Light.java

package it.marteEngine.game.starcleaner;

import org.newdawn.slick.Color;

/**
 * A single light in the example. It's capable of determining how much effect it
 * will have in any given point on the tile map. Note that all coordinates are
 * given in pixel coordinates and not in tile coordinates.
 * 
 * @author kevin
 */
class Light {
	/** The x coordinate of the position the light has in the world */
	private float xpos;
	/** The y coordinate of the position the light has in the world */
	private float ypos;
	/**
	 * The intensity of the light, this specifies in pixels how far the light
	 * will shine
	 */
	private float intensity;
	/** The color the light should apply */
	private Color col;

	private LightMap lightMap;

	/**
	 * Create a new light in the world
	 * 
	 * @param x
	 *            The x coordinate of the position the light has in the world
	 * @param y
	 *            The y coordinate of the position the light has in the world
	 * @param str
	 *            The strength of the light, this specifies in pixels how far
	 *            the light will shine
	 * @param col
	 *            The color the light should apply
	 */
	public Light(float x, float y, float intensity, Color col) {
		xpos = x;
		ypos = y;
		this.intensity = intensity;
		this.col = col;
	}

	/**
	 * Set the location of the light in the world
	 * 
	 * @param x
	 *            The x coordinate of the position the light has in the world
	 * @param y
	 *            The y coordinate of the position the light has in the world
	 */
	public void setLocation(float x, float y) {
		xpos = x;
		ypos = y;
	}

	/**
	 * Get the effect the light should apply to a given location
	 * 
	 * @param x
	 *            The x coordinate of the location being considered for lighting
	 * @param y
	 *            The y coordinate of the location being considered for lighting
	 * @param colouredLights
	 *            True if we're supporting coloured lights
	 * 
	 * @return The effect on a given location of the light in terms of colour
	 *         components (all the same if we don't support coloured lights)
	 */
	public float[] getEffectAt(float x, float y, boolean colouredLights) {
		// first work out what propotion of the strength distance the light
		// is from the point. This is a value from 0-1 where 1 is the centre of
		// the
		// light (i.e. full brightness) and 0 is the very edge (or outside) the
		// lights
		// range
		float dx = (x - xpos);
		float dy = (y - ypos);
		float distance = (float) Math.hypot(dx, dy);
		float effect = 1.0f - (distance / intensity);

		if (effect < 0) {
			effect = 0;
		}
		if (effect > 1)
			effect = 1;
		// if we doing coloured lights then multiple the colour of the light by
		// the effect.
		// Otherwise just use calculated alpha and clear all color components
		if (colouredLights) {
			// when using colored, stop the falloff in the center so light can
			// be colored and not transparent
			float alpha = 1.0f - effect;
			if (alpha < 0)
				alpha = 0;
			return new float[] { col.r * effect, col.g * effect,
					col.b * effect, alpha };
		} else {
			return new float[] { 0, 0, 0, 1 - effect };
		}
	}

	public LightMap getLightMap() {
		return lightMap;
	}

	public void setLightMap(LightMap lightMap) {
		this.lightMap = lightMap;
	}
}