GeForce GTX 980 Whitepaper
MAXWELL: ENABLING THE NEXT
FRONTIER IN PC GRAPHICS
22
Figure 11: Illustration of conservative raster coverage rules
Hardware support for conservative raster is very helpful for the coverage phase of voxelization. In this
phase, fractional coverage of each voxel needs to be determined with high accuracy to ensure the
voxelized 3D grid represents the original 3D triangle data properly. Conservative raster helps the
hardware to perform this calculation efficiently; without conservative raster there are workarounds that
can be used to achieve the same result, but they are much more expensive.
The benefit of these features can be measured by running the voxelization stage of VXGI both ways (i.e.,
with the new features enabled vs. disabled). Figure 12 below compares the performance of voxelization
on “San Miguel,” a popular test scene for global illumination algorithms—GTX 980 achieves a 3x
speedup when these features are enabled.
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