Add ability to specify light direction and color

[rcmaniac25]

• Ability to specify direction - options.lightPosition
• Ability to specify light color - options.lightColor

[jdan]

Good idea.

isomer.js specifies the direction like so:

/**
 * Light source as defined as the angle from
 * the object to the source.
 *
 * We'll define somewhat arbitrarily for now.
 */
this.lightAngle = new Isomer.Vector(2, -1, 3).normalize();

So you could technically write iso.lightAngle = ... but it should accept from options.

As for color, I currently compute that in Isomer.prototype._addPath:

/**
 * Brightness is between -1 and 1 and is computed based
 * on the dot product between the light source vector and normal.
 */
var brightness = Vector.dotProduct(normal, this.lightAngle);

var color = baseColor.lighten(brightness * this.colorDifference);

I guess lighten sort of assumes the color is pure white. But for colored light I would have to add the two colors somehow. I'll look into it, thanks :)

[jdan]

Let me know if we need to make any improvements to this. Might be due for a vocabulary check...

[rcmaniac25]

Sure thing. Vocabulary is fine for now. Some of the terms aren't really needed unless you start to expand into lots of options for drawing.