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Minecraft mapping and rendering tool

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/* Copyright (c) 2012 Jesper Öqvist 
 *
 * This file is part of Chunky.
 *
 * Chunky is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Chunky 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 General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with Chunky.  If not, see .
 */
package se.llbit.math;

/**
 * A double-sided quad
 *
 * @author Jesper Öqvist 
 */
public class DoubleSidedQuad extends Quad {

  private DoubleSidedQuad(Quad other, Transform t) {
    super(other, t);
  }

  public DoubleSidedQuad(Vector3 p1, Vector3 p2, Vector3 p3, Vector4 uv) {
    super(p1, p2, p3, uv);
  }

  @Override public boolean intersect(Ray ray) {
    double ix = ray.o.x - QuickMath.floor(ray.o.x + ray.d.x * Ray.OFFSET);
    double iy = ray.o.y - QuickMath.floor(ray.o.y + ray.d.y * Ray.OFFSET);
    double iz = ray.o.z - QuickMath.floor(ray.o.z + ray.d.z * Ray.OFFSET);
    double denom = ray.d.dot(n);
    double u, v;

    if (QuickMath.abs(denom) > Ray.EPSILON) {
      double t = -(ix * n.x + iy * n.y + iz * n.z + d) / denom;
      if (t > -Ray.EPSILON && t < ray.t) {
        ix = ix + ray.d.x * t - o.x;
        iy = iy + ray.d.y * t - o.y;
        iz = iz + ray.d.z * t - o.z;
        u = ix * xv.x + iy * xv.y + iz * xv.z;
        u *= xvl;
        v = ix * yv.x + iy * yv.y + iz * yv.z;
        v *= yvl;
        if (u >= 0 && u <= 1 && v >= 0 && v <= 1) {
          ray.u = uv.x + u * uv.y;
          ray.v = uv.z + v * uv.w;
          ray.tNext = t;
          return true;
        }
      }
    }
    return false;
  }

  /**
   * Build a transformed copy of this quad.
   */
  @Override public DoubleSidedQuad transform(Transform transform) {
    return new DoubleSidedQuad(this, transform);
  }
}