This command initiates a dialog that allows the user to control various aspects of the lighting model used for rendering. There are 3 basic controls in this dialog box.
The Brightness control along the right hand side of the dialog box is a standard scroll bar that allows the setting of the overall brightness of the the light source. Its operation is self-explanatory.
Like the Brightness control, the Ambient Light control is a standard scroll bar. This control affects the minimum level of illumination on a surface that would normally receive no light from the light source. Setting this control to zero would cause such a surface to be rendered true black (assuming no haze).
The most interesting control is the large control that dominates most of this dialog box. The operation of this control is pretty simple. By clicking and dragging on the knob of the “stick” you can tilt this stick about a full hemisphere. There are two ways to move this “stick” between the front and rear hemispheres. First, click on the stick and hold the mouse button down. Then, keeping the mouse button depressed, simply move the cursor well outside of the control circle. Still keeping the button depressed, move the cursor back into the control circle and the stick will have flipped to the other hemisphere. To return to the prior hemisphere, just repeat the process.
The second method is even simpler. Clicking on the non-highlighted of the two radio buttons at the top of the control area will also cause the stick to flip hemispheres.
Simply move the stick such that the stick itself represents the desired vector for the illumination direction. That is, the vector from the knob of the stick to the rectangular polygon to which the stick is attached will represent the vector for the light source.
