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</pre><pre class="rust ">
<span class="doccomment">//! A Dynamic Bounding Volume Tree.</span>

<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">cell</span>::<span class="ident">RefCell</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">rc</span>::<span class="ident">Rc</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">ptr</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>;
<span class="kw">use</span> <span class="ident">utils</span>::<span class="ident">data</span>::<span class="ident">owned_allocation_cache</span>::<span class="ident">OwnedAllocationCache</span>;
<span class="kw">use</span> <span class="ident">na</span>;
<span class="kw">use</span> <span class="ident">bounding_volume</span>::<span class="ident">BoundingVolume</span>;
<span class="kw">use</span> <span class="ident">partitioning</span>::<span class="ident">bvt_visitor</span>::<span class="ident">BVTVisitor</span>;
<span class="kw">use</span> <span class="ident">math</span>::<span class="ident">Point</span>;


<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">RustcEncodable</span>, <span class="ident">RustcDecodable</span>)]</span>
<span class="kw">enum</span> <span class="ident">UpdateState</span> {
    <span class="ident">NeedsShrink</span>,
    <span class="ident">UpToDate</span>
}

<span class="kw">type</span> <span class="ident">Cache</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">OwnedAllocationCache</span><span class="op">&lt;</span><span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span>;

<span class="doccomment">/// A Dynamic Bounding Volume Tree.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">DBVT</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="ident">cache</span>: <span class="ident">Cache</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
    <span class="ident">tree</span>:  <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span>,
    <span class="ident">len</span>:   <span class="ident">usize</span>
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="ident">DBVT</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="doccomment">/// Creates a new Dynamic Bounding Volume Tree.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-&gt;</span> <span class="ident">DBVT</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
        <span class="ident">DBVT</span> {
            <span class="ident">cache</span>: <span class="ident">OwnedAllocationCache</span>::<span class="ident">new</span>(),
            <span class="ident">tree</span>:  <span class="prelude-val">None</span>,
            <span class="ident">len</span>:   <span class="number">0</span>
        }
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="ident">DBVT</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>
    <span class="kw">where</span> <span class="ident">P</span>:  <span class="ident">Point</span>,
          <span class="ident">BV</span>: <span class="lifetime">&#39;static</span> <span class="op">+</span> <span class="ident">BoundingVolume</span><span class="op">&lt;</span><span class="ident">P</span><span class="op">&gt;</span> <span class="op">+</span> <span class="ident">Clone</span>,
          <span class="ident">B</span>:  <span class="lifetime">&#39;static</span> <span class="op">+</span> <span class="ident">Clone</span> {
    <span class="doccomment">/// Removes a leaf from the tree. Fails if the tree is empty.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">remove</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">leaf</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Rc</span><span class="op">&lt;</span><span class="ident">RefCell</span><span class="op">&lt;</span><span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span><span class="op">&gt;</span>) {
        <span class="kw">let</span> <span class="ident">self_tree</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">tree</span>.<span class="ident">take</span>().<span class="ident">expect</span>(<span class="string">&quot;This tree was empty.&quot;</span>);

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bleaf</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">leaf</span>).<span class="ident">borrow_mut</span>();
        <span class="self">self</span>.<span class="ident">tree</span> <span class="op">=</span> <span class="ident">bleaf</span>.<span class="ident">unlink</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">cache</span>, <span class="ident">self_tree</span>);
        <span class="self">self</span>.<span class="ident">len</span>  <span class="op">=</span> <span class="self">self</span>.<span class="ident">len</span> <span class="op">-</span> <span class="number">1</span>;
    }

    <span class="comment">// FIXME: it feels strange that this method takes (B, BV) in this order while the leaves</span>
    <span class="comment">// constructor takes (BV, B)…</span>
    <span class="doccomment">/// Creates, inserts, and returns a new leaf with the given content.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">insert_new</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">b</span>: <span class="ident">B</span>, <span class="ident">bv</span>: <span class="ident">BV</span>) <span class="op">-&gt;</span> <span class="ident">Rc</span><span class="op">&lt;</span><span class="ident">RefCell</span><span class="op">&lt;</span><span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="ident">leaf</span> <span class="op">=</span> <span class="ident">Rc</span>::<span class="ident">new</span>(<span class="ident">RefCell</span>::<span class="ident">new</span>(<span class="ident">DBVTLeaf</span>::<span class="ident">new</span>(<span class="ident">bv</span>, <span class="ident">b</span>)));

