Beginnings of BVH4 implementation.
- Created a traversal-order table. - Created a function to help index into that table.
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//! This BVH4 implementation pulls a lot of ideas from the paper
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//! "Efficient Ray Tracing Kernels for Modern CPU Architectures"
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//! by Fuetterling et al.
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//!
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//! Specifically, the table-based traversal order approach they
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//! propose is largely followed by this implementation.
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#![allow(dead_code)]
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use mem_arena::MemArena;
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use algorithm::partition;
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use bbox::BBox;
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use bbox4::BBox4;
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use boundable::Boundable;
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use lerp::lerp_slice;
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use ray::AccelRay;
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use super::bvh_base::{BVHBase, BVHBaseNode, BVH_MAX_DEPTH};
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// TRAVERSAL_TABLE
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include!("bvh4_table.inc");
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// Calculates the traversal code for a BVH4 node based on the splits and topology
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// of its children.
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//
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// split_1 is the top split.
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//
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// split_2 is either the left or right split depending on topology, and is only
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// relevant for topologies 0-2. For topology 3 it should be 0.
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//
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// split_3 is always the right split, and is only relevant for topology 0. For
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// topologies 1-3 it should be 0.
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//
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// topology can be 0-3:
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// 0: All three splits exist, representing 4 BVH4 children.
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// 1: Two splits exist: top split and left split, representing 3 BVH4 children.
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// 2: Two splits exist: top split and right split, representing 3 BVH4 children.
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// 3: Only the top split exists, representing 2 BVH4 children.
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fn calc_traversal_code(split_1: u8, split_2: u8, split_3: u8, topology: u8) -> u8 {
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debug_assert!(!(topology > 0 && split_3 > 0));
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debug_assert!(!(topology > 2 && split_2 > 0));
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static T_TABLE: [u8; 4] = [0, 27, 27 + 9, 27 + 9 + 9];
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split_1 + (split_2 * 3) + (split_3 * 9) + T_TABLE[topology as usize]
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}
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#[derive(Copy, Clone, Debug)]
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pub struct BVH4<'a> {
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@ -19,6 +53,12 @@ pub struct BVH4<'a> {
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#[derive(Copy, Clone, Debug)]
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enum BVH4Node<'a> {
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// Internal {
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// bounds: &'a [BBox4],
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// children: [&'a BVH4Node<'a>; 4],
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// children_count: u8,
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// traversal_code: u8,
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// },
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Internal {
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bounds: &'a [BBox],
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children: (&'a BVH4Node<'a>, &'a BVH4Node<'a>),
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35
src/accel/bvh4_table.inc
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35
src/accel/bvh4_table.inc
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static TRAVERSAL_TABLE: [[u8; 48]; 8] = [
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[228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228, 228,
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36, 36, 36, 36, 36, 36, 36, 36, 36,
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36, 36, 36, 36, 36, 36, 36, 36, 36,
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4, 4, 4],
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[27, 177, 177, 75, 180, 180, 75, 180, 180, 30, 225, 225, 78, 228, 228, 78, 228, 228, 30, 225, 225, 78, 228, 228, 78, 228, 228,
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6, 33, 33, 18, 36, 36, 18, 36, 36,
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6, 24, 24, 9, 36, 36, 9, 36, 36,
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1, 4, 4],
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[228, 78, 228, 225, 30, 225, 228, 78, 228, 180, 75, 180, 177, 27, 177, 180, 75, 180, 228, 78, 228, 225, 30, 225, 228, 78, 228,
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36, 18, 36, 33, 6, 33, 36, 18, 36,
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36, 9, 36, 24, 6, 24, 36, 9, 36,
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4, 1, 4],
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[27, 27, 177, 27, 27, 177, 75, 75, 180, 27, 27, 177, 27, 27, 177, 75, 75, 180, 30, 30, 225, 30, 30, 225, 78, 78, 228,
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6, 6, 33, 6, 6, 33, 18, 18, 36,
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6, 6, 24, 6, 6, 24, 9, 9, 36,
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1, 1, 4],
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[228, 228, 78, 228, 228, 78, 225, 225, 30, 228, 228, 78, 228, 228, 78, 225, 225, 30, 180, 180, 75, 180, 180, 75, 177, 177, 27,
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36, 36, 18, 36, 36, 18, 33, 33, 6,
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36, 36, 9, 36, 36, 9, 24, 24, 6,
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4, 4, 1],
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[27, 177, 27, 75, 180, 75, 27, 177, 27, 30, 225, 30, 78, 228, 78, 30, 225, 30, 27, 177, 27, 75, 180, 75, 27, 177, 27,
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6, 33, 6, 18, 36, 18, 6, 33, 6,
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6, 24, 6, 9, 36, 9, 6, 24, 6,
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1, 4, 1],
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[228, 78, 78, 225, 30, 30, 225, 30, 30, 180, 75, 75, 177, 27, 27, 177, 27, 27, 180, 75, 75, 177, 27, 27, 177, 27, 27,
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36, 18, 18, 33, 6, 6, 33, 6, 6,
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36, 9, 9, 24, 6, 6, 24, 6, 6,
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4, 1, 1],
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[27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
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6, 6, 6, 6, 6, 6, 6, 6, 6,
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6, 6, 6, 6, 6, 6, 6, 6, 6,
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1, 1, 1],
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];
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58
src/accel/create_bvh4_table.py
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58
src/accel/create_bvh4_table.py
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#!/usr/bin/env python
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if __name__ == "__main__":
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text = "static TRAVERSAL_TABLE: [[u8; 48]; 8] = [\n"
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for raydir in range(0, 8):
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ray = [raydir & 1, (raydir >> 1) & 1, (raydir >> 2) & 1]
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text += " ["
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for splits in [[s1, s2, s3] for s3 in range(0,3) for s2 in range(0,3) for s1 in range(0,3)]:
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perm = [0, 1, 2, 3]
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if ray[splits[1]] == 1:
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perm = [perm[1], perm[0]] + perm[2:4]
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if ray[splits[2]] == 1:
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perm = perm[0:2] + [perm[3], perm[2]]
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if ray[splits[0]] == 1:
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perm = perm[2:4] + perm[0:2]
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perm = perm[0] + (perm[1] << 2) + (perm[2] << 4) + (perm[3] << 6)
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text += "%d, " % perm
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text = text[:-1]
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text += "\n "
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for splits in [[s1, s2] for s2 in range(0,3) for s1 in range(0,3)]:
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perm = [0, 1, 2]
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if ray[splits[1]] == 1:
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perm = [perm[1], perm[0], perm[2]]
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if ray[splits[0]] == 1:
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perm = [perm[2], perm[0], perm[1]]
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perm = perm[0] + (perm[1] << 2) + (perm[2] << 4)
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text += "%d, " % perm
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text = text[:-1]
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text += "\n "
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for splits in [[s1, s2] for s2 in range(0,3) for s1 in range(0,3)]:
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perm = [0, 1, 2]
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if ray[splits[1]] == 1:
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perm = [perm[0], perm[2], perm[1]]
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if ray[splits[0]] == 1:
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perm = [perm[1], perm[2], perm[0]]
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perm = perm[0] + (perm[1] << 2) + (perm[2] << 4)
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text += "%d, " % perm
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text = text[:-1]
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text += "\n "
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for split in [s1 for s1 in range(0,3)]:
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perm = [0, 1]
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if ray[split] == 1:
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perm = [perm[1], perm[0]]
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perm = perm[0] + (perm[1] << 2)
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text += "%d, " % perm
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text = text[:-1]
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text = text[:-1] + "],\n"
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text += "];\n"
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print text
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