Lighting on 3D Objects - Page 4

The light source

The light source is symbolized by xm and ym. These coordintates either represent the coordinates of the mouse, or are put on the path of a function. For this path I chose a deltoid. I found this function on this page written by Paul Bourke in 1990.
I made a button to switch between 'manual' and 'automatic', the if statements handles that. The variable i represents theta needed to make steps in the deltoid function.
The _root.light mc is a white circle representing the light source.

// making the light move -----
i++;
if (i >= 360) { i=i - 360 }
// must be in radians (not degrees)
theta=(_root.convrad) * i;
// -------------------------------

// path of lightsource -----------
if (_root.lightsource == "manual") {

	xm = _root._xmouse;
	ym = _root._ymouse;

} else if (_root.lightsource == "automatic"){

// you can replace this function for any other you like better 

	xm = xb + (2 * a * Math.cos(theta) + a * Math.cos(2 * theta));
	ym = yb + (2 * a * Math.sin(theta) - a * Math.sin(2 * theta));
}
// -------------------------------