1 files changed, 147 insertions, 0 deletions
diff --git a/hammer/noise.cpp b/hammer/noise.cpp
new file mode 100644
index 0000000..538eb38
--- /dev/null
+++ b/hammer/noise.cpp
@@ -0,0 +1,147 @@
+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: 
+//
+// $NoKeywords: $
+//=============================================================================//
+
+#include <stdafx.h>
+#include <math.h>
+
+#define OCTAVE_COUNT				4
+#define OCTAVE_COUNT_MINUS_ONE		OCTAVE_COUNT - 1
+
+//-----------------------------------------------------------------------------
+// quick random number generator - returns a value -1.0f to 1.0
+//-----------------------------------------------------------------------------
+float RandomNoise2D( int x, int y )
+{
+	int n = x + y * 57;
+	n = ( n << 13 ) ^ n;
+	
+	float value ( 1.0f - ( float )( ( n * ( n * n * 15731 + 789221 ) + 1376312589 ) & 0x7fffffff ) / 1073741824.0f );
+
+	return value;
+}
+
+
+//-----------------------------------------------------------------------------
+// Purpose:
+//-----------------------------------------------------------------------------
+float SmoothNoise2D( int x, int y )
+{
+	float corners = ( RandomNoise2D( x-1, y-1 ) + RandomNoise2D( x+1, y-1 ) + 
+		              RandomNoise2D( x-1, y+1 ) + RandomNoise2D( x+1, y+1 ) ) / 16.0f;
+	float sides = ( RandomNoise2D( x-1, y ) + RandomNoise2D( x+1, y ) +
+		            RandomNoise2D( x, y-1 ) + RandomNoise2D( x, y+1 ) ) / 8.0f;
+	float center = RandomNoise2D( x, y ) / 4.0f;
+	return corners + sides + center;
+}
+
+
+//-----------------------------------------------------------------------------
+// Purpose:
+//-----------------------------------------------------------------------------
+inline float InterpLinear( float a, float b, float x )
+{
+	return ( a * ( 1.0f - x ) + b * x );
+}
+
+
+//-----------------------------------------------------------------------------
+// Purpose:
+//-----------------------------------------------------------------------------
+inline float InterpCos( float a, float b, float x )
+{
+	float alpha = x * 3.1415927f; /* PI */
+	float frac = 1.0f - ( float )cos( alpha ) * 0.5f;
+	return ( a * ( 1.0f - frac ) + b * frac );
+}
+
+
+//-----------------------------------------------------------------------------
+// Purpose:
+//-----------------------------------------------------------------------------
+inline float InterpCubic( float a, float b, float c, float d, float x )
+{
+	float P = ( d - c ) - ( a - b );
+	float Q = ( a - b ) - P;
+	float R = ( c - a );
+	float S = b;
+
+	return ( ( P * x * 3.0f ) + ( Q * x * 2.0f ) + ( R * x ) + S );
+}
+  
+
+//-----------------------------------------------------------------------------
+// Purpose:
+//-----------------------------------------------------------------------------
+float InterpNoise2D( float x, float y )
+{
+	int iX = ( int )x;
+	float fracX = x - iX;
+
+	int iY = ( int )y;
+	float fracY = y - iY;
+
+	float n[4];
+	n[0] = SmoothNoise2D( iX, iY );
+	n[1] = SmoothNoise2D( iX+1, iY );
+	n[2] = SmoothNoise2D( iX, iY+1 );
+	n[3] = SmoothNoise2D( iX+1, iY+1 );
+
+	float interpX[2];
+	interpX[0] = InterpLinear( n[0], n[1], fracX );
+	interpX[1] = InterpLinear( n[2], n[3], fracX );
+
+	return InterpLinear( interpX[0], interpX[1], fracY );
+}
+
+//-----------------------------------------------------------------------------
+// Purpose:
+//   Input: x - 
+//          y -
+//          rockiness - 0.0f - 1.0f (0.0 = smooth, 1.0f = jagged)
+//  Output:
+//-----------------------------------------------------------------------------
+float PerlinNoise2D( float x, float y, float rockiness )
+{
+	float total = 0.0;
+	float persistence = rockiness;
+
+	for( int ndxOctave = 0; ndxOctave < OCTAVE_COUNT_MINUS_ONE; ndxOctave++ )
+	{
+		float frequency = ( float )pow( 2.f, ndxOctave );
+		float amplitude = ( float )pow( persistence, ndxOctave );
+	
+		total += InterpNoise2D( x * frequency, y * frequency ) * amplitude;
+	}
+
+	return total;
+}
+
+
+//-----------------------------------------------------------------------------
+// Purpose:
+//   Input: x - 
+//          y -
+//          rockiness - 0.0f - 1.0f (0.0 = smooth, 1.0f = jagged)
+//  Output: is between -1.0f and 1.0f
+//-----------------------------------------------------------------------------
+float PerlinNoise2DScaled( float x, float y, float rockiness )
+{
+	float total = 0.0;
+	float persistence = rockiness;
+
+	for( int ndxOctave = 0; ndxOctave < OCTAVE_COUNT_MINUS_ONE; ndxOctave++ )
+	{
+		float frequency = ( float )pow( 2.f, ndxOctave );
+		float amplitude = ( float )pow( persistence, ndxOctave );
+	
+		total += InterpNoise2D( x * frequency, y * frequency ) * amplitude;
+	}
+
+	total /= ( float )OCTAVE_COUNT;
+
+	return total;
+}