82 lines
4.8 KiB
C#
82 lines
4.8 KiB
C#
//-----------------------------------------------------------------------
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//-----------------------------------------------------------------------
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// file="Log.cs"
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// Project: StgSharp
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// AuthorGroup: Nitload Space
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// Copyright (c) Nitload Space. All rights reserved.
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//
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// Permission is hereby granted, free of charge, to any person
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// obtaining a copy of this software and associated documentation
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// files (the “Software”), to deal in the Software without restriction,
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// including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software,
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// and to permit persons to whom the Software is furnished to do so,
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// subject to the following conditions:
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//
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// The above copyright notice and
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// this permission notice shall be included in all copies
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// or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED “AS IS”,
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// WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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// ARISING FROM, OUT OF OR IN CONNECTION WITH
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// THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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//
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//-----------------------------------------------------------------------
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//-----------------------------------------------------------------------
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using System;
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namespace StgSharp.Math
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{
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public static partial class Scaler
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{
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private static readonly float[] logArray = {
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0f, 0.00995033085316809f, 0.0198026272961797f, 0.0295588022415444f, 0.0392207131532813f, 0.048790164169432f, 0.0582689081239758f, 0.0676586484738149f, 0.0769610411361284f, 0.0861776962410524f, 0.0953101798043249f, 0.104360015324243f, 0.113328685307003f, 0.122217632724249f, 0.131028262406404f, 0.139761942375159f, 0.148420005118273f, 0.157003748809665f, 0.165514438477573f, 0.173953307123438f, 0.182321556793955f, 0.19062035960865f, 0.198850858745165f, 0.207014169384326f, 0.215111379616945f, 0.22314355131421f, 0.231111720963387f, 0.2390169004705f, 0.246860077931526f, 0.254642218373581f, 0.262364264467491f, 0.27002713721306f, 0.27763173659828f, 0.285178942233662f, 0.29266961396282f, 0.300104592450338f, 0.307484699747961f, 0.314810739840034f, 0.322083499169113f, 0.3293037471426f, 0.336472236621213f, 0.343589704390077f, 0.350656871613169f, 0.357674444271816f, 0.364643113587909f, 0.371563556432483f, 0.378436435720245f, 0.385262400790645f, 0.392042087776024f, 0.398776119957368f, 0.405465108108164f, 0.412109650826833f, 0.418710334858185f, 0.425267735404344f, 0.431782416425538f, 0.438254930931155f, 0.444685821261446f, 0.451075619360217f, 0.457424847038875f, 0.46373401623214f, 0.470003629245736f, 0.476234178996372f, 0.482426149244293f, 0.488580014818671f, 0.494696241836107f, 0.500775287912489f, 0.506817602368452f, 0.512823626428664f, 0.518793793415168f, 0.524728528934982f, 0.53062825106217f, 0.536493370514568f, 0.542324290825362f, 0.548121408509688f, 0.553885113226438f, 0.559615787935423f, 0.56531380905006f, 0.570979546585738f, 0.576613364303994f, 0.582215619852664f, 0.587786664902119f, 0.593326845277734f, 0.598836501088704f, 0.60431596685333f, 0.609765571620894f, 0.615185639090233f, 0.62057648772511f, 0.625938430866495f, 0.631271776841858f, 0.636576829071551f, 0.641853886172395f, 0.647103242058538f, 0.65232518603969f, 0.657520002916794f, 0.662687973075237f, 0.667829372575655f, 0.672944473242426f, 0.678033542749897f, 0.683096844706444f, 0.688134638736401f,
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};
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/// <summary>
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///
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/// </summary>
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/// <param _name="x"></param>
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/// <returns>
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/// Returns the value of ln(x).
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/// </returns>
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public static unsafe float Log( float x )
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{
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if( x < 0 ) {
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throw new ArgumentOutOfRangeException();
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}
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uint input = *( uint* )&x;
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int f = ( int )input;
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f >>= 23;
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f -= 127;
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input <<= 9;
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input >>= 9;
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input += 0b_0011_1111_1000_0000_0000_0000_0000_0000;
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float result = *( float* )&input;
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uint order = ( ( uint )( result * 100 ) ) - 100;
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float cache = ( result / ( 1f + ( 0.01f * order ) ) ) - 1;
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result = ( cache * ( -0.25f ) ) + 0.3333333333333f;
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result = ( result * cache ) - 0.5f;
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result = ( result * cache ) + 1.0f;
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result *= cache;
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return
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( f * 0.6931471806f ) + result + logArray[ order ];
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}
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public static float Log( float x, float y )
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{
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return Log( x ) / Log( y );
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}
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}
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}
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