Geografic-Information-System/gui/wxpython/docs/wxGUI.nviz.html

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<h2>DESCRIPTION</h2>

Note: <b>wxNviz is currently under development. Not
all planned functionality is already implemented.</b>

<p>
<b>wxNviz</b> is a <em><a href="wxGUI.html">wxGUI</a></em> <b>3D view
mode</b> which allows users to realistically render multiple
<em>surfaces</em> (2D raster maps) in a 3D space, optionally using
thematic coloring, draping 2D <em>vector</em> data or different 2D raster data
over the surfaces, displaying 3D vector data in the space, and visualization
of <em>3D rasters</em>.

<p>
To start the wxGUI 3D view mode, choose '3D view' from the map
toolbar. You can switch between 2D and 3D view. The region in 
3D view is updated according to displayed region in 2D view.
<p>
wxNviz is emphasized on the ease and speed of viewer positioning and
provided flexibility for using a wide range of data. A low resolution
surface or wire grid (optional) provides real-time viewer positioning
capabilities. Coarse and fine resolution controls allow the user to
further refine drawing speed and detail as needed. Continuous scaling
of elevation provides the ability to use various data types for the
vertical dimension.

<p>
For each session of wxNviz, you might want the same set of 2D/3D
raster and vector data, view parameters, or other attributes. For
consistency between sessions, you can store this information in the
GRASS <em>workspace</em> file (gxw). Workspace contains information to
restore "state" of the system in 2D and if wxNviz is enabled also in
the 3D display mode.

<h2>3D View Toolbar</h2>

<center>
<br><img src="wxGUI_nviz_toolbar.jpg" border="1" alt="toolbar"><br><br>
</center>

<dl>
  <dt><img src="icons/script-save.png" alt="icon">&nbsp;
    <em>Generate command for m.nviz.image</em></dt>
  <dd>Generate command for m.nviz.image based on current state.</dd>
  <dt><img src="icons/settings.png" alt="icon">&nbsp;
    <em>Show 3D view mode settings</em></dt>
  <dd>Show dialog with settings for wxGUI 3D view mode. The user
  settings can be stored in wxGUI settings file.</dd>
  <dt><img src="icons/help.png" alt="icon">&nbsp;
    <em>Show help</em></dt>
  <dd>Show this help.</dd>
</dl>

<h2>3D View Layer Manager Toolbox</h2>

The 3D view toolbox is integrated in the Layer Manager. The toolbox
has several tabs:

<ul>
  <li><b>View</b> for view controlling,</li>
  <li><b>Data</b> for data properties,</li>
  <li><b>Appearance</b> for appearance settings (lighting, fringes, ...).</li>
  <li><b>Analysis</b> for various data analyses (only cutting planes so far).</li>
  <li><b>Animation</b> for creating simple animations.</li>
</ul>

<h3>View</h3>

You can use this panel to set the <em>position, direction, and
perspective</em> of the view. The position box shows a puck with a
direction line pointing to the center. The direction line indicates
the look direction (azimuth). You click and drag the puck to change
the current eye position. Another way to change eye position is
to press the buttons around the position box representing cardinal
and ordinal directions. 
  
<p>
There are four other buttons for view control in the bottom of this panel
(following label <em>Look:</em>):
<ul>
  <li><em>here</em> requires you to click on Map Display Window to determine
   the point to look at.</li>
   <li><em>center</em> changes the point you are looking at to the center.</li>
   <li><em>top</em> moves the current eye position above the map center.</li>
   <li><em>reset</em> returns all current view settings to their default values.</li>
</ul>

<center>
  <br><img src="wxGUI_nviz_tools_view.jpg" border="1" alt="toolbox"><br><br>
</center>

You can adjust the viewer's height above the scene, perspective and
twist value to rotate the scene about the horizontal axis. An angle of
0 is flat. The scene rotates between -90 and 90 degrees.

<p>
You can also adjusts the vertical exaggeration of the surface. As an
example, if the easting and northing are in meters and the elevation
in feet, a vertical exaggeration of 0.305 would produce a true
(unexaggerated) surface.
<p>
View parameters can be controlled by sliders or edited directly in the
text boxes. It is possible to enter values which are out of slider's range
(and it will then adjust to the new range).

