Curve.java

/**
 * Copyright 2008 - 2015 The Loon Game Engine Authors
 * 
 * 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.
 * 
 * @project loon
 * @author cping
 * @email：javachenpeng@yahoo.com
 * @version 0.5
 */
package loon.geom;

public class Curve extends Shape {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	private Vector2f p1;

	private Vector2f c1;

	private Vector2f c2;

	private Vector2f p2;

	private int segments;

	public Curve(Vector2f p1, Vector2f c1, Vector2f c2, Vector2f p2) {
		this(p1, c1, c2, p2, 20);
	}

	public Curve(Vector2f p1, Vector2f c1, Vector2f c2, Vector2f p2,
			int segments) {
		this.p1 = new Vector2f(p1);
		this.c1 = new Vector2f(c1);
		this.c2 = new Vector2f(c2);
		this.p2 = new Vector2f(p2);
		this.segments = segments;
		pointsDirty = true;
	}

	public Vector2f pointAt(float t) {
		float a = 1 - t;
		float b = t;

		float f1 = a * a * a;
		float f2 = 3 * a * a * b;
		float f3 = 3 * a * b * b;
		float f4 = b * b * b;

		float nx = (p1.x * f1) + (c1.x * f2) + (c2.x * f3) + (p2.x * f4);
		float ny = (p1.y * f1) + (c1.y * f2) + (c2.y * f3) + (p2.y * f4);

		return new Vector2f(nx, ny);
	}

	protected void createPoints() {
		float step = 1.0f / segments;
		points = new float[(segments + 1) * 2];
		for (int i = 0; i < segments + 1; i++) {
			float t = i * step;

			Vector2f p = pointAt(t);
			points[i * 2] = p.x;
			points[(i * 2) + 1] = p.y;
		}
	}

	public Shape transform(Matrix3 transform) {
		float[] pts = new float[8];
		float[] dest = new float[8];
		pts[0] = p1.x;
		pts[1] = p1.y;
		pts[2] = c1.x;
		pts[3] = c1.y;
		pts[4] = c2.x;
		pts[5] = c2.y;
		pts[6] = p2.x;
		pts[7] = p2.y;
		transform.transform(pts, 0, dest, 0, 4);

		return new Curve(new Vector2f(dest[0], dest[1]), new Vector2f(dest[2],
				dest[3]), new Vector2f(dest[4], dest[5]), new Vector2f(dest[6],
				dest[7]));
	}

	public boolean closed() {
		return false;
	}
}