        <span class="self">self</span>.<span class="ident">insert</span>(<span class="ident">leaf</span>.<span class="ident">clone</span>());

        <span class="ident">leaf</span>
    }

    <span class="doccomment">/// Inserts a leaf to the tree.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">insert</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">leaf</span>: <span class="ident">Rc</span><span class="op">&lt;</span><span class="ident">RefCell</span><span class="op">&lt;</span><span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span><span class="op">&gt;</span>) {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">self_tree</span> <span class="op">=</span> <span class="prelude-val">None</span>;
        <span class="ident">mem</span>::<span class="ident">swap</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">self_tree</span>, <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">tree</span>);

        <span class="self">self</span>.<span class="ident">tree</span> <span class="op">=</span> <span class="kw">match</span> <span class="ident">self_tree</span> {
            <span class="prelude-val">None</span>    <span class="op">=&gt;</span> {
                <span class="ident">leaf</span>.<span class="ident">borrow_mut</span>().<span class="ident">parent</span> <span class="op">=</span> <span class="ident">DBVTLeafState</span>::<span class="ident">Root</span>;
                <span class="prelude-val">Some</span>(<span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="ident">leaf</span>))
            },
            <span class="prelude-val">Some</span>(<span class="ident">t</span>) <span class="op">=&gt;</span> <span class="prelude-val">Some</span>(<span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="ident">t</span>.<span class="ident">insert</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">cache</span>, <span class="ident">leaf</span>)))
        };

        <span class="self">self</span>.<span class="ident">len</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">len</span> <span class="op">+</span> <span class="number">1</span>;
    }

    <span class="doccomment">/// Traverses this tree using an object implementing the `BVTVisitor`trait.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// This will traverse the whole tree and call the visitor `.visit_internal(...)` (resp.</span>
    <span class="doccomment">/// `.visit_leaf(...)`) method on each internal (resp. leaf) node.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">visit</span><span class="op">&lt;</span><span class="ident">Vis</span>: <span class="ident">BVTVisitor</span><span class="op">&lt;</span><span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">visitor</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Vis</span>) {
        <span class="kw">match</span> <span class="self">self</span>.<span class="ident">tree</span> {
            <span class="prelude-val">Some</span>(<span class="kw-2">ref</span> <span class="ident">t</span>) <span class="op">=&gt;</span> <span class="ident">t</span>.<span class="ident">visit</span>(<span class="ident">visitor</span>),
            <span class="prelude-val">None</span>        <span class="op">=&gt;</span> { }
        }
    }
}

<span class="doccomment">/// Node of the Dynamic Bounding Volume Tree.</span>
<span class="kw">enum</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="ident">Internal</span>(<span class="ident">Box</span><span class="op">&lt;</span><span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span>),
    <span class="ident">Leaf</span>(<span class="ident">Rc</span><span class="op">&lt;</span><span class="ident">RefCell</span><span class="op">&lt;</span><span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span><span class="op">&gt;</span>),
    <span class="ident">Invalid</span>
}

<span class="doccomment">/// Internal node of a DBVT. An internal node always has two children.</span>
<span class="kw">struct</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="doccomment">/// The bounding volume of this node. It always encloses both its children bounding volumes.</span>
    <span class="ident">bounding_volume</span>: <span class="ident">BV</span>,
    <span class="doccomment">/// The center of this node bounding volume.</span>
    <span class="ident">center</span>:          <span class="ident">P</span>,
    <span class="doccomment">/// This node left child.</span>
    <span class="ident">left</span>:            <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
    <span class="doccomment">/// This node right child.</span>
    <span class="ident">right</span>:           <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
    <span class="doccomment">/// This node parent.</span>
    <span class="ident">parent</span>:          <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,

