NOVA Online (click here for NOVA home)
Runaway Universe
Top Ten Things to Know About VRML
back to Preparing Yourself and Your Computer for VRML

This is a quick run-through of the 10 things you need to know in order to successfully navigate your way around the "Local Universe in 3-D" VRML world. This is not a complete tutorial in using a VRML browser plug-in. Resources are listed in the Appendix section for those seeking more information.

The instructions are specific to the CosmoPlayer 2.1 browser plug-in, but the concepts are generally applicable.
  1. VRML Browser Basics
  2. Clickable Objects - "Local Universe in 3-D" controls
  3. Viewpoints - Self-guided tours
  4. Fly Mode - A virtual spaceship
  5. Fly Mode details - The ups and downs
  6. Examine Mode - The world is your oyster
  7. Examine Mode Details - Finding your center
  8. Seek Button - To boldly go ...
  9. Tips and Tricks
  10. VRML Bugs - Even virtual reality needs exterminators
    Appendix: VRML Resources

1.  VRML Browser Basics
The first thing to know is the layout of the VRML browser. The following screen shot illustrates a VRML browser window and its two major frames.

Tour frames

World Frame - This is where the 3-D VRML world is displayed.

Control Frame - This area contains the navigation controls for interacting with the VRML world.

You generally will use your mouse to control or interact with the VRML world. Things in the Control Frame usually require a single click with the left mouse button to activate them. In the World Frame, left, right and center mouse buttons can be used, generally with a "click and drag."

For convenience, keyboard equivalents are provided for some actions. These involve using the arrow keys along with the "Ctrl" and "Alt" keys. We will note such keyboard equivalents in brackets, such as "[Alt-up arrow]."

2.  Clickable Objects: "Local Universe in 3-D" controls
In addition to the controls provided by the VRML browser, we have provided a few simple controls within the VRML World. These controls are provided by "clickable objects."

Clickable Objects
Certain 3-D objects in the VRML world are clickable. When you put the mouse over them and click, something happens.

To let you know that an object is clickable, the mouse pointer changes. In CosmoPlayer 2.1, the mouse pointer looks like a sunburst pattern when an item is clickable.

Not clickable
The mouse pointer (lower center) in the above image is not over the galaxy.

The mouse pointer in this image is over the galaxy and has changed to indicate the galaxy is a clickable object.

"Local Universe in 3-D" Clickable Objects
  • At the Control Panel Viewpoint, there are two buttons labelled "Galaxies" and "Clusters". Clicking the Galaxies button turns on/off the galaxies in the VRML world. Clicking the Clusters button turns on/off the blue spheres indicating the approximate extent of clusters of galaxies. Use these buttons when you want to explore only one type of object. Turning off galaxies or clusters can also speed up the response ot the VRML browser.

  • Also at the Control Panel Viewpoint is a "Help" button. Clicking the Help button brings up this page in a new window.

  • All galaxies are clickable when you are near enough. Clicking a galaxy opens a new window that displays the astronomical data about that galaxy. Also note that when you pass the mouse pointer over a galaxy, the galaxy's name appears in the lower left of the Control Frame.

3.  Viewpoints: Self-guided tours
You arrive in a new place. How do you choose where to go? The easiest way is to let someone else do the work for you. Viewpoints in VRML worlds are places of interest selected by the folks who created the world. These are the places that they think you will want to visit.

Moving between Viewpoints involves only mouse clicks in the Control Frame. The Viewpoint controls on the left side of the Control Frame allow you to go forward and backward among a list of Viewpoints, as well as jump directly to any Viewpoint in the list.

For a self-guided tour, jump to the next Viewpoint and explore a bit. Ready to move on? Then go on to the next Viewpoint. After the last Viewpoint, you will be taken back to the first Viewpoint.

