1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
use crate::partitioning::{
    BVTNodeId, BestFirstVisitStatus, BestFirstVisitor, DBVTNodeId, SimultaneousVisitor,
    VisitStatus, Visitor, BVT, DBVT,
};
use na::RealField;
use std::cmp::Ordering;
use std::collections::BinaryHeap;

/// Trait implemented by Bounding Volume Hierarchy.
pub trait BVH<T, BV> {
    /// Type of a node identifiers on this BVH.
    type Node: Copy;

    /// The root of the BVH.
    fn root(&self) -> Option<Self::Node>;
    /// The number of children of the given node.
    fn num_children(&self, node: Self::Node) -> usize;
    /// The i-th child of the given node.
    fn child(&self, i: usize, node: Self::Node) -> Self::Node;
    /// The bounding volume and data contained by the given node.
    fn content(&self, node: Self::Node) -> (&BV, Option<&T>);

    /// Traverses this BVH using a visitor.
    fn visit(&self, visitor: &mut impl Visitor<T, BV>) {
        // FIXME: find a way to avoid the allocation.
        let mut stack = Vec::new();

        if let Some(root) = self.root() {
            stack.push(root);

            while let Some(node) = stack.pop() {
                let content = self.content(node);

                match visitor.visit(content.0, content.1) {
                    VisitStatus::Continue => {
                        for i in 0..self.num_children(node) {
                            stack.push(self.child(i, node))
                        }
                    }
                    VisitStatus::ExitEarly => return,
                    VisitStatus::Stop => {}
                }
            }
        }
    }

    /// Visits the bounding volume test tree implicitly formed with `other`.
    fn visit_bvtt(&self, other: &impl BVH<T, BV>, visitor: &mut impl SimultaneousVisitor<T, BV>) {
        // FIXME: find a way to avoid the allocation.
        let mut stack = Vec::new();

        if let (Some(root1), Some(root2)) = (self.root(), other.root()) {
            stack.push((root1, root2));

            while let Some((node1, node2)) = stack.pop() {
                let content1 = self.content(node1);
                let content2 = other.content(node2);

                match visitor.visit(content1.0, content1.1, content2.0, content2.1) {
                    VisitStatus::Continue => {
                        let nchild1 = self.num_children(node1);
                        let nchild2 = other.num_children(node2);

                        match (nchild1, nchild2) {
                            (0, 0) => {}
                            (0, _) => {
                                for j in 0..nchild2 {
                                    let n2 = other.child(j, node2);
                                    stack.push((node1, n2))
                                }
                            }
                            (_, 0) => {
                                for i in 0..nchild1 {
                                    let n1 = self.child(i, node1);
                                    stack.push((n1, node2))
                                }
                            }
                            (_, _) => {
                                for i in 0..nchild1 {
                                    let n1 = self.child(i, node1);

                                    for j in 0..nchild2 {
                                        let n2 = other.child(j, node2);
                                        stack.push((n1, n2))
                                    }
                                }
                            }
                        }
                    }
                    VisitStatus::ExitEarly => return,
                    VisitStatus::Stop => {}
                }
            }
        }
    }

    /// Performs a best-first-search on the BVH.
    ///
    /// Returns the content of the leaf with the smallest associated cost, and a result of
    /// user-defined type.
    fn best_first_search<N, BFS>(&self, visitor: &mut BFS) -> Option<(Self::Node, BFS::Result)>
    where
        N: RealField,
        BFS: BestFirstVisitor<N, T, BV>,
    {
        let mut queue: BinaryHeap<WeightedValue<N, Self::Node>> = BinaryHeap::new();
        let mut best_cost = N::max_value();
        let mut best_result = None;

        if let Some(root) = self.root() {
            let (root_bv, root_data) = self.content(root);

            match visitor.visit(best_cost, root_bv, root_data) {
                BestFirstVisitStatus::Continue { cost, result } => {
                    if let Some(res) = result {
                        best_cost = cost;
                        best_result = Some((root, res));
                    }

                    queue.push(WeightedValue::new(root, -cost))
                }
                BestFirstVisitStatus::Stop => return None,
                BestFirstVisitStatus::ExitEarly(result) => return result.map(|res| (root, res)),
            }

            while let Some(entry) = queue.pop() {
                if -entry.cost >= best_cost {
                    break; // Solution found.
                }

                for i in 0..self.num_children(entry.value) {
                    let child = self.child(i, entry.value);
                    let (child_bv, child_data) = self.content(child);

                    match visitor.visit(best_cost, child_bv, child_data) {
                        BestFirstVisitStatus::Continue { cost, result } => {
                            if cost < best_cost {
                                if result.is_some() {
                                    best_cost = cost;
                                    best_result = result.map(|res| (child, res));
                                }

