From 0117233ed4482d2b6592a9a7319319844be985c6 Mon Sep 17 00:00:00 2001
From: Andrew Meadows <andrew@highfidelity.io>
Date: Wed, 12 Nov 2014 15:19:33 -0800
Subject: [PATCH] add ThreadSafeDynamicsWorld pure virtual interface

---
 .../physics/src/ThreadSafeDynamicsWorld.cpp   | 83 +++++++++++++++++++
 .../physics/src/ThreadSafeDynamicsWorld.h     | 44 ++++++++++
 2 files changed, 127 insertions(+)
 create mode 100644 libraries/physics/src/ThreadSafeDynamicsWorld.cpp
 create mode 100644 libraries/physics/src/ThreadSafeDynamicsWorld.h

diff --git a/libraries/physics/src/ThreadSafeDynamicsWorld.cpp b/libraries/physics/src/ThreadSafeDynamicsWorld.cpp
new file mode 100644
index 0000000000..54bea0fff5
--- /dev/null
+++ b/libraries/physics/src/ThreadSafeDynamicsWorld.cpp
@@ -0,0 +1,83 @@
+/*
+ * Bullet Continuous Collision Detection and Physics Library
+ * Copyright (c) 2003-2009 Erwin Coumans  http://bulletphysics.org
+ *
+ * This software is provided 'as-is', without any express or implied warranty.
+ * In no event will the authors be held liable for any damages arising from the use of this software.
+ * Permission is granted to anyone to use this software for any purpose, 
+ * including commercial applications, and to alter it and redistribute it freely, 
+ * subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ *
+ * Copied and modified from btDiscreteDynamicsWorld.cpp by AndrewMeadows on 2014.11.12.
+ * */
+
+#include "ThreadSafeDynamicsWorld.h"
+
+ThreadSafeDynamicsWorld::ThreadSafeDynamicsWorld(
+        btDispatcher* dispatcher,
+        btBroadphaseInterface* pairCache,
+        btConstraintSolver* constraintSolver,
+        btCollisionConfiguration* collisionConfiguration)
+    :   btDiscreteDynamicsWorld(dispatcher, pairCache, constraintSolver, collisionConfiguration) {
+}
+
+void ThreadSafeDynamicsWorld::synchronizeMotionStates() {
+    if (tryLock()) {
+        btDiscreteDynamicsWorld::synchronizeMotionStates();
+        unlock();
+    }
+}
+
+int	ThreadSafeDynamicsWorld::stepSimulation( btScalar timeStep, int maxSubSteps, btScalar fixedTimeStep) {
+	int subSteps = 0;
+	if (maxSubSteps) {
+		//fixed timestep with interpolation
+		m_fixedTimeStep = fixedTimeStep;
+		m_localTime += timeStep;
+		if (m_localTime >= fixedTimeStep)
+		{
+			subSteps = int( m_localTime / fixedTimeStep);
+			m_localTime -= subSteps * fixedTimeStep;
+		}
+	} else {
+		//variable timestep
+		fixedTimeStep = timeStep;
+		m_localTime = m_latencyMotionStateInterpolation ? 0 : timeStep;
+		m_fixedTimeStep = 0;
+		if (btFuzzyZero(timeStep))
+		{
+			subSteps = 0;
+			maxSubSteps = 0;
+		} else
+		{
+			subSteps = 1;
+			maxSubSteps = 1;
+		}
+	}
+
+	/*//process some debugging flags
+	if (getDebugDrawer()) {
+		btIDebugDraw* debugDrawer = getDebugDrawer ();
+		gDisableDeactivation = (debugDrawer->getDebugMode() & btIDebugDraw::DBG_NoDeactivation) != 0;
+	}*/
+	if (subSteps) {
+		//clamp the number of substeps, to prevent simulation grinding spiralling down to a halt
+		int clampedSimulationSteps = (subSteps > maxSubSteps)? maxSubSteps : subSteps;
+
+		saveKinematicState(fixedTimeStep*clampedSimulationSteps);
+
+		applyGravity();
+
+		for (int i=0;i<clampedSimulationSteps;i++) {
+			internalSingleStepSimulation(fixedTimeStep);
+		}
+	}
+
+    synchronizeMotionStates();
+	clearForces();
+	return subSteps;
+}
diff --git a/libraries/physics/src/ThreadSafeDynamicsWorld.h b/libraries/physics/src/ThreadSafeDynamicsWorld.h
new file mode 100644
index 0000000000..0f7961044e
--- /dev/null
+++ b/libraries/physics/src/ThreadSafeDynamicsWorld.h
@@ -0,0 +1,44 @@
+/*
+ * Bullet Continuous Collision Detection and Physics Library
+ * Copyright (c) 2003-2009 Erwin Coumans  http://bulletphysics.org
+ *
+ * This software is provided 'as-is', without any express or implied warranty.
+ * In no event will the authors be held liable for any damages arising from the use of this software.
+ * Permission is granted to anyone to use this software for any purpose, 
+ * including commercial applications, and to alter it and redistribute it freely, 
+ * subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ *
+ * Copied and modified from btDiscreteDynamicsWorld.h by AndrewMeadows on 2014.11.12.
+ * */
+
+#ifndef hifi_ThreadSafeDynamicsWorld_h
+#define hifi_ThreadSafeDynamicsWorld_h
+
+#include <BulletDynamics/Dynamics/btDiscreteDynamicsWorld.h>
+
+ATTRIBUTE_ALIGNED16(class) ThreadSafeDynamicsWorld : public btDiscreteDynamicsWorld
+{
+public:
+    BT_DECLARE_ALIGNED_ALLOCATOR();
+
+    ThreadSafeDynamicsWorld(
+            btDispatcher* dispatcher,
+            btBroadphaseInterface* pairCache,
+            btConstraintSolver* constraintSolver,
+            btCollisionConfiguration* collisionConfiguration);
+
+    // virtual overrides of btDiscreteDynamicsWorld
+    int stepSimulation( btScalar timeStep, int maxSubSteps=1, btScalar fixedTimeStep=btScalar(1.)/btScalar(60.));
+    void synchronizeMotionStates();
+
+    /// \return true if lock succeeds
+    virtual bool tryLock() = 0;
+
+    virtual void unlock() = 0;
+};
+
+#endif // hifi_ThreadSafeDynamicsWorld_h