## NAME

wxGUI.Nviz

## DESCRIPTION

Note: wxGUI 3D view mode is currently under development. It's provided as an experimental prototype.

wxNviz is a wxGUI 3D view mode which allows users to realistically render multiple surfaces (raster data) in a 3D space, optionally using thematic coloring, draping 2D vector data over the surfaces, displaying 3D vector data in the space, and visualization of volume data (3D raster data).

To start the wxGUI 3D view mode, choose '3D view' from the map toolbar.

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.

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 workspace file (gxw). Workspace contains information to restore "state" of the system in 2D and if wxNviz is enabled also in the 3D display mode.

## 3D View Toolbar

Switch to view page
  Switch 3D Layer Manager Toolbox's page to the view control page.
Switch to surface page
  Switch 3D Layer Manager Toolbox's page to the surface control page (data properties).
Switch to vector page
  Switch 3D Layer Manager Toolbox's page to the vector control page (data properties).
Switch to volume page
  Switch 3D Layer Manager Toolbox's page to the volume control page (data properties).
Switch to light page
  Switch 3D Layer Manager Toolbox's page to the light control page (appearance).
Switch to fringe page
  Switch 3D Layer Manager Toolbox's page to the fringe control page (appearance).
Show 3D view mode settings
  Show dialog with settings for wxGUI 3D view mode. The user settings can be stored in wxGUI settings file.
Show help
  Show this help.
Quit
  Quit 3D view mode and switch map display to the 2D view mode.

## 3D View Layer Manager Toolbox

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

- View for view controling,
- Data for data properties,
- Appearance for appearance settings (lighting, fringes, ...).

### View

You can use this panel to set the position, direction, and perspective 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 Look at choice control.
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.

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.

Reset returns all current settings to their default values.

### Data properties - Surface

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:

- topography - raster map or constant values used as elevation (z values) for the current surface.
- color - 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.
- mask - raster map that controls the areas displayed from the current surface.
- transparency - 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).
- shininess - raster map or constant value that controls the shininess (reflectivity) of the current surface. Range from 0 to 255.
- emission - raster map or constant value that controls the light emitted from the current surface. Range from 0 to 255.

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.
Surface can be drawn as a wire mesh or using filled polygons (most realistic). You can set draw mode to coarse (fast display mode), fine (draws surface as filled polygons with fine resolution) or both (which combines coarse and fine mode). Additionally set coarse style to wire to draw the surface as wire mesh (you can also choose color of the wire) or surface 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 mode to coarse and style to wire. 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 mode both and style wire. Beside mode and style you can also choose style of shading used for the surface. Gouraud style draws the surfaces with a smooth shading to blend individual cell colors together, flat draws the surfaces with flat shading with one color for every two cells. The surface appears faceted.

To set given draw settings for all loaded surfaces press button "All".

### Data properties - Vector

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.

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

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).

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).

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:

- x sets the current points markers to a 2D "X",
- sphere - solid 3D sphere,
- diamond - solid 3D diamond,
- cube - solid 3D cube,
- box - hollow 3D cube,
- gyroscope - hollow 3D sphere,
- asterisk - 3D line-star.

### Data properties - Volume

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

- level - reference isosurface level (height in map units).
- color - raster map or constant color to drape over the current volume.
- mask - raster map that controls the areas displayed from the current volume.
- transparency - 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).
- shininess - raster map or constant value that controls the shininess (reflectivity) of the current volume. Range from 0 to 255.
- emission - raster map or constant value that controls the light emitted from the current volume. Range from 0 to 255.

This panel controls how loaded volumes are drawn. Volume can be drawn in two different modes: isosurface or slice. 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.

Similarly to surface panel you can define draw shading - gouraud (draws the volumes with a smooth shading to blend individual cell colors together) and flat (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:

- isosurface - the levels of values for drawing the volume(s) as isosurfaces,
- and slice - the levels of values for drawing the volume as cross-sections.

## Settings

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).

## To be implement

- Improve intuitive navigation (mouse, fly mode)
- Animation capabilities
- Arbitrary cutting planes
- Labels, decoration, etc.
- Scripting capabilities
- Better workspace support (view settings, lighting)
- Surface - mask by zero/elevation, more interactive positioning
- Vector points - implement display mode flat/surface for 2D points
- Volume - slice draw mode
- ...

Please note that wxNviz is under active development and distributed as "Experimental Prototype".

## SEE ALSO

wxGUI

Other wxGUI components:
Vector Digitizer
Attribute Table Manager
Graphical Modeler
Manage Ground Control Points
Cartographic Composer

See also wiki page.
Command-line module m.nviz.image.
Original TCL/TK-based Nviz.

## AUTHORS

Martin Landa, Google Summer of Code 2008 (mentor: Michael Barton) and Google Summer of Code 2010 (mentor: Helena Mitasova)

$Date: 2011-10-14 19:44:26 +0200 (Fri, 14 Oct 2011) $

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