Investigate 2-d textures performance

The use of 2-d textures should improve the percent of peak performance since it reduces the amount of indexing arithmetic required, but it seems to be decreasing it presently at more parameters.

This is a reminder to investigate why this is.

Is it an alignment requirement, e.g., the 2-d indexing should be consecutive in memory, perhaps the compiler is having to do an extra MOV to ensure this?