    <span class="ident">state</span>:           <span class="ident">UpdateState</span>
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>: <span class="ident">Point</span>, <span class="ident">BV</span>: <span class="ident">BoundingVolume</span><span class="op">&lt;</span><span class="ident">P</span><span class="op">&gt;</span>, <span class="ident">B</span><span class="op">&gt;</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="doccomment">/// Creates a new internal node.</span>
    <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">bounding_volume</span>: <span class="ident">BV</span>,
           <span class="ident">parent</span>:          <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
           <span class="ident">left</span>:            <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
           <span class="ident">right</span>:           <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>)
           <span class="op">-&gt;</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
        <span class="ident">DBVTInternal</span> {
            <span class="ident">center</span>:          <span class="ident">bounding_volume</span>.<span class="ident">center</span>(),
            <span class="ident">bounding_volume</span>: <span class="ident">bounding_volume</span>,
            <span class="ident">left</span>:            <span class="ident">left</span>,
            <span class="ident">right</span>:           <span class="ident">right</span>,
            <span class="ident">parent</span>:          <span class="ident">parent</span>,
            <span class="ident">state</span>:           <span class="ident">UpdateState</span>::<span class="ident">UpToDate</span>
        }
    }
}

<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>)]</span>
<span class="doccomment">/// State of a leaf.</span>
<span class="kw">enum</span> <span class="ident">DBVTLeafState</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="doccomment">/// This leaf is the root of a tree.</span>
    <span class="ident">Root</span>,
    <span class="doccomment">/// This leaf is the right child of another node.</span>
    <span class="ident">RightChildOf</span>(<span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>),
    <span class="doccomment">/// This leaf is the left child of another node.</span>
    <span class="ident">LeftChildOf</span>(<span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>),
    <span class="doccomment">/// This leaf is detached from any tree.</span>
    <span class="ident">Detached</span>
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="ident">DBVTLeafState</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="doccomment">/// Indicates whether this leaf is the root.</span>
    <span class="attribute">#[<span class="ident">inline</span>]</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_root</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
            <span class="ident">DBVTLeafState</span>::<span class="ident">Root</span> <span class="op">=&gt;</span> <span class="bool-val">true</span>,
            _ <span class="op">=&gt;</span> <span class="bool-val">false</span>
        }
    }

    <span class="doccomment">/// Indicates whether this leaf is detached.</span>
    <span class="attribute">#[<span class="ident">inline</span>]</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_detached</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
            <span class="ident">DBVTLeafState</span>::<span class="ident">Detached</span> <span class="op">=&gt;</span> <span class="bool-val">true</span>,
            _ <span class="op">=&gt;</span> <span class="bool-val">false</span>
        }
    }

    <span class="doccomment">/// Returns a pointer to this leaf parent and `true` if it is the left child.</span>
    <span class="attribute">#[<span class="ident">inline</span>]</span>
    <span class="kw">fn</span> <span class="ident">unwrap</span>(<span class="self">self</span>) <span class="op">-&gt;</span> (<span class="ident">bool</span>, <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>) {
        <span class="kw">match</span> <span class="self">self</span> {
            <span class="ident">DBVTLeafState</span>::<span class="ident">RightChildOf</span>(<span class="ident">p</span>) <span class="op">=&gt;</span> (<span class="bool-val">false</span>, <span class="ident">p</span>),
            <span class="ident">DBVTLeafState</span>::<span class="ident">LeftChildOf</span>(<span class="ident">p</span>)  <span class="op">=&gt;</span> (<span class="bool-val">true</span>, <span class="ident">p</span>),
            _ <span class="op">=&gt;</span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">&quot;Attempting to unwrap a root or detached node.&quot;</span>)
        }
    }
}

<span class="doccomment">/// Leaf of a Dynamic Bounding Volume Tree.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="doccomment">/// The bounding volume of this node.</span>
    <span class="kw">pub</span> <span class="ident">bounding_volume</span>: <span class="ident">BV</span>,
    <span class="doccomment">/// The center of this node bounding volume.</span>
    <span class="kw">pub</span> <span class="ident">center</span>:          <span class="ident">P</span>,
    <span class="doccomment">/// An user-defined object.</span>
    <span class="kw">pub</span> <span class="ident">object</span>:          <span class="ident">B</span>,
    <span class="doccomment">/// This node parent.</span>
    <span class="ident">parent</span>:              <span class="ident">DBVTLeafState</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="kw">fn</span> <span class="ident">take_internal</span>(<span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span> {
        <span class="kw">match</span> <span class="self">self</span> {
            <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="ident">i</span>) <span class="op">=&gt;</span> <span class="ident">i</span>,
            _ <span class="op">=&gt;</span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">&quot;DBVT internal error: this is not an internal node.&quot;</span>)
        }
    }

