sphere.java

Java mulitplayer strategy game. Adaptation of KDE Galaxy Conquest. (rules are changed - but still th

package net.sf.jawp.gui.client.semi3d;

/**
 * 
 * @author from javaworld
 * @version $Revision: 1.3 $
 * 
 */
public class Sphere implements Obj
{
	Texture texture;

	Light light;

	double sphereZ, sphereR;

	double c;

	public Sphere(final double sphereZ, final double sphereR,
			final Texture texture, final Light light)
	{
		this.sphereZ = sphereZ;
		this.sphereR = sphereR;
		this.texture = texture;
		this.light = light;
		c = sphereZ * sphereZ - sphereR * sphereR;
	}

	public RGB getIntersection(final Vec ray)
	{
		final double a = ray.x * ray.x + ray.y * ray.y + ray.z * ray.z;
		final double b = -2.0 * sphereZ * ray.z;
		final double tmp = b * b - 4.0 * a * c;
		if (tmp < 0)
		{
			return new RGB(0.0, 0.0, 0.0);
		}
		else
		{
			final double t = (-b - Math.sqrt(tmp)) / 2.0 / a;
			final Loc intersect = new Loc(ray.x * t, ray.y * t, ray.z * t);
			final double j = Math.asin(intersect.y / sphereR);
			final double i = Math.acos(intersect.x / sphereR / Math.cos(j));
			final RGB rgb = texture.getTexel(i / Math.PI, j / Math.PI + 0.5);

			final Vec norm = new Vec(intersect.x, intersect.y, intersect.z
					- sphereZ);
			final double length = norm.getLength();
			norm.scale(1.0 / length);
			final Vec dir = light.getDirection(intersect);
			final double coincidence = -norm.dot(dir);
			final double lighting = 0.25 + 0.75 * ((coincidence >= 0) ? coincidence
					: 0.0);
			rgb.scale(lighting);

			return rgb;
		}
	}
}