Merge pull request #67 from dimforge/determinism_apple_m1

Fix cross-platform determinism on the Apple M1 processor

examples3d/heightfield3.rs

@@ -1,4 +1,4 @@
-use na::{DMatrix, Point3, Vector3};
+use na::{ComplexField, DMatrix, Point3, Vector3};
 use rapier3d::dynamics::{JointSet, RigidBodyBuilder, RigidBodySet};
 use rapier3d::geometry::{ColliderBuilder, ColliderSet};
 use rapier_testbed3d::Testbed;
@@ -23,7 +23,11 @@ pub fn init_world(testbed: &mut Testbed) {
         } else {
             let x = i as f32 * ground_size.x / (nsubdivs as f32);
             let z = j as f32 * ground_size.z / (nsubdivs as f32);
-            x.sin() + z.cos()
+
+            // NOTE: make sure we use the sin/cos from simba to ensure
+            // cross-platform determinism of the example when the
+            // enhanced_determinism feature is enabled.
+            (<f32 as ComplexField>::sin(x) + <f32 as ComplexField>::cos(z))
         }
     });
 

examples3d/trimesh3.rs

@@ -1,4 +1,4 @@
-use na::Point3;
+use na::{ComplexField, Point3};
 use rapier3d::dynamics::{JointSet, RigidBodyBuilder, RigidBodySet};
 use rapier3d::geometry::{ColliderBuilder, ColliderSet};
 use rapier_testbed3d::Testbed;
@@ -30,7 +30,10 @@ pub fn init_world(testbed: &mut Testbed) {
     // so we switch z and y here and set a random altitude at each point.
     for p in vertices.iter_mut() {
         p.z = p.y;
-        p.y = (p.x.sin() + p.z.cos()) * ground_height;
+        // NOTE: make sure we use the sin/cos from simba to ensure
+        // cross-platform determinism of the example when the
+        // enhanced_determinism feature is enabled.
+        p.y = (<f32 as ComplexField>::sin(p.x) + <f32 as ComplexField>::cos(p.z)) * ground_height;
 
         if p.x.abs() == ground_size / 2.0 || p.z.abs() == ground_size / 2.0 {
             p.y = 10.0;

src/geometry/waabb.rs

@@ -105,7 +105,16 @@ impl WAABB {
     }
 
     pub fn dilate_by_factor(&mut self, factor: SimdFloat) {
-        let dilation = (self.maxs - self.mins) * factor;
+        // If some of the AABBs on this WAABB are invalid,
+        // don't, dilate them.
+        let is_valid = self.mins.x.simd_le(self.maxs.x);
+        let factor = factor.select(is_valid, SimdFloat::zero());
+
+        // NOTE: we multiply each by factor instead of doing
+        // (maxs - mins) * factor. That's to avoid overflows (and
+        // therefore NaNs if this WAABB contains some invalid
+        // AABBs initialised with f32::MAX
+        let dilation = self.maxs * factor - self.mins * factor;
         self.mins -= dilation;
         self.maxs += dilation;
     }