Viewpoints are also critical if you get lost. No matter how confused you are about which way is up, going to a Viewpoint will automatically return you to a defined place. Once you get your bearings at a Viewpoint, you can proceed to get lost again without any worries.

next viewpoint
To move to the Next Viewpoint, click the right-pointing triangle as shown above. The keyboard equivalent is [Page Down].

previous viewpoint
To move to the Previous Viewpoint, click the left-pointing triangle as shown above. The keyboard equivalent is [Page Up].

return to viewpoint
If you move away from a Viewpoint, then the left-pointing triangle returns you to the current Viewpoint. Again, the keyboard equivalent is [Page Up].

viewpoint list button
Clicking the button show above will bring up a list of all the Viewpoints in the VRML world.

viewpoint list
Here is a sample Viewpoint list. When it is displayed, simply click on any of the names to go to that Viewpoint.

4.  Fly Mode: A virtual spaceship
If you want to do more than just go from Viewpoint to Viewpoint, you've got to learn to navigate in the VRML world. Fly Mode is the best place
To understand Fly Mode, imagine you are at the helm of a virtual spaceship. The spaceship can move forward/backward, up/down, left/right through the world. It can also turn left/right as well as pitch forward/back. When you work the controls, your view of the world represents what is seen in the forward direction from your virtual cockpit.

Fly mode control panel
Fly Mode

This is what the central part of the Control Frame looks like in Fly Mode. The highlighted button at the top center is called "Go."

Go control panel Go button
Go cursor Go mouse pointer

If Go is not active, click on the Go button. The mouse pointer will change to the same icon as on the Go button. To move forward, click in the World Frame and drag up. To move backward, click in the World Frame and drag down. If you click and drag left/right in the World Frame, you will turn left/right. The arrow keys are keyboard equivalents for these motions.

Fly Mode - Go Summary
Motion Mouse Action in World Frame Keyboard Equivalent
move forward click and drag up up arrow
move backward click and drag down down arrow
turn left click and drag left left arrow
turn right click and drag right right arrow

Go is the easiest to learn because it is not really 3-D. Moving forward, backward, left, and right moves you only in a 2-D plane. You can't move up or down from this plane.

5.  Fly Mode Details: The ups and downs
In Fly Mode, there are two other navigation buttons to the right and the left of the Go button.

Slide control panel Slide button
Slide cursor Slide mouse pointer

On the right is the Slide button. Clicking it will change the mouse pointer to the same icon as on the Slide button. Think of Slide as an elevator that can go both up/down and left/right. Like Go, the motion in Slide is also within a 2-D plane, but one that is perpendicular to the Go plane of motion. One can navigate quite well in a VRML world using only Go and Slide. Use Go to walk the floors of a building, and Slide to take the elevator between floors.

Fly Mode - Slide Summary
Motion Mouse Action in World Frame Keyboard Equivalent
move up click and drag up up arrow
move down click and drag down down arrow
slide left click and drag left left arrow
slide right click and drag right right arrow

Tilt control panel Tilt button
Tilt cursor Tilt mouse pointer

The Tilt button is the one on the left, and by now you should be able to guess what the mouse pointer will look like. Tilt only adjusts the orientation of your virtual spacecraft. Tilt up to pitch back, and tilt down to pitch forward. Left and right are the same as Go; turn left/right.

When you use Tilt up/down, you change the plane of your orientation. If you then switch back to Go, you will travel on a new plane, one at an angle to the previous one.

Fly Mode - Tilt Summary
Motion Mouse Action in World Frame Keyboard Equivalent
tilt up click and drag up up arrow
tilt down click and drag down down arrow
turn left click and drag left left arrow
turn right click and drag right right arrow

straighten button
Straighten Button

Tilt can also be used to just look up/down and survey your surroundings. When you want to return to an "untilted" view, click on the Straighten button as shown above.

6.  Examine Mode: The world is your oyster
Fly Mode moves the viewer from place to place within the VRML world. You imagine yourself as a tiny part of the virtual space, and navigate through it.

Now imagine yourself as much bigger than the VRML world, a virtual giant. You see this VRML world as a small object that you wish to study. You pick up the world, move it around, bring it closer, and turn it over for inspection. This way of viewing a VRML world is called Examine Mode.