    <span class="kw">fn</span> <span class="ident">invalidate</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">res</span> <span class="op">=</span> <span class="ident">DBVTNode</span>::<span class="ident">Invalid</span>;

        <span class="ident">mem</span>::<span class="ident">swap</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">res</span>, <span class="self">self</span>);

        <span class="ident">res</span>
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="kw">fn</span> <span class="ident">is_right_internal_node</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">r</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>) <span class="op">-&gt;</span> <span class="ident">bool</span>
    {
        <span class="kw">match</span> <span class="self">self</span>.<span class="ident">right</span> {
            <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="kw-2">ref</span> <span class="ident">i</span>) <span class="op">=&gt;</span> <span class="kw-2">&amp;</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">i</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="op">==</span> <span class="kw-2">&amp;</span><span class="kw-2">*</span><span class="ident">r</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
            _ <span class="op">=&gt;</span> <span class="bool-val">false</span>
        }
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>: <span class="ident">Point</span>, <span class="ident">B</span>: <span class="lifetime">&#39;static</span>, <span class="ident">BV</span>: <span class="ident">BoundingVolume</span><span class="op">&lt;</span><span class="ident">P</span><span class="op">&gt;</span> <span class="op">+</span> <span class="lifetime">&#39;static</span><span class="op">&gt;</span> <span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
    <span class="doccomment">/// Creates a new leaf.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">bounding_volume</span>: <span class="ident">BV</span>, <span class="ident">object</span>: <span class="ident">B</span>) <span class="op">-&gt;</span> <span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> {
        <span class="ident">DBVTLeaf</span> {
            <span class="ident">center</span>:          <span class="ident">bounding_volume</span>.<span class="ident">center</span>(),
            <span class="ident">bounding_volume</span>: <span class="ident">bounding_volume</span>,
            <span class="ident">object</span>:          <span class="ident">object</span>,
            <span class="ident">parent</span>:          <span class="ident">DBVTLeafState</span>::<span class="ident">Detached</span>
        }
    }

    <span class="doccomment">/// Tests if this node is the root.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_root</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="self">self</span>.<span class="ident">parent</span>.<span class="ident">is_root</span>()
    }

    <span class="doccomment">/// Tests if this node has no parent.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_detached</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="self">self</span>.<span class="ident">parent</span>.<span class="ident">is_detached</span>()
    }

    <span class="doccomment">/// Removes this leaf from the tree.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// Returns the new root of the tree.</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// # Arguments:</span>
    <span class="doccomment">/// * `curr_root`: current root of the tree.</span>
    <span class="kw">fn</span> <span class="ident">unlink</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>,
              <span class="ident">cache</span>:     <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Cache</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
              <span class="ident">curr_root</span>: <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>) <span class="op">-&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span> {
        <span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">is_root</span>() {
            <span class="kw">let</span> (<span class="ident">is_left</span>, <span class="ident">p</span>) <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">replace</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">parent</span>, <span class="ident">DBVTLeafState</span>::<span class="ident">Detached</span>).<span class="ident">unwrap</span>();

            <span class="kw">let</span> <span class="ident">pp</span>           <span class="op">=</span> <span class="kw">unsafe</span> { (<span class="kw-2">*</span><span class="ident">p</span>).<span class="ident">parent</span> };
            <span class="kw">let</span> <span class="ident">parent_left</span>  <span class="op">=</span> <span class="kw">unsafe</span> { (<span class="kw-2">*</span><span class="ident">p</span>).<span class="ident">left</span>.<span class="ident">invalidate</span>() };
            <span class="kw">let</span> <span class="ident">parent_right</span> <span class="op">=</span> <span class="kw">unsafe</span> { (<span class="kw-2">*</span><span class="ident">p</span>).<span class="ident">right</span>.<span class="ident">invalidate</span>() };

            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">other</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">is_left</span> { <span class="ident">parent_right</span> } <span class="kw">else</span> { <span class="ident">parent_left</span> };

