Game Development Reference

In-Depth Information

300

250

200

SLBVH

BVH

SKD-Tree

150

100

50

0

Conference Room

Standford Bunny

Welsh Dragon

Figure 1.6.

Memory footprint (MB) for different structures:

SLBVH with varying

depth, SAH-based BVH, and SKD-Tree.

1.5.3

Empty Nodes

Contrary to common structures, the SLBVH stores empty nodes in order to

satisfy the arithmetic operations (which allow us to traverse the heap without

a stack). The percentage of occupied nodes versus empty nodes is considerably

low, as shown in Figure 1.7. However, the geometry is not well partitioned given

that the middle-split scheme based on Morton codes is not optimal for balanced

distributions. On the other hand, using SAH for all levels (or perhaps just the

first few levels) of the structure might improve the tree quality. Yet, a tradeoff

between construction time and traversal performance must be accomplished. A

faster traversal does not mean a more e
cient structure on dynamic scenes.

9%

22%

31%

69%

78%

91%

(a)

(b)

(c)

Figure 1.7.
SLBVH nodes distribution. The red and blue colors represent empty nodes

and occupied nodes, respectively on the (a) Stanford Bunny (depth = 18), (b) Crytek

Sponza (depth = 21), and (c) Welsh Dragon (depth=23) models. The primitive-per-leaf

ratio is 1.72, 2.98, and 2.35, respectively.

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