Stub some joint concepts in physics

common/src/abstractions/assets.rs

@@ -8,7 +8,7 @@ use std::{
 pub use exporters::*;
 pub use importers::*;
 
-use crate::{FastHashMap, FileSystemError, Guid, impl_from_error, StreamError, StringName, ToVirtualPath, VirtualPath};
+use crate::{FastHashMap, FileSystemError, Guid, StreamError, StringName, ToVirtualPath, VirtualPath};
 
 /// Represents a reference to an asset that can either be loaded or unloaded.
 ///

common/src/collections.rs

@@ -5,6 +5,8 @@ use std::{
   hash::BuildHasherDefault,
 };
 
+pub use smallvec::{smallvec, SmallVec};
+
 pub use anymap::*;
 pub use arena::*;
 pub use graphs::*;
@@ -13,7 +15,6 @@ pub use multimap::*;
 pub use priorityqueue::*;
 pub use quadtree::*;
 pub use ringbuffer::*;
-pub use smallvec::{smallvec, SmallVec};
 pub use spatialhash::*;
 
 mod anymap;
@@ -32,7 +33,7 @@ pub type FastHashSet<K> = HashSet<K, BuildHasherDefault<rustc_hash::FxHasher>>;
 /// A faster hash map that is not resilient to DoS attacks.
 pub type FastHashMap<K, V> = HashMap<K, V, BuildHasherDefault<rustc_hash::FxHasher>>;
 
-/// A faster multi-map that is not resilient to DoS attacks.
+/// A faster multimap that is not resilient to DoS attacks.
 pub type FastMultiMap<K, V> = MultiMap<K, V, FastHashMap<K, BuildHasherDefault<rustc_hash::FxHasher>>>;
 
 /// A faster any-map that is not resilient to DoS attacks.

common/src/maths/linear.rs

@@ -2,11 +2,11 @@
 
 use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 
+pub use glam::*;
+
 pub use aabb::*;
 pub use bsp::*;
-pub use fields::*;
 pub use frustum::*;
-pub use glam::*;
 pub use planes::*;
 pub use rays::*;
 pub use scalars::*;
@@ -17,7 +17,6 @@ use super::*;
 
 mod aabb;
 mod bsp;
-mod fields;
 mod frustum;
 mod planes;
 mod rays;

common/src/maths/linear/frustum.rs

@@ -1,6 +1,7 @@
-use super::*;
 use crate::reinterpret_cast;
 
+use super::*;
+
 /// A frustum in 3-space.
 #[repr(C)]
 #[derive(Default, Clone, Debug)]
@@ -109,16 +110,22 @@ impl Frustum {
   }
 
   /// Converts this frustum to an array of planes.
+  ///
+  /// The order is Near, Far, Left, Right, Top, Bottom.
   pub fn into_array(self) -> [Plane; 6] {
     [self.near, self.far, self.left, self.right, self.top, self.bottom]
   }
 
   /// Converts this frustum to an array of planes.
+  ///
+  /// The order is Near, Far, Left, Right, Top, Bottom.
   pub fn to_array(&self) -> [Plane; 6] {
     [self.near, self.far, self.left, self.right, self.top, self.bottom]
   }
 
   /// Converts this frustum to a slice of planes.
+  ///
+  /// The order is Near, Far, Left, Right, Top, Bottom.
   pub fn as_slice(&self) -> &[Plane; 6] {
     unsafe { reinterpret_cast(self) }
   }

common/src/maths/linear/sdf.rs

@@ -15,11 +15,6 @@ pub trait SDF {
 
   /// Computes the distance to the shape at the given point.
   fn distance_to(&self, point: Self::Vector) -> <Self::Vector as Vector>::Scalar;
-
-  /// Converts this signed distance field into an evaluated field structure.
-  fn to_field(&self, _size: Self::Vector, _step: Self::Vector) -> Field<Self::Vector> {
-    todo!()
-  }
 }
 
 impl SDF for Circle {

modules/physics/src/lib.rs

@@ -9,6 +9,7 @@ mod simplex;
 common::impl_arena_index!(ColliderId, "Identifies a collider.");
 common::impl_arena_index!(BodyId, "Identifies a physics body.");
 common::impl_arena_index!(EffectorId, "Identifies an effector.");
+common::impl_arena_index!(JointId, "Identifies a joint.");
 
 common::impl_server!(PhysicsEngine, PhysicsBackend);
 
