From 7740162ad85d112510812bab7df01a4cf951e648 Mon Sep 17 00:00:00 2001
From: Erwin Coumans
 <erwincoumans@erwincoumans-macbookpro2.roam.corp.google.com>
Date: Sat, 22 Dec 2018 16:38:40 -0800
Subject: [PATCH] apply gimpact versus rotated plane issue,thanks to
 @cameronwhite see
 https://github.com/cameronwhite/bullet3/commit/bd8bd11929097fabeda14657967fc96376099e62
 Fixes Issue 69

---
 .../Gimpact/btGImpactCollisionAlgorithm.cpp              | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/BulletCollision/Gimpact/btGImpactCollisionAlgorithm.cpp b/src/BulletCollision/Gimpact/btGImpactCollisionAlgorithm.cpp
index 4a1835d0d..d42644b81 100644
--- a/src/BulletCollision/Gimpact/btGImpactCollisionAlgorithm.cpp
+++ b/src/BulletCollision/Gimpact/btGImpactCollisionAlgorithm.cpp
@@ -50,10 +50,11 @@ public:
 
 	void get_plane_equation_transformed(const btTransform& trans, btVector4& equation) const
 	{
-		equation[0] = trans.getBasis().getRow(0).dot(m_planeNormal);
-		equation[1] = trans.getBasis().getRow(1).dot(m_planeNormal);
-		equation[2] = trans.getBasis().getRow(2).dot(m_planeNormal);
-		equation[3] = trans.getOrigin().dot(m_planeNormal) + m_planeConstant;
+		const btVector3 normal = trans.getBasis() * m_planeNormal;
+		equation[0] = normal[0];
+		equation[1] = normal[1];
+		equation[2] = normal[2];
+		equation[3] = normal.dot(trans * (m_planeConstant * m_planeNormal));
 	}
 };