Light Source Type

Directional: Directional light has color and direction that you can control, but not position. The light it generates is referred to as parallel light; that is, all directional light travels through an object in the same direction.

To specify directional light direction using the mouse

1. Activate Enable Diffuse Lighting.

2. Activate Setup Light.

3. Under Light Source Type, activate Spot.

4. Click OK.

In the plot window, a light directional symbol appears. This symbol represents the light direction. In the upper left corner of the plot window, the x, y, and z coordinates of the direction of the light source are displayed.

5. To control position of the light directional symbol, hold down CTRL+click and drag the mouse.

As you drag the mouse the light directional symbol moves accordingly and sheds light on the 3D object appropriately.

Point: Point light has color and position that you can control; however, it has no single direction. That is, it gives off light equally in all directions.

To specify point light position and range through the dialog box

1. Activate Enable Diffuse Light.

2. Under Light Source Type, activate either Point or Spot.

3. Enter the Light Position coordinates under X, Y, and Z.

4. Under Range, enter a value that indicates how far the light travels.

5. Click OK.

The plot window will reflect the light position you have specified and light the object accordingly.

Spot: Spot light has color, position, and direction that you can control. The light emitted from a spot light has a narrowly focused inner cone of light as well as an outer cone of light. The light intensity diminishes as it reaches the outer cone, and there is no light beyond the outer cone. To control the size of the inner and outer cones, the elements Phi and Theta are used. The following illustration shows the relationship between these elements:

To specify spot light position, direction, range Phi, and Theta through the dialog box

Note: You can only enter the range, Phi, and Theta values through the dialog box.

1. Activate Enable Diffuse Light.

2. Under Light Source Type, activate Spot.

3. Enter Light Position coordinates in the corresponding X, Y, and Z text boxes.

4. Enter the Light Direction coordinates in the corresponding X, Y, and Z text boxes.

5. Enter the range, Phi, and Theta values in the corresponding text boxes.

6. Click OK.

The plot window will reflect the light position you have specified and light the object accordingly.

To specify spot light position and direction using the mouse

 

1. Activate Enable Diffuse Lighting.

2. Activate Setup Light.

3. Under Light Source Type, activate Point.

4. Click OK.
In the plot window, a positional/directional symbol appears, which represents the light source. In the upper left corner of the plot window, the X, Y, and Z coordinates of the position and direction of the light source are displayed.

5. To control the position of the light source, hold down CTRL+right-click and drag the mouse. As you drag the mouse the symbol moves accordingly and sheds light on the 3D object appropriately.

6. To control the direction of the light source, hold down CTRL+click and drag the mouse. As you drag the mouse, the arrow attached to the  symbol moves accordingly and sheds light on the 3D object appropriately.