AstroGrav Help /Tutorial /Exercise 3 - Using View WindowsVersion 5.2.1

Exercise 3 - Using View Windows

This exercise teaches you how to use view windows, and should take about 20 minutes to complete.

Opening the Tutorial Simulation

If you already have the Tutorial simulation open, choose the File / Revert to Saved menu item, which will return the simulation to the same state that it was in when you first opened it. Otherwise, go through the following steps to open it.

If you don't already have AstroGrav running, double-click on the AstroGrav application icon () to start it running.
When the Open Simulation file chooser dialog is displayed, navigate to and open the Tutorial.ast file.
The Tutorial simulation will then open, and you will see the simulation's three windows displayed on your screen.

The Tutorial: View window should be the frontmost window, but if it isn't, click on it to bring it to the front. This window is a three-dimensional interactive model in which you will see the Sun and the five innermost planets - Mercury, Venus, Earth, Mars, and Jupiter. This exercise will show you how to manipulate this three-dimensional interactive model and navigate around it.

Navigating With the Mouse

Go through the following steps to learn how to navigate around view windows.

Drag the mouse pointer around the window, without holding down any of the modifier keys, and watch how the view changes to allow you to look in different directions. Your viewpoint remains the same while you look in different directions, as if you were turning your head while remaining in the same position.
Now, hold down the Alt key, and drag the mouse pointer around the window, and watch how the view rotates clockwise and anticlockwise. Your viewpoint remains the same while your view rotates. so that you can view the system on its side or upside down.
Now, hold down the Shift key, and drag the mouse pointer around the window, and watch how the solar system rotates about the Sun, so that you can see it from different directions.
Now, hold down the Control key (Command key on a Mac), and drag the mouse pointer around the window, and watch how your viewpoint moves towards and away from the Sun. Dragging the mouse pointer towards the upper-right moves you towards the Sun, and dragging the mouse pointer towards the lower-left moves you away from the Sun.

Combining the Four Different Mouse Dragging Operations

You have now learnt the following four different mouse dragging operations.

Looking around, by dragging the mouse pointer.
Rotating the view, by dragging the mouse pointer while holding down the Alt key.
Rotating the system, by dragging the mouse pointer while holding down the Shift key.
Moving to/from, by dragging the mouse pointer while holding down the Control key (Command key on a Mac).

Spend a minute or two experimenting with these different operations, until you feel confident that you can use them to obtain any view that you want. Notice how rotating the system is a very good way to obtain a three-dimensional impression of the system.

Selecting Objects

In order to view or edit the details of an object (covered in a later exercise of this tutorial), it is necessary to first select the required object. Go through the following steps to learn how to select and deselect objects, and view some of the information about the selected object.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Select the Earth by clicking on it without holding down any of the modifier keys, and check that its orbit has been highlighted. If it hasn't been highlighted, your click was probably not close enough to the Earth, so try again until the Earth's orbit highlights. You will see that the Earth's distance, speed, magnitude, and phase are now displayed next to it.
Now, select Venus by clicking on it without holding down any of the modifier keys, check that its orbit highlights, and see how its distance, speed, magnitude, and phase are displayed next to it.
Now, select the Sun without holding down any of the modifier keys, and notice how there is now no orbit highlighted because the Sun is the central object in the system. Its "phase" information is also missing because phases apply only to non-luminous objects (such as planets) and not to luminous objects (such as stars).
Now, click between the Sun and the Mars, and then click somewhere in the area above and to left of Earth while holding down the Shift key, and notice how the deselected objects in the rectangular area between your clicks have been selected and the selected objects have been deselected. Clicking while holding down the Shift key is used to select and deselect entire blocks of objects. You may need to select multiple objects in order to copy, delete, or merge them, as well as to view their distances, speeds, angular diameters, magnitudes, phases, and phase angles.
Click on several objects in turn while holding down the Control key (Command key on a Mac), and notice how deselected objects become selected and selected objects become deselected.
Choose the Edit / Select All menu item, and notice how all of the objects are now selected. Then choose the Edit / Deselect All menu item, and notice how all of the objects are now deselected.
Finally, experiment with combinations of the previous steps until you are able to quickly select and deselect whatever combination of objects you want.