<h4>Fly-through mode</h4>

View can be changed in fly-through mode (can be activated in Map Display
toolbar), which enables to change the view smoothly and therefore it is
suitable for creating animation (see below). To start flying, press left
mouse button and hold it down to continue flying. Flight direction is
controlled by mouse cursor position on screen. Flight speed can be
increased/decreased stepwise by keys PageUp/PageDown, Home/End or Up/Down
arrows. Speed is increased multiple times while Shift key is held down.
Holding down Ctrl key switches flight mode in the way that position of
viewpoint is changed (not the direction).

<h3>Data properties</h3> 
This tab controls the parameters related to map layers. It consists
of four collapsible panels - <em>Surface</em>, <em>Constant surface</em>, 
<em>Vector</em> and <em>3D raster</em>.

<h4>Surface</h4>

Each active raster map layer from the current layer tree is displayed as
surface in the 3D space. This panel controls how loaded surfaces are
drawn. To change parameters of a surface, it must be selected in the very
top part of the panel.
<p>
The top half of the panel has drawing style options.
Surface can be drawn as a wire mesh or using filled polygons (most
realistic). You can set draw <b>mode</b> to <em>coarse</em> (fast
display mode), <em>fine</em> (draws surface as filled polygons with
fine resolution) or <em>both</em> (which combines coarse and fine
mode). Additionally set coarse <b>style</b> to <em>wire</em> to draw
the surface as wire mesh (you can also choose color of the wire)
or <em>surface</em> to draw the surface using coarse resolution filled
polygons. This is a low resolution version of the polygon surface
style.

E.g. surface is drawn as a wire mesh if you set <b>mode</b>
to <em>coarse</em> and <b>style</b> to <em>wire</em>. Note that it
differs from the mesh drawn in fast display mode because hidden lines
are not drawn. To draw the surface using filled polygons, but with
wire mesh draped over it, choose <b>mode</b> <em>both</em>
and <b>style</b> <em>wire</em>.

Beside mode and style you can also choose style of <b>shading</b> used
for the surface. <em>Gouraud</em> style draws the surfaces with a
smooth shading to blend individual cell colors together, <em>flat</em>
draws the surfaces with flat shading with one color for every two
cells. The surface appears faceted.

<p>
To set given draw settings for all loaded surfaces press button "Set to
all".

<p>
The bottom half of the panel has options to set, unset or modify
attributes of the current surface. Separate raster data or constants can
be used for various attributes of the surface:
<ul>
  <li><b>color</b> - raster map or constant color to drape over the current
    surface. This option is useful for draping imagery such as aerial
    photography over a DEM.</li>
  <li><b>mask</b> - raster map that controls the areas displayed from
    the current surface.</li>
  <li><b>transparency</b> - raster map or constant value that controls
    the transparency of the current surface. The default is completely
    opaque. Range from 0 (opaque) to 100 (transparent).</li>
  <li><b>shininess</b> - raster map or constant value that controls
    the shininess (reflectivity) of the current surface. Range from 0 to
    100.</li>
</ul>

<p>
In the very bottom part of the panel position of surface can be set.
To move the surface right (looking from the south) choose <em>X</em> axis
and set some positive value. To reset the surface position press
<em>Reset</em> button.

<center>
  <br><img src="wxGUI_nviz_tools_surface.jpg" border="1" alt="toolbox"><br><br>
</center>

<h4>Constant surface</h4>
It is possible to add constant surface and set its properties like 
fine resolution, value (height), color and transparency. It behaves 
similarly to surface but it has less options.

<h4>Vector</h4>

2D vector data can be draped on the selected surfaces with various
markers to represent point data; you can use attribute of vector
features to determine size, color, shape of glyph.

3D vector data including volumes (closed group of faces with one
kernel inside) is also supported.
This panel controls how loaded 2D or 3D vector data are drawn.

<p>
You can define the width (in pixels) of the line features, the color
used for lines or point markers.

<p>
If vector map is 2D you can display vector features as flat at a
specified elevation or drape it over a surface(s) at a specified
height. Use the height control to set the flat elevation or the drape
height above the surface(s). In case of multiple surfaces it is possible
to specify which surfaces is the vector map draped over.

<p>
For display purposes, it is better to set the height slightly above
the surface. If the height is set at zero, portions of the vector may
disappear into the surface(s).