In Examine Mode, the essential idea is that you, the viewer, are stationary. When you click and drag with the mouse, you are moving the VRML world. For example, when you find an interesting object in a VRML world, you switch to Examine Mode in order to zoom in on it and to rotate it and view it from every angle.

Change Controls Button
Change Controls Button

To change the controls from Fly Mode to Examine Mode, click on the Change Controls Button as shown above. The three buttons of Fly Mode (Go, Slide, and Tilt) will be replaced by three buttons for Examine Mode. Everything else that has been discussed above stays the same.

Examine Mode Controls
Examine Mode Controls

This is what the central part of the Control Frame looks like in Examine Mode. The three buttons are now Zoom, Rotate, and Pan (from left to right). Rotate is the default action in Examine Mode, but we'll discuss that last. Zoom and Pan are similar to Go and Slide.

Zoom control panel Zoom button
Zoom cursor Zoom mouse pointer

The left button in Examine Mode is Zoom. The mouse pointer for Zoom is the same icon as on the Zoom button, which is similar to the Go icon in Fly Mode. Not surprisingly, Zoom has similar function to Go. When you zoom in, you move the world closer. Zooming out moves the world farther away. In practice, it feels the same as the viewer moving forward and backward through the world. However, one cannot turn left or right in Zoom.

Examine Mode - Zoom Summary
Motion Mouse Action in World Frame Keyboard Equivalent
zoom in
move world closer
click and drag up up arrow
zoom out
move world further away
click and drag down down arrow
click and drag left
click and drag right

Pan control panel Pan button
Pan cursor Pan mouse pointer

On the right is the Pan button. Clicking it will change the mouse pointer to the same icon as on the Pan button. Pan is the same as Slide, except that now the world moves up/down and left/right. You use Pan to put the object of interest at the center of your screen.

Examine Mode - Pan Summary
Motion Mouse Action in World Frame Keyboard Equivalent
move world up click and drag up up arrow
move world down click and drag down down arrow
slide world left click and drag left left arrow
slide world right click and drag right right arrow

7.  Examine Mode Details: Finding your center
With Pan and Zoom, you can move an object of interest to the center of your screen and bring it close. Then you use Rotate to study it from all sides. That is how it is supposed to work. Unfortunately, there is a problem that requires some extra work.

Rotate control panel Rotate button
Rotate cursor Rotate mouse pointer

The center button in Examine Mode is Rotate. Yet again, the mouse pointer is the same icon as on the button. Rotate spins the VRML world. The axes of rotation are always relative to the viewer. You can spin the world up/down and left/right as you see it. Rotate does not care about any X/Y/Z axes defined in the world. The viewer is in control.

Examine Mode - Rotate Summary
Motion Mouse Action in World Frame Keyboard Equivalent
rotate world up click and drag up up arrow
rotate world down click and drag down down arrow
rotate world left click and drag left left arrow
rotate world right click and drag right right arrow

Problem: Where is the center of the rotation?
If you are rotating the VRML world, that implies that everything is spinning around some center point. If you are zoomed out and studying the entire VRML world, you want the center point to be in the middle of the world. If you are zoomed in and studying one particular galaxy, then you want the center point to be at the center of that galaxy.

How does one tell the VRML browser where to put the center point?

First of all, we, the designers of the VRML world, can not define a center point. The center point in Examine Mode is officially undefined in the VRML specification (we consider this a major bug). The VRML browser is free to define a center point based on its best guess.

So, you, the viewer must help the VRML browser to define a good center point for what you want to do. You can do this in two ways.
  1. Viewpoint Binding: For each Viewpoint, the VRML browser chooses a center of rotation. You can go to each Viewpoint in Examine Mode and Rotate the world. That will show you the selected center. Sometimes the VRML browser chooses well, sometimes not. If you find a Viewpoint with a good center, you can Zoom in/out and Rotate about that center. (Note that Pan shifts the center of rotation, so that using it can be confusing.) Some examples in the "Local Universe in 3-D" VRML world are:

    • Milky Way Viewpoint: The center of rotation is the center of the coordinate axes (where the bright red, green, and blue lines meet). Zoom out from here until the whole VRML world is visible. Then you can rotate the world in front of you and examine it like a globe.

