Add solver flags for controlling whether or not some contacts should be taken into account by the constraints solver.

7 files changed, 76 insertions, 12 deletions

diff --git a/src/geometry/collider.rs b/src/geometry/collider.rs
index 7147e95..f53d75a 100644
--- a/src/geometry/collider.rs
+++ b/src/geometry/collider.rs
@@ -204,6 +204,7 @@ pub struct Collider {
     /// The restitution coefficient of this collider.
     pub restitution: f32,
     pub(crate) collision_groups: InteractionGroups,
+    pub(crate) solver_groups: InteractionGroups,
     pub(crate) contact_graph_index: ColliderGraphIndex,
     pub(crate) proximity_graph_index: ColliderGraphIndex,
     pub(crate) proxy_index: usize,
@@ -261,6 +262,11 @@ impl Collider {
         self.collision_groups
     }
 
+    /// The solver groups used by this collider.
+    pub fn solver_groups(&self) -> InteractionGroups {
+        self.solver_groups
+    }
+
     /// The density of this collider.
     pub fn density(&self) -> f32 {
         self.density
@@ -304,10 +310,12 @@ pub struct ColliderBuilder {
     pub delta: Isometry<f32>,
     /// Is this collider a sensor?
     pub is_sensor: bool,
-    /// The user-data of the collider beind built.
+    /// The user-data of the collider being built.
     pub user_data: u128,
     /// The collision groups for the collider being built.
     pub collision_groups: InteractionGroups,
+    /// The solver groups for the collider being built.
+    pub solver_groups: InteractionGroups,
 }
 
 impl ColliderBuilder {
@@ -322,6 +330,7 @@ impl ColliderBuilder {
             is_sensor: false,
             user_data: 0,
             collision_groups: InteractionGroups::all(),
+            solver_groups: InteractionGroups::all(),
         }
     }
 
@@ -442,6 +451,15 @@ impl ColliderBuilder {
         self
     }
 
+    /// Sets the solver groups used by this collider.
+    ///
+    /// Forces between two colliders in contact will be computed iff their solver groups are
+    /// compatible. See [InteractionGroups::test] for details.
+    pub fn solver_groups(mut self, groups: InteractionGroups) -> Self {
+        self.solver_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;
@@ -523,6 +541,8 @@ impl ColliderBuilder {
             contact_graph_index: InteractionGraph::<Contact>::invalid_graph_index(),
             proximity_graph_index: InteractionGraph::<Proximity>::invalid_graph_index(),
             proxy_index: crate::INVALID_USIZE,
+            collision_groups: self.collision_groups,
+            solver_groups: self.solver_groups,
             user_data: self.user_data,
         }
     }
diff --git a/src/geometry/contact.rs b/src/geometry/contact.rs
index d211cf1..1f50e43 100644
--- a/src/geometry/contact.rs
+++ b/src/geometry/contact.rs
@@ -9,6 +9,16 @@ use {
     simba::simd::SimdValue,
 };
 
+bitflags::bitflags! {
+    #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+    /// Flags affecting the behavior of the constraints solver for a given contact manifold.
+    pub struct SolverFlags: u32 {
+        /// The constraint solver will take this contact manifold into
+        /// account for force computation.
+        const COMPUTE_FORCES = 0b01;
+    }
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
 /// The type local linear approximation of the neighborhood of a pair contact points on two shapes
@@ -206,6 +216,7 @@ impl ContactPair {
     pub(crate) fn single_manifold<'a, 'b>(
         &'a mut self,
         colliders: &'b ColliderSet,
+        flags: SolverFlags,
     ) -> (
         &'b Collider,
         &'b Collider,
@@ -216,7 +227,7 @@ impl ContactPair {
         let coll2 = &colliders[self.pair.collider2];
 
         if self.manifolds.len() == 0 {
-            let manifold = ContactManifold::from_colliders(self.pair, coll1, coll2);
+            let manifold = ContactManifold::from_colliders(self.pair, coll1, coll2, flags);
             self.manifolds.push(manifold);
         }
 
