Documentation for textured surface example

Change-Id: I517b02a31e342dc3ae2c1c80805f811f9d9670ff
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@digia.com>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@digia.com>

1 files changed, 81 insertions, 2 deletions

diff --git a/examples/datavisualization/texturesurface/doc/src/texturesurface.qdoc b/examples/datavisualization/texturesurface/doc/src/texturesurface.qdoc
index ee93dd0a..a4aa219e 100644
--- a/examples/datavisualization/texturesurface/doc/src/texturesurface.qdoc
+++ b/examples/datavisualization/texturesurface/doc/src/texturesurface.qdoc
@@ -18,9 +18,88 @@
 
 /*!
     \example texturesurface
-    \title Texture Surface Example
+    \title Textured Surface Example
     \ingroup qtdatavisualization_examples
     \brief Using texture with Q3DSurface.
 
-	TODO
+    The textured surface example shows how to add an image as a texture for a surface. The example
+    shows also how to:
+
+    \list
+        \li Create a surface series from an image
+        \li Highlight an area of the surface
+        \li Use custom input handler to enable zooming and panning
+    \endlist
+
+    \image texturesurface-example.png
+
+    \section1 Texture to a surface series
+
+    The image to be set as a texture to a surface can be set using QSurface3DSeries::setTextureFile().
+    In this example we have added a check box to control if the texture is set or not. The
+    following code extract is for reacting to the check box selections. The image in this
+    example is read from the resource file where it is as a JPG file. Setting an empty file
+    with the method clears the texture, and the surface uses the gradients or colors from the theme.
+
+    \snippet texturesurface/surfacegraph.cpp 0
+
+    \section1 Topographic surface series
+
+    The topographic data for this example is obtained from National Land Survey of Finland. It
+    provides a product called \c{Elevation Model 2 m}, which was suitable for our needs. We selected
+    Levi fell to be shown. The accuracy of the data was well beyond our needs and therefore it
+    is compressed and encoded into a PNG file. The height value from the original ASCII data is
+    encoded into RGB format using a multiplier, which you will see later on a code extract.
+    The multiplier is calculated simply by dividing the largest 24 bit value with the highest point
+    in Finland.
+
+    Qt Data Visualization has a special proxy for height map image files, but it converts
+    only one byte values. So to utilize the bigger accuracy on the data from National Land
+    Survey of Finland, we read the data from the PNG file and decode it into QSurface3DSeries.
+    The following code samples show how this is done.
+
+    First the encoding multiplier.
+    \snippet texturesurface/topographicseries.cpp 0
+
+    And then the actual decoding.
+    \snippet texturesurface/topographicseries.cpp 1
+
+    \section1 Highlight an area of the surface
+
+    The main idea on creating a highlight on the surface is to create a copy of the series and add
+    a bit of offset to the y value. On this example the class \c HighlightSeries implements the
+    creation of the copy on its \c handlePositionChange method. Firstly the \c HighlightSeries
+    needs to get the pointer to the original series and then it starts to listen the
+    QSurface3DSeries::selectedPointChanged signal.
+
+    \snippet texturesurface/highlightseries.cpp 0
+
+    When the signal arrives, first thing is to check that the position is valid. Then the ranges
+    for the  copied area are calculated and checked that they stay within the bounds. Finally
+    we simply fill the data array of the highlight series with the range from the data array of
+    topography series.
+
+    \snippet texturesurface/highlightseries.cpp 1
+
+    \section1 Use custom input handler to enable zooming and panning
+
+    For the panning the implementation is similar to the \l{Axis Range Dragging With Labels Example}.
+    The difference is that in this example we follow only dragging of X and Z axis and we don't
+    allow dragging the surface outside the graph. The control for this is very simple and done as
+    on the following example for the X axis.
+
+    \snippet texturesurface/custominputhandler.cpp 0
+
+    For the zooming we catch the \c wheelEvent and adjust the X and Y axis ranges according to delta
+    value on QWheelEvent. The Y axis is also adjusted so that the aspect ratio between Y axis and
+    XZ plane stays the same, and we don't get silly looking graph with height exaggerated too much.
+
+    \snippet texturesurface/custominputhandler.cpp 1
+
+    In this case we want to control the zoom level so that it won't get too near to or far from the
+    surface. For instance, if the value for the X axis gets below the allowed, i.e. zooming gets too
+    far, the value is set to the minimum allowed value. If the range is going to below the range
+    minimum, both ends of the axis are adjusted so that the range stays at the limit.
+
+    \snippet texturesurface/custominputhandler.cpp 2
 */