Add collision groups to filter collision pairs.

src/geometry/collider.rs

@@ -1,7 +1,7 @@
 use crate::dynamics::{MassProperties, RigidBodyHandle, RigidBodySet};
 use crate::geometry::{
-    Ball, Capsule, ColliderGraphIndex, Contact, Cuboid, HeightField, InteractionGraph, Proximity,
+    Ball, Capsule, ColliderGraphIndex, Contact, Cuboid, HeightField, InteractionGraph,
-    Segment, Shape, ShapeType, Triangle, Trimesh,
+    InteractionGroups, Proximity, Segment, Shape, ShapeType, Triangle, Trimesh,
 };
 #[cfg(feature = "dim3")]
 use crate::geometry::{Cone, Cylinder, RoundCylinder};
@@ -203,6 +203,7 @@ pub struct Collider {
     pub friction: f32,
     /// The restitution coefficient of this collider.
     pub restitution: f32,
+    pub(crate) collision_groups: InteractionGroups,
     pub(crate) contact_graph_index: ColliderGraphIndex,
     pub(crate) proximity_graph_index: ColliderGraphIndex,
     pub(crate) proxy_index: usize,
@@ -255,6 +256,11 @@ impl Collider {
         &self.delta
     }
 
+    /// The collision groups used by this collider.
+    pub fn collision_groups(&self) -> InteractionGroups {
+        self.collision_groups
+    }
+
     /// The density of this collider.
     pub fn density(&self) -> f32 {
         self.density
@@ -300,6 +306,8 @@ pub struct ColliderBuilder {
     pub is_sensor: bool,
     /// The user-data of the collider beind built.
     pub user_data: u128,
+    /// The collision groups for the collider being built.
+    pub collision_groups: InteractionGroups,
 }
 
 impl ColliderBuilder {
@@ -313,6 +321,7 @@ impl ColliderBuilder {
             delta: Isometry::identity(),
             is_sensor: false,
             user_data: 0,
+            collision_groups: InteractionGroups::all(),
         }
     }
 
@@ -418,12 +427,21 @@ impl ColliderBuilder {
         0.5
     }
 
-    /// An arbitrary user-defined 128-bit integer associated to the colliders built by this builder.
+    /// Sets an arbitrary user-defined 128-bit integer associated to the colliders built by this builder.
     pub fn user_data(mut self, data: u128) -> Self {
         self.user_data = data;
         self
     }
 
+    /// Sets the collision groups used by this collider.
+    ///
+    /// Two colliders will interact iff. their collision groups are compatible.
+    /// See [InteractionGroups::test] for details.
+    pub fn collision_groups(mut self, groups: InteractionGroups) -> Self {
+        self.collision_groups = groups;
+        self
+    }
+
     /// Sets whether or not the collider built by this builder is a sensor.
     pub fn sensor(mut self, is_sensor: bool) -> Self {
         self.is_sensor = is_sensor;