@@ -288,6 +299,8 @@ pub struct ContactManifold {
     /// The relative position between the second collider and its parent at the time the
     /// contact points were generated.
     pub delta2: Isometry<f32>,
+    /// Flags used to control some aspects of the constraints solver for this contact manifold.
+    pub solver_flags: SolverFlags,
 }
 
 impl ContactManifold {
@@ -299,6 +312,7 @@ impl ContactManifold {
         delta2: Isometry<f32>,
         friction: f32,
         restitution: f32,
+        solver_flags: SolverFlags,
     ) -> ContactManifold {
         Self {
             #[cfg(feature = "dim2")]
@@ -319,6 +333,7 @@ impl ContactManifold {
             delta2,
             constraint_index: 0,
             position_constraint_index: 0,
+            solver_flags,
         }
     }
 
@@ -342,11 +357,17 @@ impl ContactManifold {
             delta2: self.delta2,
             constraint_index: self.constraint_index,
             position_constraint_index: self.position_constraint_index,
+            solver_flags: self.solver_flags,
         }
     }
 
-    pub(crate) fn from_colliders(pair: ColliderPair, coll1: &Collider, coll2: &Collider) -> Self {
-        Self::with_subshape_indices(pair, coll1, coll2, 0, 0)
+    pub(crate) fn from_colliders(
+        pair: ColliderPair,
+        coll1: &Collider,
+        coll2: &Collider,
+        flags: SolverFlags,
+    ) -> Self {
+        Self::with_subshape_indices(pair, coll1, coll2, 0, 0, flags)
     }
 
     pub(crate) fn with_subshape_indices(
@@ -355,6 +376,7 @@ impl ContactManifold {
         coll2: &Collider,
         subshape1: usize,
         subshape2: usize,
+        solver_flags: SolverFlags,
     ) -> Self {
         Self::new(
             pair,
@@ -364,6 +386,7 @@ impl ContactManifold {
             *coll2.position_wrt_parent(),
             (coll1.friction + coll2.friction) * 0.5,
             (coll1.restitution + coll2.restitution) * 0.5,
+            solver_flags,
         )
     }
 
diff --git a/src/geometry/contact_generator/contact_generator.rs b/src/geometry/contact_generator/contact_generator.rs
index b034760..728794d 100644
--- a/src/geometry/contact_generator/contact_generator.rs
+++ b/src/geometry/contact_generator/contact_generator.rs
@@ -1,5 +1,6 @@
 use crate::geometry::{
     Collider, ColliderSet, ContactDispatcher, ContactEvent, ContactManifold, ContactPair, Shape,
+    SolverFlags,
 };
 use crate::math::Isometry;
 #[cfg(feature = "simd-is-enabled")]
@@ -26,8 +27,9 @@ impl ContactPhase {
             Self::NearPhase(gen) => (gen.generate_contacts)(&mut context),
             Self::ExactPhase(gen) => {
                 // Build the primitive context from the non-primitive context and dispatch.
-                let (collider1, collider2, manifold, workspace) =
-                    context.pair.single_manifold(context.colliders);
+                let (collider1, collider2, manifold, workspace) = context
+                    .pair
+                    .single_manifold(context.colliders, context.solver_flags);
                 let mut context2 = PrimitiveContactGenerationContext {
                     prediction_distance: context.prediction_distance,
                     collider1,
@@ -85,9 +87,11 @@ impl ContactPhase {
                     [Option<&mut (dyn Any + Send + Sync)>; SIMD_WIDTH],
                 > = ArrayVec::new();
 
-                for pair in context.pairs.iter_mut() {
+                for (pair, solver_flags) in
+                    context.pairs.iter_mut().zip(context.solver_flags.iter())
+                {
                     let (collider1, collider2, manifold, workspace) =
-                        pair.single_manifold(context.colliders);
+                        pair.single_manifold(context.colliders, *solver_flags);
                     colliders_arr.push((collider1, collider2));
                     manifold_arr.push(manifold);
                     workspace_arr.push(workspace);
@@ -188,6 +192,7 @@ pub struct ContactGenerationContext<'a> {
     pub prediction_distance: f32,
     pub colliders: &'a ColliderSet,
     pub pair: &'a mut ContactPair,
+    pub solver_flags: SolverFlags,
 }
 
