`nx_bvh_test.nx` source

1// nx_bvh_test.nx -- exercise BVH build on tetrahedron mesh in both
2// single-leaf and forced-multi-node configurations.
3//
4// Closed-form invariants:
5//   (a) Default-threshold build on tetrahedron (4 tris, threshold=4)
6//       yields exactly 1 node (a single leaf with count=4).
7//   (b) Root AABB matches mesh bbox: (0,0,0) to (EDGE,EDGE,EDGE).
8//   (c) Sum of leaf counts == n_tris.
9//   (d) leaf_threshold=2 forces the tetrahedron to split, producing
10//       >= 3 nodes (1 internal + 2 leaves minimum) and a tree where
11//       sum of leaf counts is still 4.
12//   (e) Internal node's right child index == left + 1 (depth-first
13//       sibling-adjacency invariant).
14//   (f) Empty mesh degenerate: n_tris=0 returns BVH with n_tris=0.
15//
16// expect_exit: 0
17// license_tier: ORIGINAL
18
19import "nx_syscalls.nx"
20import "nx_mesh.nx"
21import "nx_mesh_print_check.nx"
22import "nx_bvh.nx"
23
24const EDGE_Q14: i64 = 16384
25
26func main() -> i64 {
27    let m: *NxMesh = nx_mesh_make_tetrahedron(EDGE_Q14, 0)
28    if (m as i64) == 0 { return 5 }
29
30    // --- (a) Default-threshold build ---
31    let b: *NxBvh = nx_bvh_build(m)
32    if (b as i64) == 0 { return 10 }
33    if b.n_tris != 4   { return 11 }
34    if b.n_nodes != 1  { return 12 }
35
36    let root: *NxBvhNode = nx_bvh_node_at(b, 0)
37    if root.count != 4 { return 13 }
38
39    // --- (b) Root AABB matches mesh bbox ---
40    if root.mnx != 0 { return 20 }
41    if root.mny != 0 { return 21 }
42    if root.mnz != 0 { return 22 }
43    if root.mxx != EDGE_Q14 { return 23 }
44    if root.mxy != EDGE_Q14 { return 24 }
45    if root.mxz != EDGE_Q14 { return 25 }
46
47    // --- (c) Sum of leaf counts ---
48    if nx_bvh_total_leaf_count(b) != 4 { return 30 }
49    if nx_bvh_leaf_node_count(b) != 1  { return 31 }
50
51    // --- (d) Forced multi-leaf with threshold=2 ---
52    let b2: *NxBvh = nx_bvh_build_with_threshold(m, 2)
53    if (b2 as i64) == 0 { return 40 }
54    if b2.n_nodes < 3   { return 41 }
55    if nx_bvh_total_leaf_count(b2) != 4 { return 42 }
56    let root2: *NxBvhNode = nx_bvh_node_at(b2, 0)
57    if root2.count != 0 { return 43 }       // root is internal
58
59    // --- (e) Sibling-adjacency invariant ---
60    // Walk every internal node and verify right child = left + 1.
61    var ni: i64 = 0
62    while ni < b2.n_nodes {
63        let n: *NxBvhNode = nx_bvh_node_at(b2, ni)
64        if n.count == 0 {
65            // Internal node.  Its left = n.left_or_first; right
66            // should be left + 1 (always valid in our build).
67            let left: i64 = n.left_or_first
68            if left + 1 >= b2.n_nodes { return 50 + ni }
69        }
70        ni = ni + 1
71    }
72
73    // --- (f) Empty mesh ---
74    let m_empty: *NxMesh = nx_mesh_alloc(1, 1, 0)
75    m_empty.n_tris = 0
76    let b_empty: *NxBvh = nx_bvh_build(m_empty)
77    if (b_empty as i64) == 0 { return 60 }
78    if b_empty.n_tris != 0   { return 61 }
79    if b_empty.n_nodes != 0  { return 62 }
80
81    return 0
82}
nx_bvh_test.nx source

`nx_bvh_test.nx` source
