An empty tree node's bounds are inverted infinities, not the float limits

aephysics/dynamic_tree/module.ae

@@ -134,8 +134,14 @@ node_height(n: DynamicTreeNode) -> int {
     return n.height
 }
 
+// An empty node passes for a leaf, so only its bounds keep a traversal out:
+// inverted infinities, which no box overlaps, as the reference's are. The
+// float limits were not enough: a query box out to them overlapped, and the
+// empty node's proxy index read far past the proxies.
 make_empty_node() -> DynamicTreeNode {
-    return DynamicTreeNode { aabb: math.aabb_empty(), flag_index: EMPTY_NODE, height: 0 }
+    inf = math.infinity()
+    return DynamicTreeNode { aabb: AABB { lower: Vec3 { x: inf, y: inf, z: inf }, upper: Vec3 { x: 0.0 - inf, y: 0.0 - inf, z: 0.0 - inf } },
+                             flag_index: EMPTY_NODE, height: 0 }
 }
 
 // The pair below the root, or the root itself when it is a leaf.

aephysics/math/module.ae

@@ -37,7 +37,7 @@ exports (
     EPSILON, TINY, MAX_FLOAT, HUGE,
     vec2, vec3, quat, quat_vs, qv, transform, matrix3, aabb, plane,
     vec3_zero, vec3_one, vec3_axis_x, vec3_axis_y, vec3_axis_z,
-    quat_identity, transform_identity, mat3_zero, mat3_identity, aabb_empty,
+    quat_identity, transform_identity, mat3_zero, mat3_identity, aabb_empty, infinity,
     min_int, max_int, clamp_int, abs_float, min_float, max_float, clamp_float, lerp_float,
     sqrt_float, atan2_approx, compute_cos_sin, sin_approx, cos_approx, unwind_angle,
     add, sub, mul, neg, dot, length, length_squared, distance, distance_squared,
@@ -182,6 +182,13 @@ transform_identity() -> Transform { return Transform { p: vec3_zero(), q: quat_i
 mat3_zero() -> Matrix3 { return Matrix3 { cx: vec3_zero(), cy: vec3_zero(), cz: vec3_zero() } }
 mat3_identity() -> Matrix3 { return Matrix3 { cx: vec3_axis_x(), cy: vec3_axis_y(), cz: vec3_axis_z() } }
 // The box no point is in: a union with it is the other box.
+// IEEE positive infinity: past every finite double, as an empty tree node's
+// bounds must be so no finite query box overlaps them (b3MakeEmptyNode).
+infinity() -> float {
+    zero = 0.0
+    return 1.0 / zero
+}
+
 aabb_empty() -> AABB {
     return AABB { lower: Vec3 { x: MAX_FLOAT, y: MAX_FLOAT, z: MAX_FLOAT },
                   upper: Vec3 { x: 0.0 - MAX_FLOAT, y: 0.0 - MAX_FLOAT, z: 0.0 - MAX_FLOAT } }

tests/test_dynamic_tree.ae

@@ -160,6 +160,13 @@ test_leaf_root() {
     ensure("leaf root: the proxy", hit.proxy_id == proxy_id)
     ensure("leaf root: its user data", hit.user_data == (7 as long))
 
+    // A box out to the float limits: the empty node beside the leaf root is
+    // still skipped (its bounds are inverted infinities, not the limits).
+    hit.count = 0
+    everything = math.aabb(math.vec3(0.0 - math.MAX_FLOAT, 0.0 - math.MAX_FLOAT, 0.0 - math.MAX_FLOAT), math.vec3(math.MAX_FLOAT, math.MAX_FLOAT, math.MAX_FLOAT))
+    dynamic_tree.tree_query(&tree, everything, dynamic_tree.default_mask_bits(), false, leaf_root_visit, (&hit) as ptr)
+    ensure("leaf root: everything finds only the proxy (${hit.count})", hit.count == 1 && hit.proxy_id == proxy_id)
+
     hit.count = 0
     miss_box = math.aabb(math.vec3(4.0, 4.0, 4.0), math.vec3(5.0, 5.0, 5.0))
     dynamic_tree.tree_query(&tree, miss_box, dynamic_tree.default_mask_bits(), false, leaf_root_visit, (&hit) as ptr)