    • Local Group Viewpoint: This one behaves exactly as you would hope/expect. The center is the center of the Local Group sphere. This is good for examining the nearby clusters of galaxies.

  2. Seek Button: Using the Seek button (see next section), one can tell the VRML browser which object to put at the center of rotation. In general, you must get very close to the object for the VRML browser to select it as the center of rotation. You may have to use the Seek button a couple times before the desired center of rotation is selected by the VRML browser. Then, you can Zoom out and Rotate it. We'll discuss Seek Button in detail in the next section.
Setting the center of rotation is probably the most frustrating thing in VRML. You can be positioned perfectly around a cluster of galaxies, and then when you use Rotate, the whole thing spins wildly away from you. It takes some practice.

8.  Seek Button: To boldly go ...
There is one last navigation button that we will discuss here, the Seek button. A couple other buttons remain, but they are for a complete tutorial, not a Top 10 list.

Seek control panel Seek button
Seek cursor Seek mouse pointer

The Seek button is located to the left of the central buttons. When you click on the Seek button, the mouse pointer changes to the icon on the Seek button. You then can click on any object in the VRML world, and the VRML browser will bring your view closer to that object. You get only one Seek click, after that, the navigation and mouse changes back to whatever central button is active.

Some notes:
  • Sometimes one click won't bring you near enough to an object, and you need to repeat the Seek.

  • Sometimes the browser won't understand which object you are clicking on. This happens a lot when the object is far away. Use the other navigation controls to get reasonably close. Use Seek to finish the job.

  • If an object is inside another object, like a galaxy within a transparent cluster sphere, you cannot click on it to Seek. The VRML browser takes the first object underneath the mouse as the Seek object.

  • When you do a Seek, the center of rotation changes to the object clicked. Sometimes you have to do multiple Seeks to get the center of rotation where you want it. Also, for big spheres (like the bigger galaxy cluster spheres) the center of rotation may not go to the center of the sphere. It may go to a point on the near surface of the sphere. You can not do anything about this. Go into the cluster and Seek a galaxy near center. Then Zoom out and Rotate the cluster.

9.  Tips and Tricks
On the far right of the Control Frame there is a Help button:

Help Button

Clicking this button brings up CosmoPlayer's instructions web page in a new window. They have a little game called Chomp that you can play to get acquainted with the controls. Their instructions are rather limited, which is why we created this Top 10 list.

Also on the far right of the Control Frame is the Preferences button:

Preferences Button

Clicking the Preferences button brings up the Preferences window, as shown below:

Preferences window
Preferences Window

In the Preferences window, you can set all sorts of parameters. You can also crash your VRML browser (see VRML Bugs below). The two most important preferences are the Navigation Speed (shown above) and the Graphics Renderer Selection (shown below). Change the Navigation Speed to slower when you want fine control over your movement. (By the way, do not turn off the Headlight or you won't be able to see the galaxy cluster spheres.)

Renderer selection
Renderer Selection

Be very careful when using Renderer Selection. Your VRML browser and/or your computer may crash. Save before changing. We present this panel because there are bugs in how the renderers (the programs that draw the graphics on your screen) communicate with the VRML browser. Sometimes, the renderer may try to do things so quickly that it forgets to draw something. Sometimes it draws things but makes them too faint to see (for example, the cluster spheres). You may want to try different choices here and see how they look and perform. Note that software-only rendering will generally produce a consistent look, but it will be much slower (especially if you have a 3-D graphics card).

  • If you get lost, go to a Viewpoint to get re-oriented.
  • If you forget which way is up, use the Straighten button.
  • To set a center for Examine Mode, use a Viewpoint or the Seek button.
  • In Fly Mode, the right mouse button or [Alt] activates Slide and the center mouse button or [Ctrl] activates Tilt.
  • In Examine Mode, the right mouse button or [Alt] activates Pan and the center mouse button or [Ctrl] activates Zoom.
Patience: It takes some time to learn how to move in 3-D. Often, you will know what you want to do well before you know how to do it. We have tried to explain the important things here. However, there is a big difference between reading and doing. If you have a slower computer, move slowly through the VRML world to figure out how quickly and smoothly you can move. Once your view starts jumping around, you are trying to navigate too fast.

