Trilinear MIP against other approaches


  Approx. rendering time for a 256x256x100 data set and a 512x512 image
Result
Difference to ray casting MIP with trilinear interpolation
Raycasting MIP with trilinear interpolation
>10 sec.
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Ray casting with nearest-neighbor interpolation
>1 sec.
Shear warp projection with nearest neighbor interpolation during projection to the sheared image space and bilinear interpolation during the warp step (uses a sorted voxel array). 
~0.1 sec.
Sorted cell array MIP
~0.5 sec.