  Ray tracing is an essential operation for realistic image synthesis. The
acceleration of ray tracing has been studied for a long period of time because
algorithms such as light transport simulations require a large amount of ray
tracing. One of the major approaches to accelerate the intersections is to use
bounding volumes for early pruning for primitives in the volume. The
axis-aligned bounding box is a popular bounding volume for ray tracing because
of its simplicity and efficiency. However, the conservative bounding volume may
produce extra empty space in addition to its content. Especially, primitives
that are thin and diagonal to the axis give false-positive hits on the box
volume due to the extra space. Although more complex bounding volumes such as
oriented bounding boxes may reduce more false-positive hits, they are
computationally expensive. In this paper, we propose a novel culling approach
to reduce false-positive hits for the bounding box by embedding a binary voxel
data structure to the volume. As a ray is represented as a conservative voxel
volume as well in our approach, the ray--voxel intersection is cheaply done by
bitwise AND operations. Our method is applicable to hierarchical data
structures such as bounding volume hierarchy (BVH). It reduces false-positive
hits due to the ray--box test and reduces the number of intersections during
the traversal of BVH in ray tracing. We evaluate the reduction of intersections
with several scenes and show the possibility of performance improvement despite
the culling overhead. We also introduce a compression approach with a lookup
table for our voxel data. We show that our compressed voxel data achieves
significant false-positive reductions with a small amount of memory.
