1 files changed, 108 insertions, 0 deletions
diff --git a/engine/sound_shared.cpp b/engine/sound_shared.cpp
new file mode 100644
index 0000000..659eb17
--- /dev/null
+++ b/engine/sound_shared.cpp
@@ -0,0 +1,108 @@
+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: Sound code shared between server and client 
+//
+//=============================================================================//
+
+
+#include <math.h>
+
+#include "convar.h"
+#include "sound.h"
+
+ConVar snd_refdist( "snd_refdist", "36", FCVAR_CHEAT);
+ConVar snd_refdb( "snd_refdb", "60", FCVAR_CHEAT );
+ConVar snd_foliage_db_loss( "snd_foliage_db_loss", "4", FCVAR_CHEAT ); 
+ConVar snd_gain( "snd_gain", "1", FCVAR_CHEAT );
+ConVar snd_gain_max( "snd_gain_max", "1", FCVAR_CHEAT );
+ConVar snd_gain_min( "snd_gain_min", "0.01", FCVAR_CHEAT );
+
+// calculate gain based on atmospheric attenuation.
+// as gain excedes threshold, round off (compress) towards 1.0 using spline
+#define SND_GAIN_COMP_EXP_MAX	2.5f	// Increasing SND_GAIN_COMP_EXP_MAX fits compression curve more closely
+										// to original gain curve as it approaches 1.0.  
+#define SND_GAIN_COMP_EXP_MIN	0.8f	
+
+#define SND_GAIN_COMP_THRESH	0.5f		// gain value above which gain curve is rounded to approach 1.0
+
+#define SND_DB_MAX				140.0f	// max db of any sound source
+#define SND_DB_MED				90.0f	// db at which compression curve changes
+
+#define SNDLVL_TO_DIST_MULT( sndlvl ) ( sndlvl ? ((pow( 10.0f, snd_refdb.GetFloat() / 20 ) / pow( 10.0f, (float)sndlvl / 20 )) / snd_refdist.GetFloat()) : 0 )
+#define DIST_MULT_TO_SNDLVL( dist_mult ) (soundlevel_t)(int)( dist_mult ? ( 20 * log10( pow( 10.0f, snd_refdb.GetFloat() / 20 ) / (dist_mult * snd_refdist.GetFloat()) ) ) : 0 )
+
+
+
+float SND_GetGainFromMult( float gain, float dist_mult, vec_t dist )
+{
+	// test additional attenuation
+	// at 30c, 14.7psi, 60% humidity, 1000Hz == 0.22dB / 100ft.
+	// dense foliage is roughly 2dB / 100ft
+
+	float additional_dB_loss = snd_foliage_db_loss.GetFloat() * (dist / 1200);
+	float additional_dist_mult = pow( 10.0f, additional_dB_loss / 20);
+
+	float relative_dist = dist * dist_mult * additional_dist_mult;
+
+	// hard code clamp gain to 10x normal (assumes volume and external clipping)
+
+	if (relative_dist > 0.1)
+	{
+		gain *= (1/relative_dist);
+	}
+	else
+		gain *= 10.0;
+
+	// if gain passess threshold, compress gain curve such that gain smoothly approaches 1.0
+
+	if ( gain > SND_GAIN_COMP_THRESH )
+	{
+		float snd_gain_comp_power = SND_GAIN_COMP_EXP_MAX;
+		soundlevel_t sndlvl = DIST_MULT_TO_SNDLVL( dist_mult );
+		float Y;
+		
+		// decrease compression curve fit for higher sndlvl values
+
+		if ( sndlvl > SND_DB_MED )
+		{
+			// snd_gain_power varies from max to min as sndlvl varies from 90 to 140
+
+			snd_gain_comp_power = RemapVal ((float)sndlvl, SND_DB_MED, SND_DB_MAX, SND_GAIN_COMP_EXP_MAX, SND_GAIN_COMP_EXP_MIN);
+		}
+
+		// calculate crossover point
+
+		Y = -1.0 / ( pow(SND_GAIN_COMP_THRESH, snd_gain_comp_power) * (SND_GAIN_COMP_THRESH - 1) );
+		
+		// calculate compressed gain
+
+		gain = 1.0 - 1.0 / (Y * pow( gain, snd_gain_comp_power ) );
+
+		gain = gain * snd_gain_max.GetFloat();
+	}
+
+	if ( gain < snd_gain_min.GetFloat() )
+	{
+		// sounds less than snd_gain_min fall off to 0 in distance it took them to fall to snd_gain_min
+
+		gain = snd_gain_min.GetFloat() * (2.0 - relative_dist * snd_gain_min.GetFloat());
+		
+		if (gain <= 0.0)
+			gain = 0.001;	// don't propagate 0 gain
+	}
+
+	return gain;
+}
+
+float S_GetGainFromSoundLevel( soundlevel_t soundlevel, vec_t dist )
+{
+	float gain = snd_gain.GetFloat();
+
+	float dist_mult = SNDLVL_TO_DIST_MULT( soundlevel );
+	if ( dist_mult )
+	{
+		gain = SND_GetGainFromMult( gain, dist_mult, dist );
+	}
+
+	return gain;
+}