/**
 *
 * Copyright (c) 2014, the Railo Company Ltd. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either 
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public 
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 * 
 **/
/*
*

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package lucee.runtime.img.math;

public class FBM implements Function2D {

	protected float[] exponents;
	protected float H;
	protected float lacunarity;
	protected float octaves;
	protected Function2D basis;

	public FBM(float H, float lacunarity, float octaves) {
		this(H, lacunarity, octaves, new Noise());
	}
	
	public FBM(float H, float lacunarity, float octaves, Function2D basis) {
		this.H = H;
		this.lacunarity = lacunarity;
		this.octaves = octaves;
		this.basis = basis;

		exponents = new float[(int)octaves+1];
		float frequency = 1.0f;
		for (int i = 0; i <= (int)octaves; i++) {
			exponents[i] = (float)Math.pow(frequency, -H);
			frequency *= lacunarity;
		}
	}

	public void setBasis(Function2D basis) {
		this.basis = basis;
	}

	public Function2D getBasisType() {
		return basis;
	}

	@Override
	public float evaluate(float x, float y) {
		float value = 0.0f;
		float remainder;
		int i;
		
		// to prevent "cascading" effects
		x += 371;
		y += 529;
		
		for (i = 0; i < (int)octaves; i++) {
			value += basis.evaluate(x, y) * exponents[i];
			x *= lacunarity;
			y *= lacunarity;
		}

		remainder = octaves - (int)octaves;
		if (remainder != 0)
			value += remainder * basis.evaluate(x, y) * exponents[i];

		return value;
	}

}