Plane.java

/*
 * gleem -- OpenGL Extremely Easy-To-Use Manipulators.
 * Copyright (C) 1998-2003 Kenneth B. Russell (kbrussel@alum.mit.edu)
 *
 * Copying, distribution and use of this software in source and binary
 * forms, with or without modification, is permitted provided that the
 * following conditions are met:
 *
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 * this list of conditions and the following disclaimer in the source
 * code header files; and Distributions of binary code must reproduce
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 * other materials provided with the software distribution.
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 * The names of Sun Microsystems, Inc. ("Sun") and/or the copyright
 * holder may not be used to endorse or promote products derived from
 * this software without specific prior written permission.
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 * KIND. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
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 */

package org.gephi.lib.gleem.linalg;

/** Represents a plane in 3D space. */

public class Plane {
  /** Normalized */
  private Vec3f normal;
  private Vec3f point;
  /** Constant for faster projection and intersection */
  float c;

  /** Default constructor initializes normal to (0, 1, 0) and point to
      (0, 0, 0) */
  public Plane() {
    normal = new Vec3f(0, 1, 0);
    point = new Vec3f(0, 0, 0);
    recalc();
  }

  /** Sets all parameters of plane. Plane has normal <b>normal</b> and
      goes through the point <b>point</b>. Normal does not need to be
      unit length but must not be the zero vector. */
  public Plane(Vec3f normal, Vec3f point) {
    this.normal = new Vec3f(normal);
    this.normal.normalize();
    this.point = new Vec3f(point);
    recalc();
  }

  /** Setter does some work to maintain internal caches. Normal does
      not need to be unit length but must not be the zero vector. */
  public void setNormal(Vec3f normal) {
    this.normal.set(normal);
    this.normal.normalize();
    recalc();
  }

  /** Normal is normalized internally, so <b>normal</b> is not
      necessarily equal to <code>plane.setNormal(normal);
      plane.getNormal();</code> */
  public Vec3f getNormal() {
    return normal;
  }

  /** Setter does some work to maintain internal caches */
  public void setPoint(Vec3f point) {
    this.point.set(point);
    recalc();
  }

  public Vec3f getPoint() {
    return point;
  }

  /** Project a point onto the plane */
  public void projectPoint(Vec3f pt,
                           Vec3f projPt) {
    float scale = normal.dot(pt) - c;
    projPt.set(pt.minus(normal.times(normal.dot(point) - c)));
  }

  /** Intersect a ray with the plane. Returns true if intersection occurred, false
      otherwise. This is a two-sided ray cast. */
  public boolean intersectRay(Vec3f rayStart,
                              Vec3f rayDirection,
                              IntersectionPoint intPt) {
    float denom = normal.dot(rayDirection);
    if (denom == 0)
      return false;
    intPt.setT((c - normal.dot(rayStart)) / denom);
    intPt.setIntersectionPoint(rayStart.plus(rayDirection.times(intPt.getT())));
    return true;
  }

  //----------------------------------------------------------------------
  // Internals only below this point
  //
  
  private void recalc() {
    c = normal.dot(point);
  }
}