Click on the appropriate link below to skip immediately to later parts of this module. If this is your first time through the module, you should go through it in order without using the links below.
This module is about lighting and shading -- two ways that artists convey a sense of depth, of three dimensionality, even when they are drawing on two dimensional paper -- two kinds of clues that our brains use to construct three dimensional images of the world using information from the two dimensional retinas in our eyes. We begin with some experiments. Click here to open a new window with a Java applet. Arrange the two windows so that they overlap and you can move back-and-forth between the two windows by clicking on the exposed portion of the inactive window to make it active.
This Java applet shows a sphere illuminated by a single light source. When this applet starts the light source is lined up with the viewer -- that is, the light is coming from directly behind the viewer. The viewer (you) is conveniently transparent and casts no shadow.
Describe the sphere in the Java applet -- Is it shiny? -- or is it dull or matte? Which parts of the sphere appear brightest? Why do you think that some points appear brighter than others?
You can change the location of the light source in the applet by using the control on the right of the applet. The control is shown in the picture below but it is not "live" in the picture. You will need to use the real control in the applet itself to change the lighting.
| If you click anyplace along the edge of the control the light source will be moved to the same level as the sphere and will illuminate it from a point directly to the north, south, east (your right) or west (your left). How do you think the sphere will look when it is illuminated from different positions? Experiment using the applet to see if your intuition is right. By clicking at different places within the applet's lighting control you can move the light source almost anyplace you would like. When the control is set more toward the center, the light source is more behind you, the viewer. Experiment some more with the light source in different locations to see how the position of the light source affects the appearance of the sphere. |
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Compare the pictures you can create in this way with the pictures of the phases of the moon in Multivariable Calculus, Linear Algebra, and Differential Equations in a Real and Complex World.
When you are done experimenting with this applet close its window and click on the icon below to move on to the next part of this module.