Fixing an Object

When rotating the system, moving towards or away from the Sun, and evolving the simulation, you have probably noticed that the Sun remains fixed in position while everything else moves. This is indicated on the status bar by the "Fixed: Sun" entry. Go through the following steps to learn how to change the object that is fixed in position while performing these operations.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Click on the Earth while holding down the Alt and Shift keys, and check that on the status bar, the Earth has now replaced the Sun as the fixed object.
Now, hold down the Shift key, and drag the mouse pointer around the window, and notice how the Earth now remains fixed in position while everything else rotates about it.
Now, hold down the Control key (Command key on a Mac), and drag the mouse pointer around the window, and notice how your viewpoint now moves towards and away from the Earth instead of towards and away from the Sun.
Choose the Evolve / Run Forward menu item (or the tool), which will start the simulation running forward in time. Notice how the Earth now remains fixed in position while everything else moves.
Finally, stop the simulation running by using the Evolve / Stop menu item (or the tool).

You can also set the fixed point by using the View / Fix... menu item (or the 'View / Fix...' icon tool) or by clicking anywhere in the window where there are no objects present while holding down the Alt and Shift keys. When you do this, a dialog is displayed giving you several different choices. The Barycenter option is particularly useful, as it makes the center of mass the fixed point, instead of one of the objects. In the case of the Tutorial simulation, it is difficult to tell the difference between making the barycenter the fixed point and having the Sun as the fixed object, because the center of mass of the Solar System is so close to the center of the Sun.

Next, go through the following steps to see a more practical use for what you have just learned.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Click on Jupiter while holding down the Alt and Shift keys, and check that on the status bar, Jupiter has now replaced the Sun as the fixed object.
Now, drag the mouse pointer around the window, without holding down any of the modifier keys, until Jupiter is near the center of the window.
Now, hold down the Control key (Command key on a Mac), and repeatedly drag the mouse pointer towards the upper-right, watching how your viewpoint moves towards Jupiter until its four moons become visible, and the largest of their orbits eventually almost fills the window.
Choose the Evolve / Run Forward menu item (or the tool), which will start the simulation running forward in time.
Now, choose the Evolve / Settings... menu item (or the tool), which will result in the Evolve Settings input dialog being displayed.
Change the time step from 1.0 day to 1.0 hour and accept the dialog. Notice how the simulation now runs at a more acceptable speed for viewing the motion of Jupiter's moons.
Experiment with rotating the system, by dragging the mouse pointer with the Shift key, and notice how your view (including the phase of Jupiter) changes. See if you can change the phase of Jupiter to zero, so that the Sun is 'hidden' behind Jupiter.
Finally, stop the simulation running by using the Evolve / Stop menu item (or the tool).

Viewing From an Object

Go through the following steps to learn how to view from a particular object.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Click on Jupiter while holding down the Alt and Control keys (Alt and Command keys on a Mac), and notice how your viewpoint jumps to Jupiter, with "Viewpoint: Jupiter" now being displayed on the status bar.
Now, hold down the Shift key, and drag the mouse pointer around the window, and notice how a dialog appears telling you that rotating the system is impossible while viewing from an object. Cancel this dialog.
Now, hold down the Control key (Command key on a Mac), and drag the mouse pointer around the window, and notice how a dialog appears telling you that moving to/from is impossible while viewing from an object. Cancel this dialog.
Now, drag the mouse pointer around the window, without holding down any of the modifier keys, and watch how the view changes to allow you to look in different directions. Unlike rotating the system and moving to/from, looking around and rotating the view are allowed while viewing from an object because these operations do not move the viewpoint. Position the view so that the Sun is somewhere near the center of the window.
Choose the Evolve / Run Forward menu item (or the tool), which will start the simulation running forward in time.
Now, choose the Evolve / Settings... menu item (or the tool), which will result in the Evolve Settings input dialog being displayed.
Change the time step from 1.0 day to 1.0 hour and accept the dialog. Notice how the simulation now runs at a more acceptable speed for viewing the motion of Jupiter's moons.
Finally, stop the simulation running by using the Evolve / Stop menu item (or the tool).