Resources: To get better performance, close unnecessary programs. That will free up more processor cycles and memory for the VRML browser. Further, if things crash, you won't lose your work in other programs. On Macs, you may need to increase the amount of memory available to your Internet browser (48 or 64 MB seems to be needed).

Explore: This is not scripted entertainment like a TV show or a movie. There are some viewpoints for you to visit, but the rest is up to you. Your curiosity and sense of exploration are far more important in enjoying a VRML world than the intentions of the world's designers.

10.  VRML Bugs: Even virtual reality needs exterminators
All Platforms
  • Designers of a VRML world cannot set the center of rotation in Examine Mode for Viewpoints. The VRML browser makes a guess.

  • The developer of the "Local Universe in 3-D" VRML world has both Windows and SGI computers. He has fixed the problems he could for those platforms. He has relied on second-hand reports for Mac performance. He has not done anything on any other platforms (e.g., Linux).

  • Due to the very wide diversity in graphic cards and installed software on computers, we know there will be other conflicts and bugs out there. We can't fix such bugs. We probably can't even give you good advice on such bugs. We just created a VRML world. We have no control over the VRML browser or your internet browser or your graphics card drivers. About the only advice we can provide is to update to the latest versions and try again.
Windows 95/98
  • On one computer, CosmoPlayer would run fine once, then it crashed the Internet browser. If you loaded a second VRML world (or re-loaded one), or even just loaded a web page in that window, it would complain of illegal activity and shut down the internet browser. This computer had Nvidia Riva TNT2 video card, and the problem appeared to disappear when we switched to the Direct3D renderer. We're not exactly sure why the problem went away.

  • Switching renderers can crash the VRML browser window. You click "OK" and the Preferences window doesn't disappear. The whole VRML browser window stops responding. Use Ctrl-Alt-Del (once, not twice) and select "End Task" for that window. Reload the VRML world and the new renderer should be in effect.

  • The OpenGL renderer often optimizes out the buttons (and text) at the Control Panel Viewpoint. Moving slightly forward or back can bring these elements back. Other renderers don't seem to have this problem.

  • The Direct3D renderer showed a strange bug on one machine where the far away galaxies (drawn as points) only appeared on the left half of the screen. This computer had a Voodoo 3 2000 PCI graphics board.
  • The Mac version of CosmoPlayer was never fully released. Development was stopped in Beta version.

  • On some Macs, most of the galaxies do not show up at the Overview Viewpoint. However, once you fly into the grid, they re-appear.

  • The "Local Universe in 3-D" VRML world has been known to crash Macs. Cause is unknown at this point.
  • CosmoPlayer 1.x is installed by default on SGIs. You must have CosmoPlayer 2.x to view the "Local Universe in 3-D" VRML world.

  • On certain machines, the "Local Universe in 3-D" VRML world will take over a minute to load. On other, similarly equipped machines, it takes only 20 seconds. Once the words "Document: Done" appear, it can take up to 90 seconds for the graphics to appear.

Appendix: VRML Resources
The Web3D Consortium web page is not that useful, except for the VRML Repository. They sponsor the Web3D Symposium and the Web3D Round-Up at SIGGRAPH: has a great resource for VRML and Web3D. Especially useful is the VRML browser datasheet:

VRMLWorks is a great site for all sorts of information including help on selecting a browser, lots of worlds to browse, and advice on how to build VRML worlds:

TECFA has a long list of links to VRML web sites:

Finally, for those who want the details, the Online Annotated VRML 97 Reference is based on one of the most popular books about VRML:

History of the Universe | Birth of a Supernova | Tour the Universe
Moving Targets | How Big is the Universe? | Spin a Spiral Galaxy
Resources | Transcript | Site Map | Runaway Universe Home

Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule
About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print
PBS Online | NOVA Online | WGBH

© | Updated November 2000
/wgbh/nova/universe/textindex.html /wgbh/nova/universe/