/* Copyright (C) 2001, 2007 United States Government as represented by
the Administrator of the National Aeronautics and Space Administration.
All Rights Reserved.
*/
package gov.nasa.worldwind.layers;

import gov.nasa.worldwind.geom.Position;
import gov.nasa.worldwind.layers.RenderableLayer;
import gov.nasa.worldwind.render.DrawContext;
import gov.nasa.worldwind.util.Logging;

import javax.media.opengl.GL;
import java.awt.*;

/**
 * Sets fog range/density according to view altitude.
 * 
 * @Author: Patrick Murris
 * @version $Id: FogLayer.java 5178 2008-04-25 21:51:20Z patrickmurris $
 */
public class FogLayer  extends RenderableLayer {

    private float fogColor[] = new float[] { 0.66f, 0.70f, 0.81f, 1.0f };
    private float nearFactor = 1.1f;  // Applies to the view altitude
    private float farFactor = 1.1f;   // Applies to the distance to the horizon

    /**
     * Sets fog range/density according to view altitude
     */
    public FogLayer() {
        this.setName(Logging.getMessage("layers.Earth.FogLayer.Name"));
    }

    // Public properties

    /**
     * Get the fog color
     * @return the fog color
     */
    public Color getColor()
    {
        return new Color(this.fogColor[0], this.fogColor[1], this.fogColor[2], this.fogColor[3]);
    }

    /**
     * Set the fog color
     * @param color the fog color
     */
    public void setColor(Color color)
    {
        if (color == null)
        {
            String msg = Logging.getMessage("nullValue.ColorIsNull");
            Logging.logger().severe(msg);
            throw new IllegalArgumentException(msg);
        }
        color.getColorComponents(this.fogColor);
    }

    /**
     * Get the near distance factor that is applied to the view altitude.
     * @return the near factor
     */
    public float getNearFactor()
    {
        return this.nearFactor;
    }

    /**
     * Set the near distance factor applied to the view altitude
     * @param factor the factor to apply to the view altitude
     */
    public void setNearFactor(float factor)
    {
        this.nearFactor = factor;
    }

    /**
     * Get the far distance factor that is applied to the eye distance to the horizon.
     * @return the far factor
     */
    public float getFarFactor()
    {
        return this.farFactor;
    }

    /**
     * Set the far distance factor applied to the eye distance to the horizon
     * @param factor the factor to apply to the eye distance to the horizon
     */
    public void setFarFactor(float factor)
    {
        this.farFactor = factor;
    }

    // Rendering
    
    /**
     * Setup fog
     * @param dc the current DrawContext
     */
    public void doRender(DrawContext dc)
    {
        Position eyePos = dc.getView().getEyePosition();
        if (eyePos == null)
            return;
        // View altitude
        float alt = (float)eyePos.getElevation();
        alt = alt < 100 ? 100 : alt;   // Clamp altitudes below 100m
        // Start based on view altitude
        float start = alt * this.nearFactor;
        // End based on distance to horizon
        float end = (float)(dc.getView().computeHorizonDistance() * this.farFactor);
        // Set GL fog
        GL gl = dc.getGL();
        gl.glFogfv(GL.GL_FOG_COLOR, fogColor, 0);  // Set fog color
        gl.glFogi(GL.GL_FOG_MODE, GL.GL_LINEAR);   // Set fog mode
        gl.glFogf(GL.GL_FOG_START, start);         // Set fog start distance
        gl.glFogf(GL.GL_FOG_END, end);             // Set fog end distance
        gl.glHint(GL.GL_FOG_HINT, GL.GL_DONT_CARE);// Set fog hint
        gl.glEnable(GL.GL_FOG);                    // Enable fog

    }

    @Override
    public String toString()
    {
        return this.getName();
    }


}