src/geometry/interaction_groups.rs

@@ -0,0 +1,54 @@
+#[repr(transparent)]
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+/// Pairwise filtering using bit masks.
+///
+/// This filtering method is based on two 16-bit values:
+/// - The interaction groups (the 16 left-most bits of `self.0`).
+/// - The interaction mask (the 16 right-most bits of `self.0`).
+///
+/// An interaction is allowed between two filters `a` and `b` two conditions
+/// are met simultaneously:
+/// - The interaction groups of `a` has at least one bit set to `1` in common with the interaction mask of `b`.
+/// - The interaction groups of `b` has at least one bit set to `1` in common with the interaction mask of `a`.
+/// In other words, interactions are allowed between two filter iff. the following condition is met:
+/// ```rust
+/// ((self.0 >> 16) & rhs.0) != 0 && ((rhs.0 >> 16) & self.0) != 0
+/// ```
+pub struct InteractionGroups(pub u32);
+
+impl InteractionGroups {
+    /// Allow interaction with everything.
+    pub fn all() -> Self {
+        Self(u32::MAX)
+    }
+
+    /// Prevent all interactions.
+    pub fn none() -> Self {
+        Self(0)
+    }
+
+    /// Sets the group this filter is part of.
+    pub fn with_groups(self, groups: u16) -> Self {
+        Self((self.0 & 0x0000ffff) | ((groups as u32) << 16))
+    }
+
+    /// Sets the interaction mask of this filter.
+    pub fn with_mask(self, mask: u16) -> Self {
+        Self((self.0 & 0xffff0000) | (mask as u32))
+    }
+
+    /// Check if interactions should be allowed based on the interaction groups and mask.
+    ///
+    /// An interaction is allowed iff. the groups of `self` contain at least one bit set to 1 in common
+    /// with the mask of `rhs`, and vice-versa.
+    pub fn test(self, rhs: Self) -> bool {
+        ((self.0 >> 16) & rhs.0) != 0 && ((rhs.0 >> 16) & self.0) != 0
+    }
+}
+
+impl Default for InteractionGroups {
+    fn default() -> Self {
+        Self::all()
+    }
+}

src/geometry/mod.rs

@@ -70,6 +70,7 @@ pub(crate) use self::polyhedron_feature3d::PolyhedronFace;
 pub(crate) use self::waabb::{WRay, WAABB};
 pub(crate) use self::wquadtree::WQuadtree;
 //pub(crate) use self::z_order::z_cmp_floats;
+pub use self::interaction_groups::InteractionGroups;
 pub use self::shape::{Shape, ShapeType};
 
 mod ball;
@@ -97,6 +98,7 @@ mod waabb;
 mod wquadtree;
 //mod z_order;
 mod capsule;
+mod interaction_groups;
 #[cfg(feature = "dim3")]
 mod polygonal_feature_map;
 #[cfg(feature = "dim3")]

src/geometry/narrow_phase.rs

@@ -306,6 +306,11 @@ impl NarrowPhase {
                 return;
             }
 
+            if !co1.collision_groups.test(co2.collision_groups) {
+                // The collision is not allowed.
+                return;
+            }
+
             let dispatcher = DefaultProximityDispatcher;
             if pair.detector.is_none() {
                 // We need a redispatch for this detector.
@@ -329,69 +334,6 @@ impl NarrowPhase {
                 .unwrap()
                 .detect_proximity(context, events);
         });
-
-        /*
-        // First, group pairs.
-        // NOTE: the transmutes here are OK because the Vec are all cleared
-        // before we leave this method.
-        // We do this in order to avoid reallocating those vecs each time
-        // we compute the contacts. Unsafe is necessary because we can't just
-        // store a Vec<&mut ProximityPair> into the NarrowPhase struct without
-        // polluting the World with lifetimes.
-        let ball_ball_prox: &mut Vec<&mut ProximityPair> =
-            unsafe { std::mem::transmute(&mut self.ball_ball_prox) };
-        let shape_shape_prox: &mut Vec<&mut ProximityPair> =
-            unsafe { std::mem::transmute(&mut self.shape_shape_prox) };
-
-        let bodies = &bodies.bodies;
-
-        // FIXME: don't iterate through all the interactions.
-        for pair in &mut self.proximity_graph.interactions {
-            let co1 = &colliders[pair.pair.collider1];
-            let co2 = &colliders[pair.pair.collider2];
-
-            // FIXME: avoid lookup into bodies.
-            let rb1 = &bodies[co1.parent];
-            let rb2 = &bodies[co2.parent];
-
-            if (rb1.is_sleeping() || !rb1.is_dynamic()) && (rb2.is_sleeping() || !rb2.is_dynamic())
-            {
-                // No need to update this proximity because nothing moved.
-                continue;
-            }
-
-            match (co1.shape(), co2.shape()) {
-                (Shape::Ball(_), Shape::Ball(_)) => ball_ball_prox.push(pair),
-                _ => shape_shape_prox.push(pair),
-            }
-        }
-
-        par_chunks_mut!(ball_ball_prox, SIMD_WIDTH).for_each(|pairs| {
-            let context = ProximityDetectionContextSimd {
-                dispatcher: &DefaultProximityDispatcher,
-                prediction_distance,
-                colliders,
-                pairs,
-            };
-            context.pairs[0]
-                .detector
-                .detect_proximity_simd(context, events);
-        });
-
-        par_iter_mut!(shape_shape_prox).for_each(|pair| {
-            let context = ProximityDetectionContext {
-                dispatcher: &DefaultProximityDispatcher,
-                prediction_distance,
-                colliders,
-                pair,
-            };
-
-            context.pair.detector.detect_proximity(context, events);
-        });
-
-        ball_ball_prox.clear();
-        shape_shape_prox.clear();
-        */
     }
 