@@ -111,6 +112,15 @@ pub trait PhysicsWorld2D: PhysicsWorld {
   fn effector_set_strength(&self, effector: EffectorId, strength: f32);
   fn effector_get_strength(&self, effector: EffectorId) -> f32;
   fn effector_delete(&self, effector: EffectorId);
+
+  // joints
+  fn joint_create(&self) -> JointId;
+  fn joint_attach(&self, joint: JointId, body_a: BodyId, body_b: BodyId);
+  fn joint_detach(&self, joint: JointId);
+  fn joint_get_bodies(&self, joint: JointId) -> (BodyId, BodyId);
+  fn joint_set_anchor(&self, joint: JointId, anchor: Vec2);
+  fn joint_get_anchor(&self, joint: JointId) -> Vec2;
+  fn joint_delete(&self, joint: JointId);
 }
 
 /// A world of 3D physics.

modules/physics/src/simplex/world2d.rs

@@ -11,6 +11,7 @@ pub struct SimplexWorld2D {
   bodies: RwLock<Arena<BodyId, Body>>,
   colliders: RwLock<Arena<ColliderId, Collider>>,
   effectors: RwLock<Arena<EffectorId, Effector>>,
+  joints: RwLock<Arena<JointId, Joint>>,
 }
 
 /// Internal settings for a physics world.
@@ -82,6 +83,13 @@ enum EffectorShape {
   Cylinder { radius: f32, height: f32 },
 }
 
+/// A joint in the 2d physics world.
+struct Joint {
+  body_a: Option<BodyId>,
+  body_b: Option<BodyId>,
+  anchor: Vec2,
+}
+
 impl Default for Settings {
   fn default() -> Self {
     Self {
@@ -615,6 +623,69 @@ impl PhysicsWorld2D for SimplexWorld2D {
 
     effectors.remove(effector);
   }
+
+  #[profiling]
+  fn joint_create(&self) -> JointId {
+    let mut joints = self.joints.write().unwrap();
+
+    joints.insert(Joint {
+      body_a: None,
+      body_b: None,
+      anchor: Vec2::ZERO,
+    })
+  }
+
+  #[profiling]
+  fn joint_attach(&self, joint: JointId, body_a: BodyId, body_b: BodyId) {
+    let mut joints = self.joints.write().unwrap();
+
+    if let Some(joint) = joints.get_mut(joint) {
+      joint.body_a = Some(body_a);
+      joint.body_b = Some(body_b);
+    }
+  }
+
+  #[profiling]
+  fn joint_detach(&self, joint: JointId) {
+    let mut joints = self.joints.write().unwrap();
+
+    if let Some(joint) = joints.get_mut(joint) {
+      joint.body_a = None;
+      joint.body_b = None;
+    }
+  }
+
+  #[profiling]
+  fn joint_get_bodies(&self, joint: JointId) -> (BodyId, BodyId) {
+    let joints = self.joints.read().unwrap();
+
+    joints.get(joint).map_or((BodyId::default(), BodyId::default()), |it| {
+      (it.body_a.unwrap_or_default(), it.body_b.unwrap_or_default())
+    })
+  }
+
+  #[profiling]
+  fn joint_set_anchor(&self, joint: JointId, anchor: Vec2) {
+    let mut joints = self.joints.write().unwrap();
+
+    if let Some(joint) = joints.get_mut(joint) {
+      joint.anchor = anchor;
+    }
+  }
+
+  #[profiling]
+  fn joint_get_anchor(&self, joint: JointId) -> Vec2 {
+    let joints = self.joints.read().unwrap();
+
+    joints.get(joint).map_or(Vec2::ZERO, |it| it.anchor)
+  }
+
+  #[profiling]
+  fn joint_delete(&self, joint: JointId) {
+    let mut joints = self.joints.write().unwrap();
+
+    joints.remove(joint);
+  }
 }
 
 #[cfg(test)]
@@ -648,4 +719,17 @@ mod tests {
 
     assert_eq!(world.body_get_velocity(body_id), Vec2::ZERO);
   }
+
+  #[test]
+  fn it_should_create_a_simple_joint() {
+    let world = SimplexWorld2D::default();
+    let body1 = world.body_create(BodyKind::Kinematic, Vec2::ZERO);
+    let body2 = world.body_create(BodyKind::Kinematic, Vec2::ZERO);
+
+    let joint = world.joint_create();
+
+    world.joint_attach(joint, body1, body2);
+
+    assert_eq!(world.joint_get_bodies(joint), (body1, body2));
+  }
 }