            <span class="kw">if</span> <span class="op">!</span><span class="ident">pp</span>.<span class="ident">is_null</span>() {
                <span class="kw">let</span> <span class="ident">is_p_right_to_pp</span> <span class="op">=</span> <span class="kw">unsafe</span> { (<span class="kw-2">*</span><span class="ident">pp</span>).<span class="ident">is_right_internal_node</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">p</span>) };
                <span class="comment">// we are far away from the root</span>
                <span class="kw">unsafe</span> {
                    <span class="kw">match</span> <span class="ident">other</span> {
                        <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">i</span>) <span class="op">=&gt;</span> <span class="ident">i</span>.<span class="ident">parent</span> <span class="op">=</span> <span class="ident">pp</span>,
                        <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">l</span>)     <span class="op">=&gt;</span> {
                            (<span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">l</span>).<span class="ident">borrow_mut</span>().<span class="ident">parent</span> <span class="op">=</span>
                                <span class="kw">if</span> <span class="ident">is_p_right_to_pp</span> { <span class="ident">DBVTLeafState</span>::<span class="ident">RightChildOf</span>(<span class="ident">pp</span>) }
                                <span class="kw">else</span> { <span class="ident">DBVTLeafState</span>::<span class="ident">LeftChildOf</span>(<span class="ident">pp</span>) }
                        },
                        <span class="ident">DBVTNode</span>::<span class="ident">Invalid</span> <span class="op">=&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>()
                    }

                    <span class="kw">if</span> <span class="ident">is_p_right_to_pp</span> {
                        <span class="ident">mem</span>::<span class="ident">swap</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">pp</span>).<span class="ident">right</span>, <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">other</span>);
                        <span class="comment">// NOTE: the children have already been invalidated before</span>
                        <span class="ident">cache</span>.<span class="ident">retain</span>(<span class="ident">other</span>.<span class="ident">take_internal</span>())
                    }
                    <span class="kw">else</span> {
                        <span class="ident">mem</span>::<span class="ident">swap</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">pp</span>).<span class="ident">left</span>, <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">other</span>);
                        <span class="comment">// NOTE: the children have already been invalidated before</span>
                        <span class="ident">cache</span>.<span class="ident">retain</span>(<span class="ident">other</span>.<span class="ident">take_internal</span>())
                    }

                    (<span class="kw-2">*</span><span class="ident">pp</span>).<span class="ident">state</span> <span class="op">=</span> <span class="ident">UpdateState</span>::<span class="ident">NeedsShrink</span>;
                }

                <span class="prelude-val">Some</span>(<span class="ident">curr_root</span>)
            }
            <span class="kw">else</span> {
                <span class="comment">// the root changes to the other child</span>
                <span class="kw">match</span> <span class="ident">other</span> {
                    <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">i</span>) <span class="op">=&gt;</span> <span class="ident">i</span>.<span class="ident">parent</span> <span class="op">=</span> <span class="ident">ptr</span>::<span class="ident">null_mut</span>(),
                    <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="kw-2">ref</span> <span class="ident">l</span>)         <span class="op">=&gt;</span> (<span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">l</span>).<span class="ident">borrow_mut</span>().<span class="ident">parent</span> <span class="op">=</span> <span class="ident">DBVTLeafState</span>::<span class="ident">Root</span>,
                    <span class="ident">DBVTNode</span>::<span class="ident">Invalid</span>             <span class="op">=&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>()
                }

                <span class="prelude-val">Some</span>(<span class="ident">other</span>)
            }
        }
        <span class="kw">else</span> {
            <span class="self">self</span>.<span class="ident">parent</span> <span class="op">=</span> <span class="ident">DBVTLeafState</span>::<span class="ident">Detached</span>;