                                queue.push(WeightedValue::new(child, -cost))
                            }
                        }
                        BestFirstVisitStatus::ExitEarly(result) => {
                            return result.map(|res| (child, res)).or(best_result)
                        }
                        BestFirstVisitStatus::Stop => {}
                    }
                }
            }
        }

        best_result
    }
}

/// An enum grouping references to all the BVH implementations on ncollide.
#[derive(Copy, Clone)]
pub enum BVHImpl<'a, N: 'a + RealField, T: 'a, BV: 'a> {
    /// A static binary bounding volume tree.
    BVT(&'a BVT<T, BV>),
    /// A dynamic binary bounding volume tree.
    DBVT(&'a DBVT<N, T, BV>),
}

/// The Id of a node of a BVH.
pub enum BVHNodeId {
    // The Id of a BVT.
    BVTNodeId(BVTNodeId),
    // The Id of a DBVT.
    DBVTNodeId(DBVTNodeId),
}

impl<'a, N: RealField, T, BV> BVHImpl<'a, N, T, BV> {
    /// Gets the underlying reference to a BVT, or panics if this is not a `BVTImpl::BVT`.
    #[inline]
    pub fn unwrap_bvt(self) -> &'a BVT<T, BV> {
        match self {
            BVHImpl::BVT(bvt) => bvt,
            _ => panic!("This BVTImpl is not a BVT."),
        }
    }

    /// Gets the underlying reference to a DBVT, or panics if this is not a `BVTImpl::DBVT`.
    #[inline]
    pub fn unwrap_dbvt(self) -> &'a DBVT<N, T, BV> {
        match self {
            BVHImpl::DBVT(dbvt) => dbvt,
            _ => panic!("This BVTImpl is not a DBVT."),
        }
    }

    /// Traverses this tree using a visitor.
    pub fn visit(self, visitor: &mut impl Visitor<T, BV>) {
        match self {
            BVHImpl::BVT(bvt) => bvt.visit(visitor),
            BVHImpl::DBVT(dbvt) => dbvt.visit(visitor),
        }
    }

    /// Visits the bounding volume traversal tree implicitly formed with `other`.
    pub fn visit_bvtt(
        self,
        other: BVHImpl<N, T, BV>,
        visitor: &mut impl SimultaneousVisitor<T, BV>,
    ) {
        // Note: the dispatch on each pair is split into two method to avoid
        // having to write a manually a match over each possible pair.
        match other {
            BVHImpl::BVT(bvh2) => self.visit_bvtt_dispatch(bvh2, visitor),
            BVHImpl::DBVT(bvh2) => self.visit_bvtt_dispatch(bvh2, visitor),
        }
    }

    fn visit_bvtt_dispatch(
        self,
        bvh2: &impl BVH<T, BV>,
        visitor: &mut impl SimultaneousVisitor<T, BV>,
    ) {
        match self {
            BVHImpl::BVT(bvh1) => bvh1.visit_bvtt(bvh2, visitor),
            BVHImpl::DBVT(bvh1) => bvh1.visit_bvtt(bvh2, visitor),
        }
    }

    /// Performs a best-fist-search on the tree.
    ///
    /// Returns the content of the leaf with the smallest associated cost, and a result of
    /// user-defined type.
    pub fn best_first_search<BFS>(self, visitor: &mut BFS) -> Option<(BVHNodeId, BFS::Result)>
    where
        BFS: BestFirstVisitor<N, T, BV>,
    {
        match self {
            BVHImpl::BVT(bvt) => bvt
                .best_first_search(visitor)
                .map(|res| (BVHNodeId::BVTNodeId(res.0), res.1)),
            BVHImpl::DBVT(dbvt) => dbvt
                .best_first_search(visitor)
                .map(|res| (BVHNodeId::DBVTNodeId(res.0), res.1)),
        }
    }
}

struct WeightedValue<N, T> {
    pub value: T,
    pub cost: N,
}

impl<N, T> WeightedValue<N, T> {
    /// Creates a new reference packed with a cost value.
    #[inline]
    pub fn new(value: T, cost: N) -> WeightedValue<N, T> {
        WeightedValue {
            value: value,
            cost: cost,
        }
    }
}

impl<N: PartialEq, T> PartialEq for WeightedValue<N, T> {
    #[inline]
    fn eq(&self, other: &WeightedValue<N, T>) -> bool {
        self.cost.eq(&other.cost)
    }
}

impl<N: PartialEq, T> Eq for WeightedValue<N, T> {}

impl<N: PartialOrd, T> PartialOrd for WeightedValue<N, T> {
    #[inline]
    fn partial_cmp(&self, other: &WeightedValue<N, T>) -> Option<Ordering> {
        self.cost.partial_cmp(&other.cost)
    }
}

impl<N: PartialOrd, T> Ord for WeightedValue<N, T> {
    #[inline]
    fn cmp(&self, other: &WeightedValue<N, T>) -> Ordering {
        if self.cost < other.cost {
            Ordering::Less
        } else if self.cost > other.cost {
            Ordering::Greater
        } else {
            Ordering::Equal
        }
    }
}