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 * Copyright (c) 2013, Daniel Murphy
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package org.jbox2d.common;

/**
 * Global tuning constants based on MKS units and various integer maximums (vertices per shape,
 * pairs, etc.).
 */
public class Settings {

  /** A "close to zero" float epsilon value for use */
  public static final float EPSILON = 1.1920928955078125E-7f;

  /** Pi. */
  public static final float PI = (float) Math.PI;

  // JBox2D specific settings
  public static boolean FAST_ABS = true;
  public static boolean FAST_FLOOR = true;
  public static boolean FAST_CEIL = true;
  public static boolean FAST_ROUND = true;
  public static boolean FAST_ATAN2 = true;
  public static boolean FAST_POW = true;
  public static int CONTACT_STACK_INIT_SIZE = 10;
  public static boolean SINCOS_LUT_ENABLED = true;
  /**
   * smaller the precision, the larger the table. If a small table is used (eg, precision is .006 or
   * greater), make sure you set the table to lerp it's results. Accuracy chart is in the MathUtils
   * source. Or, run the tests yourself in {@link SinCosTest}.
 
 Good lerp precision
   * values:
   * 
   * .0092
   * .008201
   * .005904
   * .005204
   * .004305
   * .002807
   * .001508
   * 9.32500E-4
   * 7.48000E-4
   * 8.47000E-4
   * .0005095
   * .0001098
   * 9.50499E-5
   * 6.08500E-5
   * 3.07000E-5
   * 1.53999E-5
   * 
   */
  public static final float SINCOS_LUT_PRECISION = .00011f;
  public static final int SINCOS_LUT_LENGTH = (int) Math.ceil(Math.PI * 2 / SINCOS_LUT_PRECISION);
  /**
   * Use if the table's precision is large (eg .006 or greater). Although it is more expensive, it
   * greatly increases accuracy. Look in the MathUtils source for some test results on the accuracy
   * and speed of lerp vs non lerp. Or, run the tests yourself in {@link SinCosTest}.
   */
  public static boolean SINCOS_LUT_LERP = false;


  // Collision

  /**
   * The maximum number of contact points between two convex shapes.
   */
  public static int maxManifoldPoints = 2;

  /**
   * The maximum number of vertices on a convex polygon.
   */
  public static int maxPolygonVertices = 8;

  /**
   * This is used to fatten AABBs in the dynamic tree. This allows proxies to move by a small amount
   * without triggering a tree adjustment. This is in meters.
   */
  public static float aabbExtension = 0.1f;

  /**
   * This is used to fatten AABBs in the dynamic tree. This is used to predict the future position
   * based on the current displacement. This is a dimensionless multiplier.
   */
  public static float aabbMultiplier = 2.0f;

  /**
   * A small length used as a collision and constraint tolerance. Usually it is chosen to be
   * numerically significant, but visually insignificant.
   */
  public static float linearSlop = 0.005f;

  /**
   * A small angle used as a collision and constraint tolerance. Usually it is chosen to be
   * numerically significant, but visually insignificant.
   */
  public static float angularSlop = (2.0f / 180.0f * PI);

  /**
   * The radius of the polygon/edge shape skin. This should not be modified. Making this smaller
   * means polygons will have and insufficient for continuous collision. Making it larger may create
   * artifacts for vertex collision.
   */
  public static float polygonRadius = (2.0f * linearSlop);

  /** Maximum number of sub-steps per contact in continuous physics simulation. */
  public static int maxSubSteps = 8;

  // Dynamics

  /**
   * Maximum number of contacts to be handled to solve a TOI island.
   */
  public static int maxTOIContacts = 32;

  /**
   * A velocity threshold for elastic collisions. Any collision with a relative linear velocity
   * below this threshold will be treated as inelastic.
   */
  public static float velocityThreshold = 1.0f;

  /**
   * The maximum linear position correction used when solving constraints. This helps to prevent
   * overshoot.
   */
  public static float maxLinearCorrection = 0.2f;

  /**
   * The maximum angular position correction used when solving constraints. This helps to prevent
   * overshoot.
   */
  public static float maxAngularCorrection = (8.0f / 180.0f * PI);

  /**
   * The maximum linear velocity of a body. This limit is very large and is used to prevent
   * numerical problems. You shouldn't need to adjust this.
   */
  public static float maxTranslation = 2.0f;
  public static float maxTranslationSquared = (maxTranslation * maxTranslation);

  /**
   * The maximum angular velocity of a body. This limit is very large and is used to prevent
   * numerical problems. You shouldn't need to adjust this.
   */
  public static float maxRotation = (0.5f * PI);
  public static float maxRotationSquared = (maxRotation * maxRotation);

  /**
   * This scale factor controls how fast overlap is resolved. Ideally this would be 1 so that
   * overlap is removed in one time step. However using values close to 1 often lead to overshoot.
   */
  public static float baumgarte = 0.2f;
  public static float toiBaugarte = 0.75f;


  // Sleep

  /**
   * The time that a body must be still before it will go to sleep.
   */
  public static float timeToSleep = 0.5f;

  /**
   * A body cannot sleep if its linear velocity is above this tolerance.
   */
  public static float linearSleepTolerance = 0.01f;

  /**
   * A body cannot sleep if its angular velocity is above this tolerance.
   */
  public static float angularSleepTolerance = (2.0f / 180.0f * PI);

  // Particle

  /**
   * A symbolic constant that stands for particle allocation error.
   */
  public static final int invalidParticleIndex = (-1);

  /**
   * The standard distance between particles, divided by the particle radius.
   */
  public static final float particleStride = 0.75f;

  /**
   * The minimum particle weight that produces pressure.
   */
  public static final float minParticleWeight = 1.0f;

  /**
   * The upper limit for particle weight used in pressure calculation.
   */
  public static final float maxParticleWeight = 5.0f;

  /**
   * The maximum distance between particles in a triad, divided by the particle radius.
   */
  public static final int maxTriadDistance = 2;
  public static final int maxTriadDistanceSquared = (maxTriadDistance * maxTriadDistance);

  /**
   * The initial size of particle data buffers.
   */
  public static final int minParticleBufferCapacity = 256;


  /**
   * Friction mixing law. Feel free to customize this. TODO djm: add customization
   * 
   * @param friction1
   * @param friction2
   * @return
   */
  public static float mixFriction(float friction1, float friction2) {
    return MathUtils.sqrt(friction1 * friction2);
  }

  /**
   * Restitution mixing law. Feel free to customize this. TODO djm: add customization
   * 
   * @param restitution1
   * @param restitution2
   * @return
   */
  public static float mixRestitution(float restitution1, float restitution2) {
    return restitution1 > restitution2 ? restitution1 : restitution2;
  }
}