            <span class="comment">// the tree becomes empty</span>
            <span class="prelude-val">None</span>
        }
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">BV</span>, <span class="ident">B</span><span class="op">&gt;</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>
    <span class="kw">where</span> <span class="ident">P</span>:  <span class="ident">Point</span>,
          <span class="ident">BV</span>: <span class="lifetime">&#39;static</span> <span class="op">+</span> <span class="ident">BoundingVolume</span><span class="op">&lt;</span><span class="ident">P</span><span class="op">&gt;</span>,
          <span class="ident">B</span>: <span class="lifetime">&#39;static</span> {
    <span class="kw">fn</span> <span class="ident">sqdist_to</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">to</span>: <span class="kw-2">&amp;</span><span class="ident">P</span>) <span class="op">-&gt;</span> <span class="ident">P</span>::<span class="ident">Real</span> {
        <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
            <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="kw-2">ref</span> <span class="ident">i</span>) <span class="op">=&gt;</span> <span class="ident">na</span>::<span class="ident">distance_squared</span>(<span class="kw-2">&amp;</span><span class="ident">i</span>.<span class="ident">center</span>, <span class="ident">to</span>),
            <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="kw-2">ref</span> <span class="ident">l</span>)     <span class="op">=&gt;</span> {
                <span class="kw">let</span> <span class="ident">bl</span> <span class="op">=</span> <span class="ident">l</span>.<span class="ident">borrow</span>();
                <span class="ident">na</span>::<span class="ident">distance_squared</span>(<span class="kw-2">&amp;</span><span class="ident">bl</span>.<span class="ident">center</span>, <span class="ident">to</span>)
            },
            <span class="ident">DBVTNode</span>::<span class="ident">Invalid</span> <span class="op">=&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>()
        }
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>
    <span class="kw">where</span> <span class="ident">P</span>:  <span class="ident">Point</span>,
          <span class="ident">BV</span>: <span class="lifetime">&#39;static</span> <span class="op">+</span> <span class="ident">BoundingVolume</span><span class="op">&lt;</span><span class="ident">P</span><span class="op">&gt;</span>,
          <span class="ident">B</span>:  <span class="lifetime">&#39;static</span> {
    <span class="kw">fn</span> <span class="ident">is_closest_to_left</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pt</span>: <span class="kw-2">&amp;</span><span class="ident">P</span>) <span class="op">-&gt;</span> <span class="ident">bool</span> {
        <span class="self">self</span>.<span class="ident">right</span>.<span class="ident">sqdist_to</span>(<span class="ident">pt</span>) <span class="op">&gt;</span> <span class="self">self</span>.<span class="ident">left</span>.<span class="ident">sqdist_to</span>(<span class="ident">pt</span>)
    }
}

<span class="kw">impl</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">BV</span>, <span class="ident">B</span><span class="op">&gt;</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>
    <span class="kw">where</span> <span class="ident">P</span>:  <span class="ident">Point</span>,
          <span class="ident">BV</span>: <span class="lifetime">&#39;static</span> <span class="op">+</span> <span class="ident">BoundingVolume</span><span class="op">&lt;</span><span class="ident">P</span><span class="op">&gt;</span>,
          <span class="ident">B</span>:  <span class="lifetime">&#39;static</span> {
    <span class="doccomment">/// Inserts a new leaf on this tree.</span>
    <span class="kw">fn</span> <span class="ident">insert</span>(<span class="self">self</span>,
              <span class="ident">cache</span>:     <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Cache</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>,
              <span class="ident">to_insert</span>: <span class="ident">Rc</span><span class="op">&lt;</span><span class="ident">RefCell</span><span class="op">&lt;</span><span class="ident">DBVTLeaf</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span><span class="op">&gt;</span>)
              <span class="op">-&gt;</span> <span class="ident">Box</span><span class="op">&lt;</span><span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span> {
        <span class="macro">assert</span><span class="macro">!</span>(<span class="ident">to_insert</span>.<span class="ident">borrow</span>().<span class="ident">is_detached</span>(), <span class="string">&quot;Cannot insert the same node twice.&quot;</span>);

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bto_insert</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">to_insert</span>).<span class="ident">borrow_mut</span>();
        <span class="kw">let</span> <span class="ident">pto_insert</span>     <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">bto_insert</span>;

        <span class="kw">match</span> <span class="self">self</span> {
            <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="ident">i</span>) <span class="op">=&gt;</span> {
                <span class="comment">/*
                 * NOTE: the insersion is done with unsafe pointers.
                 * This is so because using &amp;mut references dont seem to be possible since we have
                 * to take successive references to nodes contents.
                 */</span>

