Matt Pharr d7662b3eb9 Use reduce_equal() in volume rendering example to avoid some gathers. ...

Modified this example to use reduce_equal() to see if all of the program
instances want to load the 8 sample values around the same voxel.  When
this is the case, we can just do 8 scalar loads, rather than needing to
do a fully general gather.  Once this check fails, it isn't done again,
since it's not likely to start succeeding in the future.  This gives
a ~10% speedup with the low-res data set, and basically no performance
difference with the high-res one.  (It makes sense that the lower-resolution
the voxel sampling, the longer all of the rays will stay in the same set
of voxels.)

2011-08-17 12:37:07 +01:00

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