Equidistant samples of a "left-eye" ray correspond to samples of equidistant
"right-eye" rays: The 
-value will increase at each sample by 
( 
), where denotes the distance of two samples
of the "left-eye" ray.
If the left-eye rays are processed sequenzially along scan-lines, the
-projection values from two consecutive left-eye rays with distance
will equally differ by the constant .
To accelerate the computation, left-eye samples are accumulated only until
full opacity is reached. To avoid that right-eye rays are terminated too
early, the accumulated opacities of the right-eye samples are re-examined. If
the accumulated opacity of a ray is not 1.0 and whose last projection is not
on the far side of the volume bounding box, sampling of this right-eye ray is
continued.
Problem of this Algorithm[]: The sampling points of this algorithm are not reprojected onto the integer grids of the right image. Round the re-projected samples to their nearest integer value. As a result errors are introduced.