You can also detach your viewpoint from the object that you are viewing from by using the View / View From... menu item (or the 'View / View From...' icon tool) or by clicking anywhere in the window where there are no objects present while holding down the Alt and Control keys (Alt and Command keys on a Mac). When you do this, a dialog is displayed giving you several different choices. The Floating option detaches your viewpoint from the object that you are viewing from, so that you can once again rotate the system and move to/from the fixed point.

Displaying the Navigation Guide

You will probably have trouble remembering all the mouse click and mouse drag commands, so a navigation guide is provided to remind you. Go through the following steps to learn how to use the navigation guide.

Choose the Help / Navigation Guide menu item, and notice how the Navigation Guide window is displayed.
Study the information provided until you understand it, so that you will be able to quickly use the navigation guide in the future.
Finally, close the Navigation Guide window when you have finished studying it.

Changing the Magnification

Go through the following steps to learn how to change the magnification of a view window.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Check that the field of view displayed on the status bar is very roughly 40°x30°
Now, choose the View / Magnification / Much Larger menu item (or the tool), and notice how the magnification is greatly increased, with a corresponding decrease in the field of view displayed on the status bar.
Now, choose the View / Magnification / Much Smaller menu item (or the tool), and notice how the magnification is greatly decreased, with a corresponding increase in the field of view displayed on the status bar.
Repeatedly choose the View / Magnification / Larger menu item (or the tool), and notice how each time the magnification is slightly increased, with a corresponding decrease in the field of view displayed on the status bar.
Repeatedly choose the View / Magnification / Smaller menu item (or the tool), and notice how each time the magnification is slightly decreased, with a corresponding increase in the field of view displayed on the status bar.

Increasing the magnification seems to have a similar effect to moving your viewpoint towards the fixed object, but they are in fact very different, because when changing the magnification your viewpoint remains fixed. In particular, if you want a clearer view of whatever you're looking at while viewing from an object, you can increase the magnification, whereas moving your viewpoint is not possible.

Changing the Brightness

Go through the following steps to learn how to change the brightness of a view window.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Look at the orbits beyond Jupiter's, and notice that Saturn's orbit (the innermost) is clearly visible, Uranus' orbit (the second innermost) is less clearly visible, Neptune's orbit (the third innermost) is only dimly visible, and Pluto's orbit is not visible at all. This is because at the current brightness settings Neptune is only just bright enough to be visible, and Pluto is not bright enough to be seen at all.
Now, choose the View / Brightness / Much Brighter menu item (or the tool), and notice how the brightness is greatly increased, with Uranus' orbit and Neptune's orbit now clearly visible.
Now, twice choose the View / Brightness / Much Dimmer menu item (or the tool), and notice how each time the brightness is greatly decreased, with Mars' orbit now less clearly visible, Uranus's orbit now only dimly visible, and Neptune's orbit no longer visible at all.
Repeatedly choose the View / Brightness / Brighter menu item (or the tool), and notice how each time the brightness is slightly increased.
Repeatedly choose the View / Brightness / Dimmer menu item (or the tool), and notice how each time the brightness is slightly decreased.

