Use fixed size arrayvec in kdtree traversal

kdtree/Cargo.toml

@@ -4,8 +4,8 @@ version = "1.0.0"
 edition = "2021"
 
 [dependencies]
+arrayvec = "0.7.4"
 geometry = { version = "1.0.0", path = "../geometry" }
 glam = "0.28.0"
 rayon = { version = "1.10.0", default-features = false }
-smallvec = "1.13.2"
 textwrap = "0.16.1"

kdtree/src/build.rs

@@ -73,6 +73,13 @@ pub fn build_kdtree<B>(builder: B, max_depth: u32) -> KdTree
 where
     B: KdTreeBuilder,
 {
+    if max_depth as usize > super::MAX_DEPTH {
+        panic!(
+            "Max depth ({}) must be smaller than hard coded value ({}).",
+            max_depth,
+            super::MAX_DEPTH
+        );
+    }
     let root = build_helper(&builder, max_depth, 0, builder.starting_box());
     builder.make_tree(root)
 }

kdtree/src/lib.rs

@@ -1,13 +1,15 @@
 use std::{fmt::Display, ops::RangeInclusive};
 
+use arrayvec::ArrayVec;
 use geometry::{aap::Aap, geometric::Geometric, intersection::RayIntersection, ray::Ray, Geometry};
-use smallvec::SmallVec;
 
 pub mod build;
 pub mod build_sah;
 pub mod format;
 mod split;
 
+pub const MAX_DEPTH: usize = 20;
+
 fn intersect_closest(
     geometries: &[Geometric],
     indices: &[u32],
@@ -105,20 +107,19 @@ impl KdNode {
         let mut node = self;
         let mut t1 = *t_range.start();
         let mut t2 = *t_range.end();
-        let mut stack: SmallVec<[(&KdNode, f32, f32); 5]> = SmallVec::new();
+        let mut stack: ArrayVec<(&KdNode, f32, f32), MAX_DEPTH> = ArrayVec::new();
         loop {
             match node {
                 KdNode::Leaf(indices) => {
                     match intersect_closest(geometries, indices, ray, t1..=t2) {
                         Some(result) => return Some(result),
                         _ if t2 == *t_range.end() => return None,
-                        _ => {
-                            if let Some(s) = stack.pop() {
+                        _ => match stack.pop() {
+                            Some(s) => {
                                 (node, t1, t2) = s;
-                            } else {
-                                return None;
                             }
-                        }
+                            None => return None,
+                        },
                     }
                 }
                 KdNode::Node { plane, left, right } => {
@@ -134,7 +135,8 @@ impl KdNode {
                         } else if t < t1 {
                             node = far;
                         } else {
-                            stack.push((far, t, t2));
+                            let result = stack.try_push((far, t, t2));
+                            debug_assert!(result.is_ok());
                             node = near;
                             t2 = t;
                         }