About Manipulating Light Sources

You can manipulate the light direction by changing the coordinates, rotation angle and the Robot orientation.

The Direction dialog box lets you edit the light direction, the rotation step as well as the quick orientation.

• Direction: the three spin boxes displayed let you define the position of the direction vector along the X, Y and Z directions. The direction vector represents the privileged direction of illumination of the source and is visualized by the red arrow whose origin is the light source origin. As soon as you modify a value, the light source is updated simultaneously in the work area.
• Step-by-Step Rotation: this area lets you define the rotation angle in degrees. The default value is 10.00 but you can enter your own value if needed using the spin box. When the rotation angle has been defined, click the desired button to start rotating your light source around the corresponding axis by the angle you specified.

For example, clicking X+ means that the light source will be rotated by the specified angle positive (i.e. clockwise) around the X axis whereas clicking -X will rotate the light source by the specified angle negative (i.e. anticlockwise) around the X axis:

Starting position: X

New position: X+ Rotation = 45 degrees

Note that using these buttons amounts to manipulating the light source directly in the work area using the Ctrl key.

• Quick Orientation: this area lets you position the light source parallel to the absolute axis system. For instance, clicking Y will modify the light origin in order to position the light source parallel to the Y axis. Inversely, clicking -Y will invert the position of the light source along the Y axis.
• Robot: this button lets you position the light source according to the Robot orientation.

When satisfied, click OK to validate your parameters.

You can modify the intensity of a light source is the maximal lightness value of three colors: Ambient, Diffuse, and Specular.

For detailed information on the Light Source Parameters dialog box, refer to Adjusting Light Source Parameters in the Real Time Rendering documentation.

You can save the user defined light source position.

Once you are satisfied with the position of your light source, click the Save button to store the light position. Each light position is saved under the following name: Direction.n, for instance "Direction.1" for the first position, "n" being incremented by one for each new position you save. You can save as many positions as necessary but keep in mind that you are not allowed to modify the position name.

When finished, click OK to validate.

Important: If you want to use afterwards one of the light positions you saved, just re-select the Save Light Direction contextual command then double-click the desired position: the light position will be updated accordingly in the work area.

Lets you rotate the light source around the absolute axis system.

Using the following options you can rotate the light source around the absolute axis system:

• by default, the Free Rotation contextual command is activated and lets you rotate freely your light source around the X, Y or Z axis using the two green handles
• if you activate the Rotate around X command, you will be able to rotate up or down your light source around the X axis only
• if you activate the Rotate around Y command, you will be able to rotate up or down your light source around the Y axis only
• if you activate the Rotate around Z command, you will be able to rotate up or down your light source around the Z axis only.

When you select the rotation around the X, Y or Z axis, the green handles are hidden and only the light target is displayed: