From 62177ebb30a55a1cb8b62360ee0aa70056aa903c Mon Sep 17 00:00:00 2001
From: Andrei Kortunov <andrei.kortunov@yandex.ru>
Date: Tue, 26 Sep 2017 21:19:53 +0400
Subject: [PATCH] Move physics framerate from setting to environment variable

---
 apps/openmw/mwphysics/physicssystem.cpp       | 30 ++++++++++++-------
 apps/openmw/mwphysics/physicssystem.hpp       |  2 ++
 .../reference/modding/settings/physics.rst    | 13 --------
 files/settings-default.cfg                    |  4 ---
 4 files changed, 22 insertions(+), 27 deletions(-)
 delete mode 100644 docs/source/reference/modding/settings/physics.rst

diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index 068ff3186..887189a85 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -1,5 +1,6 @@
 #include "physicssystem.hpp"
 
+#include <iostream>
 #include <stdexcept>
 
 #include <osg/Group>
@@ -24,7 +25,6 @@
 #include <components/esm/loadgmst.hpp>
 #include <components/sceneutil/positionattitudetransform.hpp>
 #include <components/sceneutil/unrefqueue.hpp>
-#include <components/settings/settings.hpp>
 
 #include <components/nifosg/particle.hpp> // FindRecIndexVisitor
 
@@ -684,6 +684,7 @@ namespace MWPhysics
         , mWaterHeight(0)
         , mWaterEnabled(false)
         , mParentNode(parentNode)
+        , mPhysicsDt(1.f / 60.f)
     {
         mResourceSystem->addResourceManager(mShapeManager.get());
 
@@ -696,6 +697,20 @@ namespace MWPhysics
         // Don't update AABBs of all objects every frame. Most objects in MW are static, so we don't need this.
         // Should a "static" object ever be moved, we have to update its AABB manually using DynamicsWorld::updateSingleAabb.
         mCollisionWorld->setForceUpdateAllAabbs(false);
+
+        // Check if a user decided to override a physics system FPS
+        const char* env = getenv("OPENMW_PHYSICS_FPS");
+        if (env)
+        {
+            std::string str(env);
+
+            float physFramerate = std::atof(env);
+            if (physFramerate > 0)
+            {
+                mPhysicsDt = 1.f / physFramerate;
+                std::cerr << "Warning: physics framerate was overriden (a new value is " << physFramerate << ")."  << std::endl;
+            }
+        }
     }
 
     PhysicsSystem::~PhysicsSystem()
@@ -1359,16 +1374,11 @@ namespace MWPhysics
 
         mTimeAccum += dt;
 
-        static const float physFramerate = Settings::Manager::getFloat("physics framerate", "Physics");
-
-        // Allow to use a physics framerate between 10 and 60 FPS
-        static const float physicsDt = 1.f / std::max(10.f, std::min(60.f, physFramerate));
-
         const int maxAllowedSteps = 20;
-        int numSteps = mTimeAccum / (physicsDt);
+        int numSteps = mTimeAccum / (mPhysicsDt);
         numSteps = std::min(numSteps, maxAllowedSteps);
 
-        mTimeAccum -= numSteps * physicsDt;
+        mTimeAccum -= numSteps * mPhysicsDt;
 
         if (numSteps)
         {
@@ -1417,7 +1427,7 @@ namespace MWPhysics
             bool positionChanged = false;
             for (int i=0; i<numSteps; ++i)
             {
-                position = MovementSolver::move(position, physicActor->getPtr(), physicActor, iter->second, physicsDt,
+                position = MovementSolver::move(position, physicActor->getPtr(), physicActor, iter->second, mPhysicsDt,
                                                 flying, waterlevel, slowFall, mCollisionWorld, mStandingCollisions);
                 if (position != physicActor->getPosition())
                     positionChanged = true;
@@ -1426,7 +1436,7 @@ namespace MWPhysics
             if (positionChanged)
                 mCollisionWorld->updateSingleAabb(physicActor->getCollisionObject());
 
-            float interpolationFactor = mTimeAccum / physicsDt;
+            float interpolationFactor = mTimeAccum / mPhysicsDt;
             osg::Vec3f interpolated = position * interpolationFactor + physicActor->getPreviousPosition() * (1.f - interpolationFactor);
 
             float heightDiff = position.z() - oldHeight;
diff --git a/apps/openmw/mwphysics/physicssystem.hpp b/apps/openmw/mwphysics/physicssystem.hpp
index aaf55e2b6..3ef9990f5 100644
--- a/apps/openmw/mwphysics/physicssystem.hpp
+++ b/apps/openmw/mwphysics/physicssystem.hpp
@@ -220,6 +220,8 @@ namespace MWPhysics
 
             osg::ref_ptr<osg::Group> mParentNode;
 
+            float mPhysicsDt;
+
             PhysicsSystem (const PhysicsSystem&);
             PhysicsSystem& operator= (const PhysicsSystem&);
     };
diff --git a/docs/source/reference/modding/settings/physics.rst b/docs/source/reference/modding/settings/physics.rst
deleted file mode 100644
index e4f970a79..000000000
--- a/docs/source/reference/modding/settings/physics.rst
+++ /dev/null
@@ -1,13 +0,0 @@
-Physics Settings
-################
-
-physics framerate
----------------
-
-:Type:		floating point
-:Range:		10.0 to 60.0
-:Default:	60.0
-
-Allows to set how frequently an engine will do physics calculations. A default value is 60 times per second.
-This setting allows developers with low-clocked CPUs to test an engine.
-Changing from default value can lead to physics bugs. Change this setting on your own risk, and reset a value to default before filling a physics-related bugreport!
diff --git a/files/settings-default.cfg b/files/settings-default.cfg
index f4c7f0a4a..aec667a9c 100644
--- a/files/settings-default.cfg
+++ b/files/settings-default.cfg
@@ -277,10 +277,6 @@ camera y multiplier = 1.0
 # Invert the vertical axis while not in GUI mode.
 invert y axis = false
 
-[Physics]
-# Framerate of the physics system
-physics framerate = 60.0
-
 [Saves]
 
 # Name of last character played, and default for loading save files.