Mega Code Archive
Remap a value specified relative to a pair of bounding values to the corresponding value relative to another pair of bou
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// Copyright (c) 2002-2003, Sony Computer Entertainment America
// Copyright (c) 2002-2003, Craig Reynolds <craig_reynolds@playstation.sony.com>
// Copyright (C) 2007 Bjoern Graf <bjoern.graf@gmx.net>
// Copyright (C) 2007 Michael Coles <michael@digini.com>
// All rights reserved.
//
// This software is licensed as described in the file license.txt, which
// you should have received as part of this distribution. The terms
// are also available at http://www.codeplex.com/SharpSteer/Project/License.aspx.
using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
namespace Bnoerj.AI.Steering
{
public class Utilities
{
static Random rng = new Random();
public static float Interpolate(float alpha, float x0, float x1)
{
return x0 + ((x1 - x0) * alpha);
}
public static Vector3 Interpolate(float alpha, Vector3 x0, Vector3 x1)
{
return x0 + ((x1 - x0) * alpha);
}
// ----------------------------------------------------------------------------
// Random number utilities
// Returns a float randomly distributed between 0 and 1
public static float Random()
{
return (float)rng.NextDouble();
}
// Returns a float randomly distributed between lowerBound and upperBound
public static float Random(float lowerBound, float upperBound)
{
return lowerBound + (Random() * (upperBound - lowerBound));
}
/// <summary>
/// Constrain a given value (x) to be between two (ordered) bounds min
/// and max.
/// </summary>
/// <param name="x"></param>
/// <param name="min"></param>
/// <param name="max"></param>
/// <returns>Returns x if it is between the bounds, otherwise returns the nearer bound.</returns>
public static float Clip(float x, float min, float max)
{
if (x < min) return min;
if (x > max) return max;
return x;
}
// ----------------------------------------------------------------------------
// remap a value specified relative to a pair of bounding values
// to the corresponding value relative to another pair of bounds.
// Inspired by (dyna:remap-interval y y0 y1 z0 z1)
public static float RemapInterval(float x, float in0, float in1, float out0, float out1)
{
// uninterpolate: what is x relative to the interval in0:in1?
float relative = (x - in0) / (in1 - in0);
// now interpolate between output interval based on relative x
return Interpolate(relative, out0, out1);
}
// Like remapInterval but the result is clipped to remain between
// out0 and out1
public static float RemapIntervalClip(float x, float in0, float in1, float out0, float out1)
{
// uninterpolate: what is x relative to the interval in0:in1?
float relative = (x - in0) / (in1 - in0);
// now interpolate between output interval based on relative x
return Interpolate(Clip(relative, 0, 1), out0, out1);
}
// ----------------------------------------------------------------------------
// classify a value relative to the interval between two bounds:
// returns -1 when below the lower bound
// returns 0 when between the bounds (inside the interval)
// returns +1 when above the upper bound
public static int IntervalComparison(float x, float lowerBound, float upperBound)
{
if (x < lowerBound) return -1;
if (x > upperBound) return +1;
return 0;
}
public static float ScalarRandomWalk(float initial, float walkspeed, float min, float max)
{
float next = initial + (((Random() * 2) - 1) * walkspeed);
if (next < min) return min;
if (next > max) return max;
return next;
}
public static float Square(float x)
{
return x * x;
}
/// <summary>
/// blends new values into an accumulator to produce a smoothed time series
/// </summary>
/// <remarks>
/// Modifies its third argument, a reference to the float accumulator holding
/// the "smoothed time series."
///
/// The first argument (smoothRate) is typically made proportional to "dt" the
/// simulation time step. If smoothRate is 0 the accumulator will not change,
/// if smoothRate is 1 the accumulator will be set to the new value with no
/// smoothing. Useful values are "near zero".
/// </remarks>
/// <typeparam name="T"></typeparam>
/// <param name="smoothRate"></param>
/// <param name="newValue"></param>
/// <param name="smoothedAccumulator"></param>
/// <example>blendIntoAccumulator (dt * 0.4f, currentFPS, smoothedFPS)</example>
public static void BlendIntoAccumulator(float smoothRate, float newValue, ref float smoothedAccumulator)
{
smoothedAccumulator = Interpolate(Clip(smoothRate, 0, 1), smoothedAccumulator, newValue);
}
public static void BlendIntoAccumulator(float smoothRate, Vector3 newValue, ref Vector3 smoothedAccumulator)
{
smoothedAccumulator = Interpolate(Clip(smoothRate, 0, 1), smoothedAccumulator, newValue);
}
}
}
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