ecmview 0.7.0

ecmview

This manual was last updated 12 November 2012 for version 0.7.0 of ecmview.

Copyright © 2012 Computer Graphics Group, University of Siegen, Germany. Written by Martin Lambers (martin.lambers@uni-siegen.de). See http://www.cg.informatik.uni-siegen.de/ for contact information.

Copying and distribution of this file and the accompanying media files, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved. These files are offered as-is, without any warranty.

Short Contents:

• Introduction
• Accessing ECM Databases
• Navigating
• Processing and Combining Databases
• Lighting
• Lens
• Saving and Loading Scene States
• Render Options
• Statistics

1 Introduction

ecmview is a tool to view ECM databases interactively.

ECM (Ellipsoidal Cube Map) databases store data for the surface of a planetary object, for example photos and elevation models of Earth, Moon, or Mars.

For more information about ECM, see http://ecm-planet.sourceforge.net/.

The ecmview tool is based on OpenGL, and is targeted at powerful graphics hardware. Please note that ecmview is a research prototype and not a polished end user product. It is neither a fully-featured planet viewer nor a performance-optimized terrain renderer.

2 Accessing ECM Databases

To open an ECM database on your disk, use "File -> Open local data set" and choose its directory.

For ECM databases that are available via the network, use "File -> Open remote data set" and specify the URL, and optionally a user name and password. Supported protocols include HTTP and FTP; see the documentation of the libcurl library for more options.

There are currently three categories of databases:

1. Elevation databases. Elevation data defines the geometry.
2. Texture databases. This category is meant for common image data, e.g. orthophotos.
3. SAR amplitude image databases. SAR images are converted to color or gray level images during rendering.

Opened databases will appear in the database overview in the lower left corner of the main window. You can double click on a database to open its property dialog. With a right click, you get the option to close a database.

There is one special database named "Texture from elevation". This database is always open, but not active by default (you can activate it in its property dialog). This special database will create texture data from the available elevation data at rendering time. This is useful e.g. to use color ramps for terrain or to create isolines dynamically.

3 Processing and Combining Databases

The property dialog of a database provides two tabs called "Global parameters" and "Lens parameters". These tabs provide the same set of options. For now, only the "Global parameters" tab is of interest. See Lens for more information about the "Lens parameters" tab.

In the parameters tab, you can do the following:

• Activate or deactivate a database.
  Deactivated databases will not be displayed.
• Set the database priority.
  Databases with higher priorities will override databases with lower priorities in the rendered image. Databases with the same priority will be blended according to adjustable blend weights (see next option).
• Set the database weight.
  You can adjust how databases with the same priority are blended by giving them different weights. For example, a database with weight 0.8 will have double influence on the rendered image compared to a database with weight 0.4. This is useful for overlay effects. You can for example overlay generated isolines from the "Texture from elevation" special database over some texture database.
• Adjust processing options.
  Different database categories provide different processing options. Processing is performed on the GPU during rendering. For example, you can scale elevation data and immediately see the result in the rendered image. Texture data can be color-adjusted. SAR images can be despeckled, and dynamic range reduction can be applied.
  The special database "Texture from elevation" allows you to define color ramps for elevation data and/or to generate isolines. Note that this texture generation is applied after the final elevation is composed from the input databases, so changes in the processing parameters of the input elevation will immediately also affect the result from the "Texture to elevation" database.

4 Navigating

Use the mouse to navigate. Press one of the mouse buttons while moving the mouse: a left click rotates the planet, a middle click translates, and a right click zooms. The mouse wheel moves the viewer forward/backward along the view direction.

Holding the Shift key down while navigating slows down all navigation actions, and holding the Ctrl key down accelerates all actions.

(The navigation currently is not very friendly and needs to be improved.)

5 Lighting

You can apply a simple directional light to your scene by activating Lighting in the GUI.

You have two options to position the light source: global or relative to the viewer.

Simply experiment with the GUI to find out how things work.

6 Lens

A lens is a circular area on the reference ellipsoid in which different databases can have different parameters than on the rest of the ellipsoid.

That's why there is both a "Global parameters" and a "Lens parameters" tab in the database property dialog.

You can activate and position the lens in the GUI. Once active, you can move the lens around by holding the Meta key down (on many keyboards, this is the Windows key) while moving the mouse. Using the mouse wheel while holding Meta will change the size of the lens. As in navigation, these actions can be slowed down by also holding the Shift key down, or accelerated by also holding the Ctrl key down.

7 Saving and Loading Scene States

You can save the complete scene state from the File menu and later reload it. The scene state includes opened databases and their parameters, light and lens state, and the viewer position and orientation.

8 Render Options

You can display an options dialog via "Dialog->Toggle Options".

• The "Max. quad screen space ratio" and "Quad subdivision level" settings define the level of detail. See the ECM paper for details.
• The GPU cache size should be about half of your graphics memory, and the main memory cache size should be about half of your RAM.
• Simply experiment with the other options to see what they do.

9 Statistics

You can display a renderer statistics dialog via "Dialog->Toggle Statistics".

This shows the current FPS rate as well as information about the rendered quads.