148 lines
4.3 KiB
C++
148 lines
4.3 KiB
C++
//========= Copyright Valve Corporation, All rights reserved. ============//
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//
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// Purpose:
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//
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// $NoKeywords: $
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//=============================================================================//
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#include <stdafx.h>
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#include <math.h>
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#define OCTAVE_COUNT 4
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#define OCTAVE_COUNT_MINUS_ONE OCTAVE_COUNT - 1
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//-----------------------------------------------------------------------------
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// quick random number generator - returns a value -1.0f to 1.0
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//-----------------------------------------------------------------------------
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float RandomNoise2D( int x, int y )
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{
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int n = x + y * 57;
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n = ( n << 13 ) ^ n;
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float value ( 1.0f - ( float )( ( n * ( n * n * 15731 + 789221 ) + 1376312589 ) & 0x7fffffff ) / 1073741824.0f );
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return value;
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}
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//-----------------------------------------------------------------------------
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// Purpose:
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//-----------------------------------------------------------------------------
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float SmoothNoise2D( int x, int y )
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{
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float corners = ( RandomNoise2D( x-1, y-1 ) + RandomNoise2D( x+1, y-1 ) +
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RandomNoise2D( x-1, y+1 ) + RandomNoise2D( x+1, y+1 ) ) / 16.0f;
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float sides = ( RandomNoise2D( x-1, y ) + RandomNoise2D( x+1, y ) +
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RandomNoise2D( x, y-1 ) + RandomNoise2D( x, y+1 ) ) / 8.0f;
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float center = RandomNoise2D( x, y ) / 4.0f;
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return corners + sides + center;
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}
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//-----------------------------------------------------------------------------
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// Purpose:
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//-----------------------------------------------------------------------------
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inline float InterpLinear( float a, float b, float x )
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{
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return ( a * ( 1.0f - x ) + b * x );
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}
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//-----------------------------------------------------------------------------
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// Purpose:
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//-----------------------------------------------------------------------------
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inline float InterpCos( float a, float b, float x )
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{
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float alpha = x * 3.1415927f; /* PI */
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float frac = 1.0f - ( float )cos( alpha ) * 0.5f;
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return ( a * ( 1.0f - frac ) + b * frac );
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}
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//-----------------------------------------------------------------------------
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// Purpose:
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//-----------------------------------------------------------------------------
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inline float InterpCubic( float a, float b, float c, float d, float x )
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{
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float P = ( d - c ) - ( a - b );
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float Q = ( a - b ) - P;
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float R = ( c - a );
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float S = b;
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return ( ( P * x * 3.0f ) + ( Q * x * 2.0f ) + ( R * x ) + S );
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}
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//-----------------------------------------------------------------------------
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// Purpose:
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//-----------------------------------------------------------------------------
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float InterpNoise2D( float x, float y )
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{
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int iX = ( int )x;
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float fracX = x - iX;
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int iY = ( int )y;
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float fracY = y - iY;
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float n[4];
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n[0] = SmoothNoise2D( iX, iY );
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n[1] = SmoothNoise2D( iX+1, iY );
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n[2] = SmoothNoise2D( iX, iY+1 );
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n[3] = SmoothNoise2D( iX+1, iY+1 );
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float interpX[2];
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interpX[0] = InterpLinear( n[0], n[1], fracX );
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interpX[1] = InterpLinear( n[2], n[3], fracX );
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return InterpLinear( interpX[0], interpX[1], fracY );
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}
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//-----------------------------------------------------------------------------
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// Purpose:
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// Input: x -
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// y -
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// rockiness - 0.0f - 1.0f (0.0 = smooth, 1.0f = jagged)
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// Output:
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//-----------------------------------------------------------------------------
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float PerlinNoise2D( float x, float y, float rockiness )
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{
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float total = 0.0;
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float persistence = rockiness;
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for( int ndxOctave = 0; ndxOctave < OCTAVE_COUNT_MINUS_ONE; ndxOctave++ )
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{
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float frequency = ( float )pow( 2.f, ndxOctave );
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float amplitude = ( float )pow( persistence, ndxOctave );
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total += InterpNoise2D( x * frequency, y * frequency ) * amplitude;
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}
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return total;
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}
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//-----------------------------------------------------------------------------
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// Purpose:
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// Input: x -
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// y -
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// rockiness - 0.0f - 1.0f (0.0 = smooth, 1.0f = jagged)
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// Output: is between -1.0f and 1.0f
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//-----------------------------------------------------------------------------
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float PerlinNoise2DScaled( float x, float y, float rockiness )
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{
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float total = 0.0;
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float persistence = rockiness;
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for( int ndxOctave = 0; ndxOctave < OCTAVE_COUNT_MINUS_ONE; ndxOctave++ )
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{
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float frequency = ( float )pow( 2.f, ndxOctave );
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float amplitude = ( float )pow( persistence, ndxOctave );
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total += InterpNoise2D( x * frequency, y * frequency ) * amplitude;
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}
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total /= ( float )OCTAVE_COUNT;
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return total;
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}
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