<p>
For 2D/3D vector points you can also set the size of the markers.
<!-- and the width (in pixels) of the line used to draw the point markers (only
applies to wire-frame markers). -->
 Currently are implemented these markers:

<ul>
  <li><b>x</b> sets the current points markers to a 2D "X",</li>
  <li><b>sphere</b> - solid 3D sphere,</li>
  <li><b>diamond</b> - solid 3D diamond,</li>
  <li><b>cube</b> - solid 3D cube,</li>
  <li><b>box</b> - hollow 3D cube,</li>
  <li><b>gyroscope</b> - hollow 3D sphere,</li>
  <li><b>asterisk</b> - 3D line-star.</li>
</ul>
 
<p>
Thematic mapping can be used to determine marker color and size
(and line color and width).

<center>
  <br><img src="wxGUI_nviz_tools_vector.jpg" border="1" alt="toolbox"><br><br>
</center>

<h4>3D rasters</h4>

3D raster maps (volumes, voxel models) can be displayed either as isosurfaces
or slices.
Similarly to surface panel you can define draw <b>shading</b> -
<em>gouraud</em> (draws the 3D rasters with a smooth shading to blend
individual cell colors together) and <em>flat</em> (draws the 3D rasters with
flat shading with one color for every two cells. The 3D raster appears
faceted). As mentioned above currently are supported two visualization
modes:

<ul>
  <li><b>isosurface</b> - the levels of values for drawing the
  3D raster(s) as isosurfaces,</li>
  <li>and <b>slice</b> -  drawing the 3D raster
  as cross-sections.</li>
</ul>
<p>
The middle part of the panel has controls to add, delete, move up/down
selected  isosurface or slice. The bottom part differs for isosurface and
slice.  When choosing an isosurface, this part the of panel has options to
set, unset or modify attributes of the current isosurface.  Various
attributes of the isosurface can be defined, similarly to surface
attributes:

<ul>
  <li><b>isosurface value</b> - reference isosurface value (height in map
  units).</li>
  <li><b>color</b> - raster map or constant color to drape over the
  current 3D raster.</li>
  <li><b>mask</b> - raster map that controls the areas displayed from
    the current 3D raster.</li>
  <li><b>transparency</b> - raster map or constant value that controls
    the transparency of the current 3D raster. The default is completely
    opaque. Range from 0 (opaque) to 100 (transparent).</li>
  <li><b>shininess</b> - raster map or constant value that controls
    the shininess (reflectivity) of the current 3D raster. Range from 0 to
    100.</li>
</ul>

In case of 3D raster slice the bottom part of the panel controls the slice 
attributes (which axis is slice parallel to, position of slice edges,
transparency). Press button <em>Reset</em> to reset slice position
attributes.
<p>
3D rasters can be moved the same way like surfaces do.

<center>
  <br><img src="wxGUI_nviz_tools_volume.jpg" border="1" alt="toolbox"><br><br>
</center>

<h3>Analysis</h3>
<em>Analysis</em> tab contains <em>Cutting planes</em> panel.

<h4>Cutting planes</h4>

Cutting planes allow cutting surfaces along a plane. You can switch 
between six planes; to disable cutting planes switch to <em>None</em>.
Initially the plane is vertical, you can change it to horizontal by
setting <em>tilt</em> 90 degrees. The <em>X</em> and <em>Y</em> values
specify the rotation center of plane. You can see better what <em>X</em>
and <em>Y</em> do when changing <em>rotation</em>.  The <em>Height</em>
parameter applies only when changing <em>tilt</em> concurrently. 
Press the <em>Reset</em> button to reset the current cutting plane.
<p>
In case of multiple surfaces you can visualize the cutting plane by
<em>Shading</em>. Shading is visible only when more than one surface
is loaded and these surfaces must have the same fine resolution set.


<h3>Appearance</h3>
Appearance tab consists of three collapsible panels:

<ul>
  <li><em>Lighting</em> for adjusting light source</li>
  <li><em>Fringe</em> for drawing fringes
  <li><em>Decorations</em> to display north arrow and scale bar</li>
</ul>
<p>
The <em>lighting</em> panel enables to change the position of light
source, light color, brightness and ambient. Light position is controlled 
similarly to eye position. If option <em>Show light model</em> is enabled
light model is displayed to visualize the light settings.

<center>
  <br><img src="wxGUI_nviz_tools_light.jpg" border="1" alt="toolbox"><br><br>
</center>
<p>
The <em>Fringe</em> panel allows you to draw fringes in different
directions (North &amp; East, South &amp; East, South &amp; West, North
&amp; West). It is possible to set the fringe color and height of the
bottom edge.
<p>
The <em>Decorations</em> panel enables to display north arrow and simple
scale bar. North arrow and scale bar length is determined in map units. 
You can display more than one scale bar.

