Use Box<Option<MassProperties>> instead to save on memory

1 files changed, 10 insertions, 6 deletions

diff --git a/src/geometry/collider.rs b/src/geometry/collider.rs
index 68caf42..2691a1a 100644
--- a/src/geometry/collider.rs
+++ b/src/geometry/collider.rs
@@ -49,7 +49,8 @@ impl ColliderFlags {
 pub struct Collider {
     shape: SharedShape,
     density: Real,
-    mass_properties: MassProperties,
+    /// If None, use [`Self::density`] and [`SharedShape::mass_properties`].
+    mass_properties: Option<Box<MassProperties>>,
     pub(crate) flags: ColliderFlags,
     pub(crate) solver_flags: SolverFlags,
     pub(crate) parent: RigidBodyHandle,
@@ -135,9 +136,12 @@ impl Collider {
     //     aabb1.merged(&aabb2)
     // }
 
-    /// Read the local-space mass properties of this collider.
-    pub fn mass_properties(&self) -> &MassProperties {
-        &self.mass_properties
+    /// Compute the local-space mass properties of this collider.
+    pub fn mass_properties(&self) -> MassProperties {
+        match &self.mass_properties {
+            Some(mass_properties) => **mass_properties,
+            None => self.shape.mass_properties(self.density),
+        }
     }
 }
 
@@ -559,7 +563,7 @@ impl ColliderBuilder {
     pub fn build(&self) -> Collider {
         let (density, mass_properties);
         if let Some(mp) = self.mass_properties {
-            mass_properties = mp;
+            mass_properties = Some(Box::new(mp));
 
             let volume = volume(&self.shape);
             density = if volume == 0.0 || mp.inv_mass == 0.0 {
@@ -569,7 +573,7 @@ impl ColliderBuilder {
             };
         } else {
             density = self.get_density();
-            mass_properties = self.shape.mass_properties(density);
+            mass_properties = None;
         }
 
         let mut flags = ColliderFlags::empty();