One nifty trick for navigating around Nviz is the "paste" feature supported in Tcl/Tk menus. Any pulldown menu may be pasted permanently on the screen by selecting the menu using the middle mouse button (as opposed to the first mouse button). The user may then click and drag the menu to another location on the screen. The menu will remain in its new position, regardless of the selections made from it, until the menu item which created the pulldown is selected using the first mouse button. For example, you can keep the "Panel" menu up for the duration of an Nviz session by selecting "Panel" from the main menu using the middle mouse button. Selecting "Panel" with the first mouse button moves the pasted menu back to its normal position and removes the menu after a selection has been made.
Lighting greatly enhances the level of detail that can be seen in the surface. For good lighting effects, position the light so that it creates a tilted half-moon on the sphere. Usually placing the light in the N-W corner when viewing from the south works well because of the way humans tend to interpret shading. To reveal very subtle gradual elevation changes, experiment with light placement and surface reflectivity. Keep resolution higher (3 or 4) while adjusting viewing position and lighting so that drawing time is fast. Then lower polygon resolution to 1 or 2 for the final rendering of the surface.
When rendering frames for animation, it is usually better to position lights so that they do not move with the viewer position (toggle Follow Viewpoint OFF).
What follows is an example of creating an animation to help you get started.
Using key frames is one of the easiest methods of animation it just takes some getting use to the Key Frame slider. For practice, just try making a circular path while always looking at the center of the data:
You should now have enough key frames marked to define a path, so try clicking on show path and then run (NOT run and save images). If nothing happens, clear all key frames and go back to step 1. Now let's complete the circular path:
Changing key frames: With the above key frames loaded, try changing a key frame as follows:
1........2..3..4
Run again, notice how movement speed was affected.
Because .rgb image files can end up taking a lot of disk space, users should be mindful of disk storage capacity when attempting to create an animation. Keeping animation files and image dumps in directories dedicated for such files helps in management. A single rgb image usually takes between 200K to 3M bytes of storage, depending upon size and complexity. If you use the SGI movie program to replay animations, each frame of the animation must have been saved to files of identical dimensions; so especially if you are creating an animation piecewise, at different sessions, it becomes important to maintain a consistent size for the graphics window. With the movie program and with other screen dump animating programs, there is a zoom option to enlarge the animation images at time of playback. So if you want the animation to fill your screen, you could set the width and height of the graphics window to half or a third their playback sizes when writing the image files, then use the zoom option (this will cause a loss of resolution though, since the zoom just replicates pixels). If you are making an animation to be recorded onto video tape, it may be necessary to set the width and height to specific dimensions.
New SGI programs released with IRIX 4.0.5, moviemaker and movieplayer, are also very useful for animations. Moviemaker allows you to create movie files from any number of rgb files at various frame rates. With movieplayer, much longer animations may be replayed than with movie since the frames are read directly from disk at run time rather than having to be loaded into memory.