray-tri intersections)
1.3 ms
3.0 ms
38.2 ms
42.4 ms
Tab l e 2. 2.
Time spent in each of the shaders in the two-pass load-balancing scheme
illustrated in Figure 2.9 (measured in the Sponza scene and summed for all batches of
triangles).
expected. Both geometry and rays are processed linearly and are therefore always
accessed in a perfectly coherent fashion.
Table 2.3 shows some additional figures for the number of ray links and inter-
section tests. As can be seen, storage requirements for the ray grid typically stay
below four links per ray. Across all passes, rays are enqueued to four to eight
occupied cells on average, depending on the scene complexity. As expected, the
number of hit tests per ray greatly depends on the number of triangles in the
scene.
Table 2.4 shows how rays and triangles are distributed across all ray grid cells
that are occupied by geometry and traversed by at least one ray. These numbers
vary greatly for different scenes. They depend on the way the geometry is laid
out, what parts are occluded, and how evenly the scene is tessellated.
Tests Hits Hit Ratio Max Links Total Links
Sponza
121.1
1.5
1.72%
3.8
7.5
Sibenik
27.9
1.1
4.1%
3.7
6.4
Simple
8.0
0.4
4.65%
2.5
3.9
Tab l e 2. 3.
Per ray, the hit tests, hits, maximum number of ray links per pass, and total
number of ray links (not stored) across all passes.
#rays/cell
# cells
μ
σ
>
10
μ
max
#tris/cell
Sponza
150K
32.9
261.6
1.66%
11670
15.4
Sibenik
138K
45.5
282.1
1.37%
9180
4.4
Simple
43K
58.8
461.3
1.95%
4131
2.1
Tab l e 2. 4.
Number of ray grid cells active during intersection testing, with distribution
of rays and triangles per cell;
μ
is the expected value and
σ
the standard deviation.
