X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FMain%2Fviewer.cxx;h=57e60f48110007c8eff18f06cd0f8fc05f2271b9;hb=38226af24ec01e8f0a20d7fd73ef838a69f6ef25;hp=05816f8bc6c407434dfef501a1b519dbf835d854;hpb=f2a817d1370cde5a94474344a65bacb2f7845352;p=flightgear.git

diff --git a/src/Main/viewer.cxx b/src/Main/viewer.cxx
index 05816f8bc..57e60f481 100644
--- a/src/Main/viewer.cxx
+++ b/src/Main/viewer.cxx
@@ -289,7 +289,14 @@ void
 FGViewer::setHeadingOffset_deg (double heading_offset_deg)
 {
   _dirty = true;
-  _heading_offset_deg = heading_offset_deg;
+  if (_at_model && (_offset_m.x() == 0.0)&&(_offset_m.z() == 0.0))
+  {
+      /* avoid optical effects (e.g. rotating sky) when "looking at" with
+       * heading offsets x==z==0 (view heading cannot change). */
+      _heading_offset_deg = 0.0;
+  }
+  else
+      _heading_offset_deg = heading_offset_deg;
 }
 
 void
@@ -317,6 +324,14 @@ void
 FGViewer::setGoalHeadingOffset_deg (double goal_heading_offset_deg)
 {
   _dirty = true;
+  if (_at_model && (_offset_m.x() == 0.0)&&(_offset_m.z() == 0.0))
+  {
+      /* avoid optical effects (e.g. rotating sky) when "looking at" with
+       * heading offsets x==z==0 (view heading cannot change). */
+      _goal_heading_offset_deg = 0.0;
+      return;
+  }
+  
   _goal_heading_offset_deg = goal_heading_offset_deg;
   while ( _goal_heading_offset_deg < 0.0 ) {
     _goal_heading_offset_deg += 360;