From 88003c37d7bcbf25f79154dc88e06140d34cce16 Mon Sep 17 00:00:00 2001
From: SamGondelman <samuel_gondelman@alumni.brown.edu>
Date: Mon, 10 Jun 2019 16:44:17 -0700
Subject: [PATCH] fix physics assert

---
 libraries/physics/src/PhysicsEngine.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libraries/physics/src/PhysicsEngine.cpp b/libraries/physics/src/PhysicsEngine.cpp
index 976c547c5e..655edd4e13 100644
--- a/libraries/physics/src/PhysicsEngine.cpp
+++ b/libraries/physics/src/PhysicsEngine.cpp
@@ -35,7 +35,7 @@ static bool flipNormalsMyAvatarVsBackfacingTriangles(btManifoldPoint& cp,
         const btVector3* v = triShape->m_vertices1;
         btVector3 faceNormal = colObj1Wrap->getWorldTransform().getBasis() * btCross(v[1] - v[0], v[2] - v[0]);
         float nDotF = btDot(faceNormal, cp.m_normalWorldOnB);
-        if (nDotF <= 0.0f) {
+        if (nDotF <= 0.0f && faceNormal.length2() > EPSILON) {
             faceNormal.normalize();
             // flip the contact normal to be aligned with the face normal
             cp.m_normalWorldOnB += -2.0f * nDotF * faceNormal;