1 files changed, 8 insertions, 4 deletions
diff --git a/thirdparty/embree/common/math/quaternion.h b/thirdparty/embree/common/math/quaternion.h
index 080800efcd..78efccda72 100644
--- a/thirdparty/embree/common/math/quaternion.h
+++ b/thirdparty/embree/common/math/quaternion.h
@@ -242,13 +242,17 @@ namespace embree
     T cosTheta = dot(q0, q1_);
     QuaternionT<T> q1 = select(cosTheta < 0.f, -q1_, q1_);
     cosTheta          = select(cosTheta < 0.f, -cosTheta, cosTheta);
-    if (unlikely(all(cosTheta > 0.9995f))) {
-      return normalize(lerp(q0, q1, t));
-    }
+
+    // spherical linear interpolation
     const T phi = t * fastapprox::acos(cosTheta);
     T sinPhi, cosPhi;
     fastapprox::sincos(phi, sinPhi, cosPhi);
     QuaternionT<T> qperp = sinPhi * normalize(msub(cosTheta, q0, q1));
-    return msub(cosPhi, q0, qperp);
+    QuaternionT<T> qslerp = msub(cosPhi, q0, qperp);
+
+    // regular linear interpolation as fallback
+    QuaternionT<T> qlerp = normalize(lerp(q0, q1, t));
+
+    return select(cosTheta > 0.9995f, qlerp, qslerp);
   }
 }