From 2fe86f2b85aa9a29f8a0d80b8982c97afc643b57 Mon Sep 17 00:00:00 2001
From: scrawl <scrawl@baseoftrash.de>
Date: Tue, 27 May 2014 17:39:04 +0200
Subject: [PATCH] Consider hit normal for item drop test (Fixes #995)

---
 apps/openmw/mwworld/physicssystem.cpp |  4 ++--
 apps/openmw/mwworld/physicssystem.hpp |  5 +++--
 apps/openmw/mwworld/worldimp.cpp      | 13 ++++++++-----
 libs/openengine/bullet/physic.cpp     |  8 ++++++--
 libs/openengine/bullet/physic.hpp     |  4 +++-
 5 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/apps/openmw/mwworld/physicssystem.cpp b/apps/openmw/mwworld/physicssystem.cpp
index b8f0f8699..e93d9e640 100644
--- a/apps/openmw/mwworld/physicssystem.cpp
+++ b/apps/openmw/mwworld/physicssystem.cpp
@@ -492,7 +492,7 @@ namespace MWWorld
         return std::make_pair(true, ray.getPoint(len * test.second));
     }
 
-    std::pair<bool, Ogre::Vector3> PhysicsSystem::castRay(float mouseX, float mouseY)
+    std::pair<bool, Ogre::Vector3> PhysicsSystem::castRay(float mouseX, float mouseY, Ogre::Vector3* normal)
     {
         Ogre::Ray ray = mRender.getCamera()->getCameraToViewportRay(
             mouseX,
@@ -504,7 +504,7 @@ namespace MWWorld
         _from = btVector3(from.x, from.y, from.z);
         _to = btVector3(to.x, to.y, to.z);
 
-        std::pair<std::string, float> result = mEngine->rayTest(_from, _to);
+        std::pair<std::string, float> result = mEngine->rayTest(_from, _to, true, false, normal);
 
         if (result.first == "")
             return std::make_pair(false, Ogre::Vector3());
diff --git a/apps/openmw/mwworld/physicssystem.hpp b/apps/openmw/mwworld/physicssystem.hpp
index 3dcd088f5..899d7144d 100644
--- a/apps/openmw/mwworld/physicssystem.hpp
+++ b/apps/openmw/mwworld/physicssystem.hpp
@@ -70,8 +70,9 @@ namespace MWWorld
             std::pair<bool, Ogre::Vector3>
             castRay(const Ogre::Vector3 &orig, const Ogre::Vector3 &dir, float len);
 
-            std::pair<bool, Ogre::Vector3> castRay(float mouseX, float mouseY);
-            ///< cast ray from the mouse, return true if it hit something and the first result (in OGRE coordinates)
+            std::pair<bool, Ogre::Vector3> castRay(float mouseX, float mouseY, Ogre::Vector3* normal = NULL);
+            ///< cast ray from the mouse, return true if it hit something and the first result
+            /// @param normal if non-NULL, the hit normal will be written there (if there is a hit)
 
             OEngine::Physic::PhysicEngine* getEngine();
 
diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index 435ca8b36..fdc203182 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -1620,13 +1620,16 @@ namespace MWWorld
 
     bool World::canPlaceObject(float cursorX, float cursorY)
     {
-        std::pair<bool, Ogre::Vector3> result = mPhysics->castRay(cursorX, cursorY);
+        Ogre::Vector3 normal(0,0,0);
+        std::pair<bool, Ogre::Vector3> result = mPhysics->castRay(cursorX, cursorY, &normal);
 
-        /// \todo also check if the wanted position is on a flat surface, and not e.g. against a vertical wall!
-
-        if (!result.first)
+        if (result.first)
+        {
+            // check if the wanted position is on a flat surface, and not e.g. against a vertical wall
+            return (normal.angleBetween(Ogre::Vector3(0.f,0.f,1.f)).valueDegrees() < 30);
+        }
+        else
             return false;
-        return true;
     }
 
 
diff --git a/libs/openengine/bullet/physic.cpp b/libs/openengine/bullet/physic.cpp
index 6646ce273..235300b43 100644
--- a/libs/openengine/bullet/physic.cpp
+++ b/libs/openengine/bullet/physic.cpp
@@ -677,7 +677,7 @@ namespace Physic
     {
     }
 
-    std::pair<std::string,float> PhysicEngine::rayTest(btVector3& from,btVector3& to,bool raycastingObjectOnly,bool ignoreHeightMap)
+    std::pair<std::string,float> PhysicEngine::rayTest(btVector3& from,btVector3& to,bool raycastingObjectOnly,bool ignoreHeightMap, Ogre::Vector3* normal)
     {
         std::string name = "";
         float d = -1;
@@ -694,7 +694,11 @@ namespace Physic
         if (resultCallback1.hasHit())
         {
             name = static_cast<const RigidBody&>(*resultCallback1.m_collisionObject).mName;
-            d = resultCallback1.m_closestHitFraction;;
+            d = resultCallback1.m_closestHitFraction;
+            if (normal)
+                *normal = Ogre::Vector3(resultCallback1.m_hitNormalWorld.x(),
+                                        resultCallback1.m_hitNormalWorld.y(),
+                                        resultCallback1.m_hitNormalWorld.z());
         }
 
         return std::pair<std::string,float>(name,d);
diff --git a/libs/openengine/bullet/physic.hpp b/libs/openengine/bullet/physic.hpp
index 16eb45306..803986d5b 100644
--- a/libs/openengine/bullet/physic.hpp
+++ b/libs/openengine/bullet/physic.hpp
@@ -308,8 +308,10 @@ namespace Physic
 
         /**
          * Return the closest object hit by a ray. If there are no objects, it will return ("",-1).
+         * If \a normal is non-NULL, the hit normal will be written there (if there is a hit)
          */
-        std::pair<std::string,float> rayTest(btVector3& from,btVector3& to,bool raycastingObjectOnly = true,bool ignoreHeightMap = false);
+        std::pair<std::string,float> rayTest(btVector3& from,btVector3& to,bool raycastingObjectOnly = true,
+                                             bool ignoreHeightMap = false, Ogre::Vector3* normal = NULL);
 
         /**
          * Return all objects hit by a ray.