<h3>Animation</h3>
Animation panel enables to create a simple animation as a sequence of
images. Press 'Record' button and start changing the view. Views are
recorded in given interval (FPS - Frames Per Second). After recording, the
animation can be replayed. To save the animation, fill in the directory
and file prefix, choose image format (PPM or TIF) and then press 'Save'.
Now wait until the last image is generated.

It is recommended to record animations using fly-through mode to achieve
smooth motion.

<h2>Settings</h2>

This panel has controls which allows user to set default surface,
vector and 3D raster data attributes. You can also modify default view
parameters, or to set the background color of the Map Display Window
(the default color is white).


<h2>To be implemented</h2>

<ul>
  <li>Labels, decoration, etc. (Implemented, but not fully functional)</li>
  <li>Surface - mask by zero/elevation, more interactive positioning</li>
  <li>Vector points - implement display mode flat/surface for 2D points</li>
  <li>...</li>
</ul>


<h2>NOTE</h2>
wxNviz is under active development and
distributed as &quot;Experimental Prototype&quot;.

<p>
Please note that with wxGTK port of wxPython (Linux systems), a problem
might appear during wxNviz initialization (nothing is rendered at all) or
when rendering vectors (bad order of rendering surfaces and vectors). If
you encounter such problems, try to change a depth buffer number in
<i>wxGUI Settings &gt; Preferences &gt; Map Display  &gt; Advanced</i>
(possible numbers are 0, 16, 24, 32). It is currently not possible to
automatically determine the right number which is working for your
computer.


<h2>SEE ALSO</h2>

<em>
  <a href="wxGUI.html">wxGUI</a><br>
  <a href="wxGUI.components.html">wxGUI components</a>
</em>

<p>
See also <a href="http://grasswiki.osgeo.org/wiki/WxNVIZ">wiki</a> page
(especially various <a href="http://grasswiki.osgeo.org/wiki/WxNVIZ#Video_tutorials">video
tutorials</a>).

<br><br>

Command-line module <em><a href="m.nviz.image.html">m.nviz.image</a></em>.
<br><br>


<h2>AUTHORS</h2>

<b>The wxNviz GUI</b>
<p>
<a href="http://geo.fsv.cvut.cz/gwiki/Landa">Martin
Landa</a>, <a href="http://grasswiki.osgeo.org/wiki/WxNviz_GSoC_2008">Google
Summer of Code 2008</a> (mentor: Michael Barton)
and <a href="http://grasswiki.osgeo.org/wiki/WxNviz_GSoC_2010">2010</a> (mentor: Helena Mitasova)<br>
Anna Kratochvilova, <a href="http://grasswiki.osgeo.org/wiki/WxNviz_GSoC_2011">Google
Summer of Code 2011</a> (mentor: Martin Landa)

<p>
<b>The OGSF library and NVIZ engine</b>
<p>

NVIZ (GRASS's <i>n</i>-dimensional visualization suite) was written
by Bill Brown, Terry Baker, Mark Astley, and David Gerdes,
U.S. Army Corps of Engineers Research Laboratories, Champaign,
Illinois and UI GMS Laboratory, Urbana, IL in the early 1990s.
<p>
Original documentation was written by Terry Baker (spring 1995), and
updated by Mark Astley, based on a document written by Bill Brown. 
Additional design help and funding in the early 1990s by Helena
Mitasova (CERL). Tcl/Tk support added by Terry Baker. Ported to Linux
by Jaro Hofierka and others. Conversion from SGI IRIS GL code to
OpenGL by Justin Hickey. Further program and documentation (2004)
updates by Bob Covill, Tekmap Consulting. 3D volume support by Tomas
Paudits with supervision from Jaro Hofierka and Helena Mitasova.
Fly-through mode, thematic site attributes, and picking by Massimo
Cuomo (ACS) with updates by Michael Barton. GRASS 6 vector support by
Radim Blazek. Additional updates by Markus Neteler, Martin Landa, 
Glynn Clements, and Hamish Bowman.

<p>
NVIZ evolved from the earlier GRASS program <em>SG3d</em> written
for Silicon Graphics IRIS GL by Bill Brown and Dave Gerdes at USA
CERL, 1990-1995 and from the NVIZ Motif version written by Bill Brown
with contributions by Terrance McGhee.


<p>
<i>$Date$</i>