     pub(crate) fn compute_contacts(
@@ -417,6 +359,11 @@ impl NarrowPhase {
                 return;
             }
 
+            if !co1.collision_groups.test(co2.collision_groups) {
+                // The collision is not allowed.
+                return;
+            }
+
             let dispatcher = DefaultContactDispatcher;
             if pair.generator.is_none() {
                 // We need a redispatch for this generator.
@@ -440,69 +387,6 @@ impl NarrowPhase {
                 .unwrap()
                 .generate_contacts(context, events);
         });
-
-        /*
-        // First, group pairs.
-        // NOTE: the transmutes here are OK because the Vec are all cleared
-        // before we leave this method.
-        // We do this in order to avoid reallocating those vecs each time
-        // we compute the contacts. Unsafe is necessary because we can't just
-        // store a Vec<&mut ContactPair> into the NarrowPhase struct without
-        // polluting the World with lifetimes.
-        let ball_ball: &mut Vec<&mut ContactPair> =
-            unsafe { std::mem::transmute(&mut self.ball_ball) };
-        let shape_shape: &mut Vec<&mut ContactPair> =
-            unsafe { std::mem::transmute(&mut self.shape_shape) };
-
-        let bodies = &bodies.bodies;
-
-        // FIXME: don't iterate through all the interactions.
-        for pair in &mut self.contact_graph.interactions {
-            let co1 = &colliders[pair.pair.collider1];
-            let co2 = &colliders[pair.pair.collider2];
-
-            // FIXME: avoid lookup into bodies.
-            let rb1 = &bodies[co1.parent];
-            let rb2 = &bodies[co2.parent];
-
-            if (rb1.is_sleeping() || !rb1.is_dynamic()) && (rb2.is_sleeping() || !rb2.is_dynamic())
-            {
-                // No need to update this contact because nothing moved.
-                continue;
-            }
-
-            match (co1.shape(), co2.shape()) {
-                (Shape::Ball(_), Shape::Ball(_)) => ball_ball.push(pair),
-                _ => shape_shape.push(pair),
-            }
-        }
-
-        par_chunks_mut!(ball_ball, SIMD_WIDTH).for_each(|pairs| {
-            let context = ContactGenerationContextSimd {
-                dispatcher: &DefaultContactDispatcher,
-                prediction_distance,
-                colliders,
-                pairs,
-            };
-            context.pairs[0]
-                .generator
-                .generate_contacts_simd(context, events);
-        });
-
-        par_iter_mut!(shape_shape).for_each(|pair| {
-            let context = ContactGenerationContext {
-                dispatcher: &DefaultContactDispatcher,
-                prediction_distance,
-                colliders,
-                pair,
-            };
-
-            context.pair.generator.generate_contacts(context, events);
-        });
-
-        ball_ball.clear();
-        shape_shape.clear();
-        */
     }
 
     /// Retrieve all the interactions with at least one contact point, happening between two active bodies.