                <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">mut_internal</span> <span class="op">=</span> <span class="ident">i</span>;
                <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">parent</span>       <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">mut_internal</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>;

                <span class="kw">unsafe</span> {
                    (<span class="kw-2">*</span><span class="ident">parent</span>).<span class="ident">bounding_volume</span>.<span class="ident">merge</span>(<span class="kw-2">&amp;</span><span class="ident">pto_insert</span>.<span class="ident">bounding_volume</span>);

                    <span class="comment">// iteratively go to the leaves</span>
                    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">curr</span>;
                    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">left</span>;

                    <span class="kw">if</span> (<span class="kw-2">*</span><span class="ident">parent</span>).<span class="ident">is_closest_to_left</span>(<span class="kw-2">&amp;</span><span class="ident">pto_insert</span>.<span class="ident">center</span>) {
                        <span class="ident">curr</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">parent</span>).<span class="ident">left</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>;
                        <span class="ident">left</span> <span class="op">=</span> <span class="bool-val">true</span>;
                    }
                    <span class="kw">else</span> {
                        <span class="ident">curr</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> (<span class="kw-2">*</span><span class="ident">parent</span>).<span class="ident">right</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>;
                        <span class="ident">left</span> <span class="op">=</span> <span class="bool-val">false</span>;
                    }

                    <span class="kw">loop</span> {
                        <span class="kw">match</span> <span class="kw-2">*</span><span class="ident">curr</span> {
                            <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">ci</span>) <span class="op">=&gt;</span> {
                                <span class="comment">// FIXME: we could avoid the systematic merge</span>
                                <span class="ident">ci</span>.<span class="ident">bounding_volume</span>.<span class="ident">merge</span>(<span class="kw-2">&amp;</span><span class="ident">pto_insert</span>.<span class="ident">bounding_volume</span>);

                                <span class="kw">if</span> <span class="ident">ci</span>.<span class="ident">is_closest_to_left</span>(<span class="kw-2">&amp;</span><span class="ident">pto_insert</span>.<span class="ident">center</span>) { <span class="comment">// FIXME</span>
                                    <span class="ident">curr</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">ci</span>.<span class="ident">left</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>;
                                    <span class="ident">left</span> <span class="op">=</span> <span class="bool-val">true</span>;
                                }
                                <span class="kw">else</span> {
                                    <span class="ident">curr</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">ci</span>.<span class="ident">right</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTNode</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>;
                                    <span class="ident">left</span> <span class="op">=</span> <span class="bool-val">false</span>;
                                }

                                <span class="ident">parent</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">ci</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>;
                            },
                            <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="kw-2">ref</span> <span class="ident">l</span>) <span class="op">=&gt;</span> {
                                <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bl</span>       <span class="op">=</span> (<span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">l</span>).<span class="ident">borrow_mut</span>();
                                <span class="kw">let</span>     <span class="ident">pl</span>       <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">bl</span>;
                                <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">internal</span> <span class="op">=</span> <span class="ident">cache</span>.<span class="ident">alloc</span>(<span class="ident">DBVTInternal</span>::<span class="ident">new</span>(
                                    <span class="ident">pl</span>.<span class="ident">bounding_volume</span>.<span class="ident">merged</span>(<span class="kw-2">&amp;</span><span class="ident">pto_insert</span>.<span class="ident">bounding_volume</span>),
                                    <span class="ident">parent</span>,
                                    <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="ident">l</span>.<span class="ident">clone</span>()),
                                    <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="ident">to_insert</span>.<span class="ident">clone</span>())));

                                <span class="ident">pl</span>.<span class="ident">parent</span> <span class="op">=</span> <span class="ident">DBVTLeafState</span>::<span class="ident">LeftChildOf</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">internal</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>);
                                <span class="ident">pto_insert</span>.<span class="ident">parent</span> <span class="op">=</span>
                                    <span class="ident">DBVTLeafState</span>::<span class="ident">RightChildOf</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">internal</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>);

                                <span class="kw">if</span> <span class="ident">left</span> {
                                    (<span class="kw-2">*</span><span class="ident">parent</span>).<span class="ident">left</span> <span class="op">=</span> <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="ident">internal</span>)
                                }
                                <span class="kw">else</span> {
                                    (<span class="kw-2">*</span><span class="ident">parent</span>).<span class="ident">right</span> <span class="op">=</span> <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="ident">internal</span>)
                                }