 #[cfg(feature = "simd-is-enabled")]
@@ -196,6 +201,7 @@ pub struct ContactGenerationContextSimd<'a, 'b> {
     pub prediction_distance: f32,
     pub colliders: &'a ColliderSet,
     pub pairs: &'a mut [&'b mut ContactPair],
+    pub solver_flags: &'a [SolverFlags],
 }
 
 #[derive(Copy, Clone)]
diff --git a/src/geometry/contact_generator/heightfield_shape_contact_generator.rs b/src/geometry/contact_generator/heightfield_shape_contact_generator.rs
index 9224d4e..f291fa0 100644
--- a/src/geometry/contact_generator/heightfield_shape_contact_generator.rs
+++ b/src/geometry/contact_generator/heightfield_shape_contact_generator.rs
@@ -104,6 +104,7 @@ fn do_generate_contacts(
     let manifolds = &mut ctxt.pair.manifolds;
     let prediction_distance = ctxt.prediction_distance;
     let dispatcher = ctxt.dispatcher;
+    let solver_flags = ctxt.solver_flags;
     let shape_type2 = collider2.shape().shape_type();
 
     heightfield1.map_elements_in_local_aabb(&ls_aabb2, &mut |i, part1, _| {
@@ -131,8 +132,14 @@ fn do_generate_contacts(
                     timestamp: new_timestamp,
                     workspace: workspace2,
                 };
-                let manifold =
-                    ContactManifold::with_subshape_indices(coll_pair, collider1, collider2, i, 0);
+                let manifold = ContactManifold::with_subshape_indices(
+                    coll_pair,
+                    collider1,
+                    collider2,
+                    i,
+                    0,
+                    solver_flags,
+                );
                 manifolds.push(manifold);
 
                 entry.insert(sub_detector)
diff --git a/src/geometry/contact_generator/trimesh_shape_contact_generator.rs b/src/geometry/contact_generator/trimesh_shape_contact_generator.rs
index 502658d..9474516 100644
--- a/src/geometry/contact_generator/trimesh_shape_contact_generator.rs
+++ b/src/geometry/contact_generator/trimesh_shape_contact_generator.rs
@@ -149,6 +149,7 @@ fn do_generate_contacts(
                     collider2,
                     *triangle_id,
                     0,
+                    ctxt.solver_flags,
                 )
             } else {
                 // We already have a manifold for this triangle.
diff --git a/src/geometry/mod.rs b/src/geometry/mod.rs
index 4055d43..9da35d9 100644
--- a/src/geometry/mod.rs
+++ b/src/geometry/mod.rs
@@ -5,7 +5,7 @@ pub use self::capsule::Capsule;
 pub use self::collider::{Collider, ColliderBuilder, ColliderShape};
 pub use self::collider_set::{ColliderHandle, ColliderSet};
 pub use self::contact::{
-    Contact, ContactKinematics, ContactManifold, ContactPair, KinematicsCategory,
+    Contact, ContactKinematics, ContactManifold, ContactPair, KinematicsCategory, SolverFlags,
 };
 pub use self::contact_generator::{ContactDispatcher, DefaultContactDispatcher};
 #[cfg(feature = "dim2")]
diff --git a/src/geometry/narrow_phase.rs b/src/geometry/narrow_phase.rs
index 5bcdcdb..290d55f 100644
--- a/src/geometry/narrow_phase.rs
+++ b/src/geometry/narrow_phase.rs
@@ -15,7 +15,7 @@ use crate::geometry::proximity_detector::{
 //};
 use crate::geometry::{
     BroadPhasePairEvent, ColliderGraphIndex, ColliderHandle, ContactEvent, ProximityEvent,
-    ProximityPair, RemovedCollider,
+    ProximityPair, RemovedCollider, SolverFlags,
 };
 use crate::geometry::{ColliderSet, ContactManifold, ContactPair, InteractionGraph};
 //#[cfg(feature = "simd-is-enabled")]
@@ -374,11 +374,18 @@ impl NarrowPhase {
                 pair.generator_workspace = workspace;
             }
 
+            let solver_flags = if co1.solver_groups.test(co2.solver_groups) {
+                SolverFlags::COMPUTE_FORCES
+            } else {
+                SolverFlags::empty()
+            };
+
             let context = ContactGenerationContext {
                 dispatcher: &dispatcher,
                 prediction_distance,
                 colliders,
                 pair,
+                solver_flags,
             };
 
             context