You're probably going to want to run/build all the qt demos by opening the .pro files for the specific examples.
chown -R yourusername /opt/qt5/examples/
When I went to build the opengl/textures example by opening the textures.pro file within qtcreator, it automatically configured the project BUT it was pointing to QT4 by default.
I got a strange error that said it could not find QtWidgets when I was trying to build using qt4. With Qt5 as the build tool, the problem went away.
MAKE SURE YOU POINT TO QT5 as the project build for debug/release because it's not the default in qtcreator. Otherwise you will get strange errors when building. This problem is easy to spot in the compilation output which should be showing qt5 include and qt5 libs paths.
2:58:51: Running steps for project textures...
12:58:51: Starting: "/usr/bin/make" clean -w
make: Entering directory `/opt/qt5/examples/qtbase/opengl/textures-build-Desktop Release'
rm -f qrc_textures.cpp
rm -f moc_glwidget.cpp moc_window.cpp
rm -f glwidget.o main.o window.o qrc_textures.o moc_glwidget.o moc_window.o
rm -f *~ core *.core
make: Leaving directory `/opt/qt5/examples/qtbase/opengl/textures-build-Desktop-Release'
12:58:52: The process "/usr/bin/make" exited normally.
12:58:52: Configuration unchanged, skipping qmake step.
12:58:52: Starting: "/usr/bin/make" -w
make: Entering directory `/opt/qt5/examples/qtbase/opengl/textures-build-Desktop-Release'
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -fPIE -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. -o glwidget.o ../textures/glwidget.cpp
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -fPIE -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. -o main.o ../textures/main.cpp
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -fPIE -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. -o window.o ../textures/window.cpp
/opt/qt5/bin/rcc -name textures ../textures/textures.qrc -o qrc_textures.cpp
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -fPIE -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. -o qrc_textures.o qrc_textures.cpp
/opt/qt5/bin/moc -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. ../textures/glwidget.h -o moc_glwidget.cpp
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -fPIE -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. -o moc_glwidget.o moc_glwidget.cpp
/opt/qt5/bin/moc -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. ../textures/window.h -o moc_window.cpp
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -fPIE -DQT_NO_DEBUG -DQT_OPENGL_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../../../../mkspecs/linux-g++-64 -I../textures -I../../../../include -I../../../../include/QtOpenGL -I../../../../include/QtWidgets -I../../../../include/QtGui -I../../../../include/QtCore -I. -I. -o moc_window.o moc_window.cpp
g++ -m64 -Wl,-O1 -Wl,-rpath,/opt/qt5/lib -o textures glwidget.o main.o window.o qrc_textures.o moc_glwidget.o moc_window.o -L/usr/X11R6/lib64 -L/opt/qt5/lib -lQtOpenGL -lQtWidgets -lQtGui -lQtCore -lGL -lpthread
make: Leaving directory `/opt/qt5/examples/qtbase/opengl/textures-build-Desktop-Release'
12:58:57: The process "/usr/bin/make" exited normally.
echo 'export PATH=/opt/qt5/bin:$PATH' >> ~/.bashrc
qmlscene
from the command line, as described in the tutorial? If so, what's the exact output on the command line?