From Laurens Voerman, "While reading the code for setUpViewFor3DSphericalDisplay I noticed that the top face of the cube map uses Draw/Read buffer GL_BACK, while all other faces are using the GL_FRONT buffer. This because the buffer variable is hidden by a new buffer at lower scope.

Removing the local variable tested (win32 and linux64) and works fine."

src/osgViewer/View.cpp

@@ -938,7 +938,6 @@ void View::setUpViewFor3DSphericalDisplay(double radius, double collar, unsigned
         camera->setName("Top face camera");
         camera->setGraphicsContext(gc.get());
         camera->setViewport(new osg::Viewport(0,0,camera_width, camera_height));
-        GLenum buffer = traits->doubleBuffer ? GL_BACK : GL_FRONT;
         camera->setDrawBuffer(buffer);
         camera->setReadBuffer(buffer);
         camera->setAllowEventFocus(false);