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

<h2>DESCRIPTION</h2>

<b>Note:</b> <em>wxGUI Nviz extension is currently under development. Not
all functionality is implemented.</em>

<p>
<b>wxGUI Nviz extension</b> allows users to realistically render multiple
<em>surfaces</em> (raster data) in a 3D space, optionally using
thematic coloring, draping 2D <em>vector</em> data over the surfaces,
displaying 3D vector data in the space, and visualization
of <em>volume</em> data (3D raster data).

<p>
To start the wxGUI Nviz extension, choose '3D view' from the map toolbar.
<p>
Nviz 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 Nviz, 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 <em>workspace</em> file (gxw). Workspace file contains information
to restore "state" of the system in 2D and if Nviz is enabled also in
the 3D display mode.

<h2>Data visualization</h2>

<h3>Surfaces</h3>

Each active raster map layer from the current layer tree is displayed
as surface in the 3D space. Separate raster data or constants can be
used for various attributes of the surface:

<ul>
  <li><b>topography</b> - raster map or constant values used as elevation (z
    values) for the current surface.</li>
  <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 255 (transparent).</li>
  <li><b>shininess</b> - raster map or constant value that controls
    the shininess (reflectivity) of the current surface. Range from 0 to
    255.</li>
  <li><b>emission</b> - raster map or constant value that controls the
    light emitted from the current surface. Range from 0 to 255.</li>
</ul>

<h3>Vector data</h3>

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.

<h3>Volumes</h3>

Volumes can be displayed either as isosurfaces or slices. Various
attributes of the isosurface can be defined, similarly to surface
attributes:

<ul>
  <li><b>level</b> - reference isosurface level (height in map
  units).</li>
  <li><b>color</b> - raster map or constant color to drape over the
  current volume.</li>
  <li><b>mask</b> - raster map that controls the areas displayed from
    the current volume.</li>
  <li><b>transparency</b> - raster map or constant value that controls
    the transparency of the current volume. The default is completely
    opaque. Range from 0 (opaque) to 255 (transparent).</li>
  <li><b>shininess</b> - raster map or constant value that controls
    the shininess (reflectivity) of the current volume. Range from 0 to
    255.</li>
  <li><b>emission</b> - raster map or constant value that controls the
    light emitted from the current volume. Range from 0 to 255.</li>
</ul>

<h2>Nviz Toolbox Window</h2>

The toolbox window has currently three tabs:

<ul>
  <li>View<li>
  <li>Layer properties<li>
  <li>Settings</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. The box annotations are North, South,
East, and West. You can also set exact position using <em>Look
  at</em> choice control.

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

You can adjust the viewer's height above the scene, angle of view or
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>
  <em>Reset</em> returns all current settings to their default values.

<h3>Surface properties</h3>

This panel controls how loaded surfaces are drawn. The top half of the
panel has options to set, unset or modify attributes of the current
surface.The bottom half has drawing style options, masking or changing
surface position in the space.

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

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
  "All".

<h3>Vector properties</h3>

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.

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

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).

<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>
 
<h3>Volume properties</h3>

This panel controls how loaded volumes are drawn. Volume can be drawn
in two different modes: <b>isosurface</b> or <b>slice</b>. The top
part of the panel has drawing style options. The middle part has
controls to add, delete, move up/down selected isosurface or
slices. The bottom part has options to set, unset or modify attributes
of the current isosurface or slice.

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

Similarly to surface panel you can define draw <b>shading</b>
- <em>gouraud</em> (draws the volumes with a smooth shading to blend
individual cell colors together) and <em>flat</em> (draws the volumes
with flat shading with one color for every two cells. The volume
appears faceted). As mentioned above currently are supported two
visualization modes:

<ul>
  <li><b>isosurface</b> - the levels of values for drawing the
  volume(s) as isosurfaces;</li>
  <li>and <b>slice</b> - the levels of values for drawing the volume
  as cross-sections.</li>
</ul>

<h2>Settings</h2>

This panel has controls which allows user to set default surface,
vector and volume 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 implement</h2>

<ul>
  <li>Improve intuitive navigation (mouse, fly mode)</li>
  <li>Interactive lighting controls</li>
  <li>Animation capabilities</li>
  <li>Data querying and measuring</li>
  <li>Arbitrary cutting planes</li>
  <li>Labels, decoration, etc.</li>
  <li>Scripting capabilities</li>
  <li>Better workspace support (view settings, lighting)
  <li>Image Dump</li>
  <li>Surface - mask by zero/elevation, more interactive positioning</li>
  <li>Vector points - implement display mode flat/surface for 2D points</li>
  <li>Volume - slice draw mode</li>
  <li>...</li>
</ul>

<p>
<b>Please note that the wxGUI Nviz extension is under active development and
distributed as &quot;Experimental Prototype&quot;.</b>

<h2>SEE ALSO</h2>

See also <a href="http://grass.osgeo.org/wiki/WxNVIZ">wiki</a> page.
<br><br>

Command-line module <em><a href="nviz_cmd.html">nviz_cmd</a></em>.
<br><br>

Original <a href="nviz.html">TCL/TK-based</a> Nviz.

<h2>AUTHORS</h2>

Martin Landa, Google Summer of Code 2008 (Mentor: Michael Barton)

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