                                <span class="kw">break</span>;
                            },
                            <span class="ident">DBVTNode</span>::<span class="ident">Invalid</span> <span class="op">=&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>()
                        }
                    }
                }

                <span class="ident">mut_internal</span>
            },
            <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="ident">l</span>) <span class="op">=&gt;</span> {
                <span class="kw">let</span>     <span class="ident">cl</span> <span class="op">=</span> <span class="ident">l</span>.<span class="ident">clone</span>();
                <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bl</span> <span class="op">=</span> (<span class="kw-2">*</span><span class="ident">cl</span>).<span class="ident">borrow_mut</span>();
                <span class="kw">let</span>     <span class="ident">pl</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">bl</span>;

                <span class="comment">// create the root</span>
                <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">root</span> <span class="op">=</span> <span class="ident">cache</span>.<span class="ident">alloc</span>(<span class="ident">DBVTInternal</span>::<span class="ident">new</span>(
                    <span class="ident">pl</span>.<span class="ident">bounding_volume</span>.<span class="ident">merged</span>(<span class="kw-2">&amp;</span><span class="ident">pto_insert</span>.<span class="ident">bounding_volume</span>),
                    <span class="ident">ptr</span>::<span class="ident">null_mut</span>(),
                    <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="ident">l</span>),
                    <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="ident">to_insert</span>.<span class="ident">clone</span>())));

                <span class="ident">pl</span>.<span class="ident">parent</span> <span class="op">=</span> <span class="ident">DBVTLeafState</span>::<span class="ident">LeftChildOf</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">root</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>);
                <span class="ident">pto_insert</span>.<span class="ident">parent</span> <span class="op">=</span> <span class="ident">DBVTLeafState</span>::<span class="ident">RightChildOf</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="ident">root</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">DBVTInternal</span><span class="op">&lt;</span><span class="ident">P</span>, <span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;</span>);

                <span class="ident">root</span>
            },
            <span class="ident">DBVTNode</span>::<span class="ident">Invalid</span> <span class="op">=&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>()
        }
    }

    <span class="kw">fn</span> <span class="ident">visit</span><span class="op">&lt;</span><span class="ident">Vis</span>: <span class="ident">BVTVisitor</span><span class="op">&lt;</span><span class="ident">B</span>, <span class="ident">BV</span><span class="op">&gt;&gt;</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">visitor</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Vis</span>) {
        <span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
            <span class="ident">DBVTNode</span>::<span class="ident">Internal</span>(<span class="kw-2">ref</span> <span class="ident">i</span>) <span class="op">=&gt;</span> {
                <span class="kw">if</span> <span class="ident">visitor</span>.<span class="ident">visit_internal</span>(<span class="kw-2">&amp;</span><span class="ident">i</span>.<span class="ident">bounding_volume</span>) {
                    <span class="ident">i</span>.<span class="ident">left</span>.<span class="ident">visit</span>(<span class="ident">visitor</span>);
                    <span class="ident">i</span>.<span class="ident">right</span>.<span class="ident">visit</span>(<span class="ident">visitor</span>);
                }
            },
            <span class="ident">DBVTNode</span>::<span class="ident">Leaf</span>(<span class="kw-2">ref</span> <span class="ident">l</span>) <span class="op">=&gt;</span> {
                <span class="kw">let</span> <span class="ident">bl</span> <span class="op">=</span> <span class="ident">l</span>.<span class="ident">borrow</span>();
                <span class="ident">visitor</span>.<span class="ident">visit_leaf</span>(<span class="kw-2">&amp;</span><span class="ident">bl</span>.<span class="ident">object</span>, <span class="kw-2">&amp;</span><span class="ident">bl</span>.<span class="ident">bounding_volume</span>)
            },
            <span class="ident">DBVTNode</span>::<span class="ident">Invalid</span> <span class="op">=&gt;</span> <span class="macro">unreachable</span><span class="macro">!</span>()
        }
    }
}

<span class="comment">// XXX: Drop should be implemented to invalidate the leaves parents when the tree is dropped.</span>
</pre>
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