Changing the Object Style

Go through the following steps to learn how to change the object style used in a view window.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Now, choose the View / Object Style / Intermediate menu item (or the tool), and notice how the appearance of the objects is changed. In particular, it is now harder to tell how big the Sun is because its boundary is no longer clear.
Now, choose the View / Object Style / Photographic menu item (or the tool), and notice how the appearance of the objects is changed. The photographic object style is designed to imitate the appearance of astronomical photographs.
Now, choose the View / Object Style / Circular menu item (or the tool), and notice how the appearance of the objects is changed. The circular object style is provided mainly for use with computers that can draw circles much faster than they can draw objects using the other three styles.
Now, choose the View / Object Style / Standard menu item (or the tool), and notice how the appearance of the objects is changed back to the standard object style. The standard object style is ideal for showing both how big objects are and how bright they are at the same time.

Changing the Show Options

There are several "on-off" switches that you can use to change how a view window is displayed. Go through the following steps to learn how to switch them on and off, and to learn what effect they have.

Choose the File / Revert to Saved menu item, which will return the tutorial simulation to the same state that it was in when you first opened it.
Now, choose the View / Show / Barycenters menu item (or the tool), and notice how an indicator of the position of the system barycenter appears on top of the Sun, and indicators of the barycenters of the Earth's and Jupiter's families appear on top of the Earth and Jupiter respectively. Choose the same command again to return the display to its original state.
Now, choose the View / Show / Invisible Objects menu item (or the tool), and notice how the outer orbits have become clearly visible, and the appearance of Jupiter has changed. This command makes any objects that are too faint to see properly at the current brightness setting display as an 'x', with their names and orbits clearly visible. It is an alternative to changing the brightness setting when you are interested in objects that are too faint to see properly at the current brightness setting. Choose the same command again to return the display to its original state.
Now, choose the View / Show / Coordinate Axes menu item (or the tool), and notice how the coordinate axes are now visible. Choose the same command again to return the display to its original state.
Now, choose the View / Show / Magnitude Key menu item (or the tool), and notice how the magnitude key is now visible in the upper-right of the window. Choose the same command again to return the display to its original state.
Now, choose the View / Show / Three Dimensional menu item (or the tool), and notice how the window is now displayed for three dimensional viewing with red/cyan 3D glasses. Choose the same command again to return the display to its original state. If you have 3D glasses with differently colored lenses, you can change AstroGrav's three dimensional display by using the preferences.
Now, choose the View / Show / Inverted menu item (or the tool), and notice how the colors are now inverted. This command is useful if you want to print screenshots without wasting large quantities of printer toner. Choose the same command again to return the display to its original state.
Now, choose the View / Show / Grayscale menu item (or the tool), and notice how the colors are now converted to grays. This command is useful if you want to print screenshots in black and white and want see how it will look beforehand. Choose the same command again to return the display to its original state.
Now, choose the View / Show All / Objects menu item (or the tool), and notice how the objects are now hidden. Choose the same command again to return the display to its original state.
Now, choose the View / Show All / Names menu item (or the tool), and notice how the names of the objects are now hidden. Choose the same command again to return the display to its original state.
Now, choose the View / Show All / Orbits menu item (or the tool), and notice how the orbits of the objects are now hidden. Choose the same command again to return the display to its original state.
Now, choose the View / Show All / Tracks menu item (or the tool), and notice how the tracks of the objects are now shown when you run the simulation forward. Choose the same command again to return the display to its original state.
Now, choose the View / Show All / Velocities menu item (or the tool), and notice how the velocities of the objects are now shown as vectors leading from the objects and pointing in the direction of motion. Choose the same command again to return the display to its original state.
Now, choose the View / Show All / Accelerations menu item (or the tool), and notice how the accelerations of the objects are now shown as vectors leading from the objects and pointing in the direction of acceleration. Choose the same command again to return the display to its original state.
Experiment with various combinations of these "on-off" switches to see the various effects that you can create.

Next: Using Other Types of Windows

You've now completed Exercise 3, and are ready to move on to Exercise 4, which teaches you how to use other types of windows.

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