From ed817b0e0532b4baea698dbb68934672f8eb83b6 Mon Sep 17 00:00:00 2001
From: wmayer <wmayer@users.sourceforge.net>
Date: Mon, 13 Nov 2017 21:53:10 +0100
Subject: [PATCH] make retrieving view direction numerically more stable,
 change orientation of bottom view

---
 src/Gui/View3DInventor.cpp       | 2 +-
 src/Gui/View3DInventorViewer.cpp | 6 ++----
 src/Gui/View3DPy.cpp             | 2 +-
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/src/Gui/View3DInventor.cpp b/src/Gui/View3DInventor.cpp
index 76becbb088..1616723c4e 100644
--- a/src/Gui/View3DInventor.cpp
+++ b/src/Gui/View3DInventor.cpp
@@ -664,7 +664,7 @@ bool View3DInventor::onMsg(const char* pMsg, const char** ppReturn)
         return true;
     }
     else if(strcmp("ViewBottom",pMsg) == 0 ) {
-        _viewer->setCameraOrientation(SbRotation(-1, 0, 0, 0));
+        _viewer->setCameraOrientation(SbRotation(0, -1, 0, 0));
         _viewer->viewAll();
         return true;
     }
diff --git a/src/Gui/View3DInventorViewer.cpp b/src/Gui/View3DInventorViewer.cpp
index 31d5101f3a..d756f152db 100644
--- a/src/Gui/View3DInventorViewer.cpp
+++ b/src/Gui/View3DInventorViewer.cpp
@@ -1766,10 +1766,8 @@ SbVec3f View3DInventorViewer::getViewDirection() const
 
     if (!cam) return SbVec3f(0,0,-1);  // this is the default
 
-    SbRotation camrot = cam->orientation.getValue();
-    SbVec3f lookat(0, 0, -1); // init to default view direction vector
-    camrot.multVec(lookat, lookat);
-    return lookat;
+    SbVec3f projDir = cam->getViewVolume().getProjectionDirection();
+    return projDir;
 }
 
 void View3DInventorViewer::setViewDirection(SbVec3f dir)
diff --git a/src/Gui/View3DPy.cpp b/src/Gui/View3DPy.cpp
index d359d9293a..15761214ff 100644
--- a/src/Gui/View3DPy.cpp
+++ b/src/Gui/View3DPy.cpp
@@ -325,7 +325,7 @@ Py::Object View3DInventorPy::viewBottom(const Py::Tuple& args)
         throw Py::Exception();
 
     try {
-        _view->getViewer()->setCameraOrientation(SbRotation(-1, 0, 0, 0));
+        _view->getViewer()->setCameraOrientation(SbRotation(0, -1, 0, 0));
     }
     catch (const Base::Exception& e) {
         throw Py::Exception(e.what());