APPARATUS AND METHOD FOR INTRA-BVH LEVEL-OF-DETAIL SELECTION

1 . A graphics processor comprising:

a ray generator to generate a ray to be traversed through a bounding volume hierarchy (BVH) including at least one multi-level-of-detail (multi LoD) node comprising a first child node associated with a first LoD and a second child node associated with a second LoD, wherein the first LoD comprises a relatively coarser LoD than the second LoD;

traversal hardware logic to traverse the ray through the BVH, wherein upon reaching the multi-LoD node, the traversal hardware logic is to determine whether to continue traversal with the first child node or the second child node based on a comparison between an LoD node bitmask associated with the multi-LoD node and a per-ray bitmask associated with the ray;

the traversal hardware logic to continue traversing the ray through either the first child node or the second child node based on a result of the comparison.

2 . The graphics processor of claim 1 further comprising:

comparison logic to perform the comparison between the LoD node bitmask and the per-ray bitmask, wherein the comparison comprises at least one of: a greater than or equal to comparison, a less than or equal to comparison, a greater than comparison, a less than comparison, and an equal to comparison.

3 . The graphics processor of claim 2 further comprising:

a BVH builder to construct the BVH in accordance with primitives of a graphics scene, the BVH builder to construct the at least one multi-LoD node based on a parent micropolygon cluster comprising a plurality of child micropolygon clusters.

4 . The graphics processor of claim 3 wherein the BVH builder is to construct the first child associated with a relatively coarser LoD over the parent micropolygon cluster and is to construct the second child with a relatively finer LoD over at least one of the child micropolygon clusters.

5 . The graphics processor of claim 3 wherein the BVH builder, upon determining that a new LoD is required which is different from the first LoD and the second LoD, is to rebuild the BVH, or portion thereof, to include a new multi-LoD node with at least one child node associated with the new LoD.

6 . The graphics processor of claim 3 further comprising:

intersection logic to determine whether the ray intersects at least one of the primitives and to responsively generate a result indicating a hit or a miss.

7 . The graphics processor of claim 1 wherein the LoD node bitmask and the per-ray bitmask comprise values having a size of 8-bits, 16-bits, or 32-bits.

8 . The graphics processor of claim 7 wherein the size is selected to have a sufficient number of bits to reduce artifacts associated with stochastic LoD transitioning.

9 . A method comprising:

generating a ray to be traversed through a bounding volume hierarchy (BVH) including at least one multi-level-of-detail (multi LoD) node comprising a first child node associated with a first LoD and a second child node associated with a second LoD, wherein the first LoD comprises a relatively coarser LoD than the second LoD;

traversing the ray through the BVH, wherein upon reaching the multi-LoD node, determining whether to continue traversal with the first child node or the second child node based on a comparison between an LoD node bitmask associated with the multi-LoD node and a per-ray bitmask associated with the ray;

continue traversing of the ray through either the first child node or the second child node based on a result of the comparison.

10 . The method of claim 9 wherein the comparison comprises at least one of: a greater than or equal to comparison, a less than or equal to comparison, a greater than comparison, a less than comparison, and an equal to comparison.

11 . The method of claim 10 further comprising:

constructing the BVH in accordance with primitives of a graphics scene, including constructing the at least one multi-LoD node based on a parent micropolygon cluster comprising a plurality of child micropolygon clusters.

12 . The method of claim 11 the first child associated with a relatively coarser LoD is to be constructed over the parent micropolygon cluster and the second child with a relatively finer LoD is to be constructed over at least one of the child micropolygon clusters.

13 . The method of claim 11 wherein, upon determining that a new LoD is required which is different from the first LoD and the second LoD, rebuilding the BVH, or portion thereof, to include a new multi-LoD node with at least one child node associated with the new LoD.

14 . The method of claim 11 further comprising:

determining whether the ray intersects at least one of the primitives and responsively generating a result indicating a hit or a miss.

15 . The method of claim 9 wherein the LoD node bitmask and the per-ray bitmask comprise values having a size of 8-bits, 16-bits, or 32-bits.

16 . The method of claim 15 wherein the size is selected to have a sufficient number of bits to reduce artifacts associated with stochastic LoD transitioning.

17 . A machine-readable medium having program code stored thereon which, when executed by a machine, cause the machine to perform the operations of:

generating a ray to be traversed through a bounding volume hierarchy (BVH) including at least one multi-level-of-detail (multi LoD) node comprising a first child node associated with a first LoD and a second child node associated with a second LoD, wherein the first LoD comprises a relatively coarser LoD than the second LoD;

traversing the ray through the BVH, wherein upon reaching the multi-LoD node, determining whether to continue traversal with the first child node or the second child node based on a comparison between an LoD node bitmask associated with the multi-LoD node and a per-ray bitmask associated with the ray;

continue traversing of the ray through either the first child node or the second child node based on a result of the comparison.

18 . The machine-readable medium of claim 17 wherein the comparison comprises at least one of: a greater than or equal to comparison, a less than or equal to comparison, a greater than comparison, a less than comparison, and an equal to comparison.

19 . The machine-readable medium of claim 18 further comprising program code to cause the machine to perform the operation of:

constructing the BVH in accordance with primitives of a graphics scene, including constructing the at least one multi-LoD node based on a parent micropolygon cluster comprising a plurality of child micropolygon clusters.

20 . The machine-readable medium of claim 19 the first child associated with a relatively coarser LoD is to be constructed over the parent micropolygon cluster and the second child with a relatively finer LoD is to be constructed over at least one of the child micropolygon clusters.

21 . The machine-readable medium of claim 19 wherein, upon determining that a new LoD is required which is different from the first LoD and the second LoD, rebuilding the BVH, or portion thereof, to include a new multi-LoD node with at least one child node associated with the new LoD.

22 . The machine-readable medium of claim 19 further comprising program code to cause the machine to perform the operation of:

determining whether the ray intersects at least one of the primitives and responsively generating a result indicating a hit or a miss.

23 . The machine-readable medium of claim 18 wherein the LoD node bitmask and the per-ray bitmask comprise values having a size of 8-bits, 16-bits, or 32-bits.

24 . The machine-readable medium of claim 23 wherein the size is selected to have a sufficient number of bits to reduce artifacts associated with stochastic LoD transitioning.